Polymer and method of making same
阅读说明：本技术 聚合物 (Polymer and method of making same ) 是由 史蒂文·兰纳德 皮埃尔·尚邦 萨万娜·卡森 于 2018-04-26 设计创作，主要内容包括：一种制备聚合物的方法,包括使用自由基乙烯基聚合形成聚合物的碳-碳主链链段,其中聚合物中的最长链包含间插其它化学基团和/化学链的乙烯基聚合物链。产物具有包含通过乙烯基聚合形成的多官能逐步增长单体残基的混合物的逐步增长聚合物的特征。(A method of preparing a polymer comprising forming a carbon-carbon backbone segment of the polymer using free radical vinyl polymerization, wherein the longest chain in the polymer comprises vinyl polymer chains interspersed with other chemical groups and/or chains. The product has the characteristics of a step-growth polymer comprising a mixture of multifunctional step-growth monomer residues formed by vinyl polymerization.)
1. a method of making a polymer comprising forming a carbon-carbon backbone segment of the polymer using free radical vinyl polymerization, wherein the longest chain in the polymer comprises vinyl polymer chains interspersed with other chemical groups and/or chains.
2. A method of making a polymer comprising forming a carbon-carbon segment of a step-growth monomer residue using free radical vinyl polymerization.
3. The method of claim 1 or claim 2, wherein the polymer is a branched polymer, and wherein the branching points are in the vinyl polymer chain.
4. The method of any preceding claim, comprising free radical polymerization of a polyvinyl monomer.
5. The process of any one of the preceding claims, comprising free radical polymerization of a divinyl monomer.
6. The method of any preceding claim, wherein the polymer is a polyester.
7. The method of claim 6 wherein the polyvinyl monomer is a polyacrylate, a polymethacrylate, or a polyvinyl polyester.
8. The method of claim 6, wherein the divinyl monomer is a diacrylate, dimethacrylate, or divinyl diester.
9. The method of any one of claims 1-5, wherein the polymer is a polyamide.
10. The method of claim 9, wherein the polyvinyl monomer is a polyacrylamide, polymethacrylamide, or polyvinylpolyamide.
11. The method of claim 9, wherein the divinyl monomer is a bisacrylamide, a dimethylacrylamide, or a divinyldiamide.
12. The method of any one of claims 1-5, wherein the polymer is a phenylene-containing polymer, such as polyalkylphenylene or polyphenylene ether.
13. The method of claim 12 wherein the polyvinyl monomer is polyvinyl benzene.
14. The process of claim 12, wherein the divinyl monomer is divinylbenzene.
15. The method of any one of claims 1-5, wherein the polymer is a polycarbonate.
16. The method according to claim 15, wherein the polyvinyl monomer, such as a divinyl monomer, comprises one or two carbonate groups between double bonds.
17. The process of any one of the preceding claims, comprising introducing a divinyl monomer and a lesser amount of a monovinyl monomer.
18. A method according to any one of claims 1 to 16, comprising introducing not only one or more polyvinyl monomers but also monovinyl monomers, wherein 10% or more of the vinyl monomers used are polyvinyl monomers.
19. The method of any one of the preceding claims, comprising introducing a plurality of divinyl monomers.
20. The method of any one of the preceding claims, comprising introducing a trivinyl monomer and a divinyl monomer and/or a monovinyl monomer.
21. A polymer obtainable by the process of any one of the preceding claims.
22. A branched polymer comprising vinyl polymer chains, wherein the vinyl polymer chains comprise residues of the vinyl group of a divinyl monomer, and wherein the longest chains in the polymer are not the vinyl polymer chains but extend through linkages between double bonds of the divinyl monomer.
23. A branched polymer comprising vinyl polymer chains, wherein the vinyl polymer chains comprise the residue of the vinyl groups of a polyvinyl monomer, and wherein the longest chains in the polymer are not the vinyl polymer chains but extend through the linkages between the double bonds of the polyvinyl monomer.
24. A step-growth polymer comprising a mixture of multifunctional step-growth monomer residues formed by vinyl polymerization.
Technical Field
The present invention relates to polymers and to a process for their preparation. The class of materials to which the present invention relates includes polymers conventionally prepared by step-growth polymerization, including polyamides, polyesters, polyphenylenes and polycarbonates. In particular, the present invention relates to branched polymers (branchedpolymers).
Background
Step growth polymerization methods are well known and widely used to prepare a range of polymers. They require monomer reaction to form small fragments, which are then reacted (with other small fragments or with monomers) to form larger oligomers and ultimately higher molecular weight polymers.
Step-growth polymers may use two difunctional monomers ("A2"and" B2") for example, diols and diacids, wherein the desired polymeric product is a polyester. A. the2And B2The monomers may be reacted together to form a-B units. The A-B unit may then be reacted with A2Monomer, B2Monomers, another A-B unit or longer chains, e.g., A-B-A-B-A-B, to form A-B-A, B-A-B, A-B-A-B or A-B-A-B-A-B-A-B, respectively.
Step-growth polymers may also be formed starting from A-B units that are reactive with other A-B units or longer segments.
Certain types of ring opening reactions can be used in step-growth polymerization processes. For example, lactones may be used as monomers and subjected to Ring Opening Polymerization (ROP) to form polyesters. Wherein the backbone of one type will correspond to the backbone in the diol monomer and the backbone of the second type will correspond to the A of the backbone in the diacid monomer2+B2Systems in contrast, such systems will generally produce a type of backbone between the ester groups of the polymer.
The step-growth polymerization process has several inherent problems. Generally speaking, step-growth polymerization processes can form high molecular weight polymers only at very high conversions. This is known since the pioneering work of Carothers in the early 20 th century. Carothers indicated a mathematical relationship of number average degree of polymerization of 1/(1-p), where p is the fractional range of reaction. Thus, for example, at 75% conversion, under theoretical conditions the number average degree of polymerization will be 1/(1-0.75) ═ 4, which is too low to be suitable for most applications. 99% conversion is required to achieve 100 number average degree of polymerization.
In many cases, the need for high conversion is itself a problem, but, in addition, in A2+B2In the case of systems, subtle changes in stoichiometric conditions are very detrimental because they limit the amount of conversion possible. On an industrial scale, however, it is difficult to achieve precise stoichiometry.
Many of the reactions involved are in equilibrium and depolymerization or scrambling (e.g., by transesterification) occurs, thus requiring specific conditions to obtain the desired product. Some reactions are condensation reactions and require the removal of by-products (usually water). High temperatures and/or catalysis (typically metal catalysis) are often required. Due to the reactivity of the monomers, it can be difficult to control the reaction: for example, monomers for ROP are inherently susceptible to ring opening.
Additional complications also arise when preparing branched polymers. These require the use of at least one trifunctional or higher-functional monomer, e.g. A3、B3、AB2Or A2B. Using A3Or B3(or n is A of 3 or more)nOr BnMonomer) generally results in rapid gelation. This satisfies the modified Carothers equation according to which the number average degree of polymerization is 2/(2-pf), where p is the fractional range of the reaction and f is the average functionality of the monomer units. Thus, for example, for A3And B3The system, f is 3, and infinite number average degree of polymerization (or gelation) occurs at two-thirds conversion. When using higher functionality AnOr BnWith monomers, gelation can occur at much lower conversion rates.
ABnOr AnThe use of B monomers allows ungelled branched or hyperbranched systems to be formed, but such monomers are generally less readily available or require specialized generation, and if available, are also availableThere may be other problems associated with step-growth polymerization.
To the extent that it is possible to adhere to the "thinking set" of the chemical industry with respect to step-growth polymers, it can be said that such polymers would bring such significant benefits and have been widely used in many important commercial applications, such that the skilled person would not normally question whether a step-growth polymerization reaction is to be used, but would have accepted its disadvantages.
In the last forty years, the global interest in highly and ideally branched polymers has steadily increased, with renewed interest in hyperbranched polymers and the introduction of dendrimers (dendrimers) in the 80 s of the 19 th century. While dendrimers are nominally perfectly branched unimolecular structures, hyperbranched polymers are typically dispersed products produced by a single-step reaction, resulting in limited structural or chemical homogeneity. Hyperbranched polymers also provide relatively low branching compared to dendritic polymers. Dendrimers are described as "organic chemistry methods of branched polymers" due to the use of repeated high yield coupling chemistry plus purification steps and the reported formation of structurally pure end products; such synthetic complexity inevitably leads to high costs, and the ideal dendrimer is prohibitively expensive in view of the relatively profitable small batch applications that can justify the additional costs of changing properties in steps. Hyperbranched polymers also offer considerable benefits compared to linear polymers, such as reduced melt/solution viscosity and high solubility.
Commercially, branched polymers with different chemistries are very important and include:
Some branched polymers are crosslinked or gelled, while others are soluble and non-gelled. The present invention relates generally to polymers belonging to the latter group.
The properties and potential applications of branched polymers are determined by several characteristics, including the structure of the polymers, the type of monomers from which they are made, the type of polymerization, the degree of branching, the functional groups on the polymers, the use of other reagents, and the conditions under which the polymerization is carried out. These properties, in turn, can affect the hydrophobicity, viscosity, solubility of the polymer or portions thereof, as well as the form and behavior of the polymer at the nanoparticle level, in bulk, and in solution.
Vinyl polymers are a group of polymers different from step-growth polymers.
To avoid extensive crosslinking and gelling, control of the level of branching within vinyl polymers has been achieved using various methods. For example, the "Strathclyde route" in N.O' Brien, A.McKee, D.C.Sherrington, A.T.Slark, A.Titterton, Polymer2000,41, 6027-Astro 6031 relates to controlled radical polymerization of predominantly monofunctional vinyl monomers in the presence of lower levels of difunctional (di) vinyl monomers and chain transfer agents. In other processes, the use of controlled or living polymerization eliminates the need for chain transfer agents. In general, gelation can be avoided if the vinyl polymer, which is predominantly made from monofunctional monomers, is branched by means of difunctional vinyl monomers so that there is on average one branch or less per vinyl polymer chain, as described, for example, in WO 2009/122220, WO 2014/199174 and WO 2014199175.
Further examples of soluble branched polymers are disclosed in T.Sato, H.Ihara, T.Hirano, M.Seno, Polymer 2004,45, 7491-7498. This uses a high concentration of initiator and copolymerizes a divinyl monomer (ethylene glycol dimethacrylate-EGDMA) with a monovinyl monomer (N-methylmethacrylamide).
Another method of controlling branching is described in t.zhao, y.zheng, j.poly, w.wang, NatureCommunications 2013,10.1038/ncomm2887 and y.zheng, h.cao, b.newland, y.dong, a.pandit, w.wang; J.am.chem.Soc.2011,133, 13130-13137. This uses a deactivation-enhancing atom transfer radical polymerization (DE-ATRP). The oligomers made from divinyl monomers react with each other while they still have a small chain length, thereby avoiding intramolecular cyclization that can occur with longer living chains. Although this allows the formation of hyperbranched polymers, this process has some drawbacks. A metal catalyst system and a large amount of initiator are required. Most of the vinyl functionality remains in the final product. The polymerization must be terminated at low vinyl conversion to prevent gelation. Stringent purification of the final material is required.
T.sato, y.arima, m.seno, t.hirano; the homopolymerization of divinyl monomers using a large number of initiators is disclosed in Macromolecules 2005,38, 1627-. Although this results in soluble hyperbranched polymers, the functionality of the polymer is largely dependent on the large amount of initiator introduced. In addition, double bonds remain in the product. The polymerization process must be terminated at low vinyl conversion to prevent gelation.
Disclosure of Invention
We have now developed a new synthetic method which allows the preparation of materials similar to those conventionally prepared by step-growth polymerisation.
According to a first aspect, the present invention provides a process for preparing a polymer comprising forming carbon-carbon backbone segments (segments) of the polymer using free radical vinyl polymerisation, wherein the longest chains in the polymer comprise vinyl polymer chains that are interrupted with other chemical groups and/or chains.
Such polymers generally fall into the class of materials conventionally prepared by step-growth polymerization, for example, polyesters, polyamides, polyalkylphenylenes (or other phenyl-or aryl-containing polymers such as polyphenylene ether polymers), or polycarbonates. Thus, although not made by a step-growth process in the present invention, such polymers are generally referred to herein as and have the characteristics of step-growth polymers.
In other words, the present invention provides for the use of free radical polymerization to prepare a portion of a step-growth polymer or a portion of a polymer similar to polymers conventionally prepared by step-growth polymerization. The present invention constructs a segment of monomer residues in the resulting step-growth polymer.
We believe that this is the first time that conventional free radical polymerization processes are used in this manner. Free radical polymerization reactions are fast, clean and allow for functional groups that may be incompatible with step growth conditions.
The use of free radical polymerization enables a process to be obtained that is easy to control, does not require metal catalysis, and is extremely useful commercially and industrially.
Divinyl monomers (DVM) may be free radically polymerized in the present invention.
Thus, the chemical groups and/or chains interposed between the vinyl polymer chains of the product are those between the two double bonds of the divinyl monomer.
The monomers to be subjected to radical polymerization in the present invention need not have only two double bonds, but may have more double bonds. In other words, polyvinyl monomers (MVM) can be used, including both divinyl monomers and monomers having more than two vinyl groups, such as trivinyl monomers (TVM).
Thus, the polyvinyl monomer (MVM) can be free radically polymerized in the present invention.
Another way of understanding the present invention is believed to provide a method of preparing a polymer comprising forming a carbon-carbon segment of step-growth monomer residues using free radical vinyl polymerization. The term "step-growth monomer residue" is understood by the skilled polymer chemist as the structure that results within the polymer as a result of the introduction of monomers conventionally used in step-growth polymerisation.
The present invention therefore introduces a conceptually new type of polymerization, which is a hybrid (hybrid ) of two different types of polymerization, namely step-growth polymerization and chain-growth polymerization (especially radical vinyl polymerization). This may be referred to as "free radical step growth polymerization".
The type of step-growth monomer residue formed by vinyl polymerization will depend on the chemical functionality between the double bonds of the divinyl or polyvinyl monomers.
Several examples of how divinyl monomers can be used in practice are as follows.
In the case of polyesters, the carbon-carbon chain which the vinyl polymerization can form will conventionally correspond to A2+B2The carbon-carbon chain within the diol monomer or diacid monomer in the step-growth polymerization. The chain between the two double bonds of the divinyl monomer corresponds to the chain of complementary diacid or diol monomers that will be used. It should be noted that a range of different vinyl chain lengths will result from the use of free radical polymerization. This therefore opens up new routes for the preparation of new types of polyesters, similar to the step-growth polymerization using mixtures of different diols or mixtures of different diacids in the starting monomer raw materials.
In the case of polyamides, the carbon-carbon chain which the vinyl polymerization can form will conventionally correspond to A2+B2The carbon-carbon chain within the diamine (or equivalent) monomer or the diacid (or equivalent) monomer in the step-growth polymerization. The chain in the divinyl monomer (i.e., between its two double bonds) corresponds to the chain of the complementary diacid or diamine monomer to be used. Andpolyesters, like, produce a range of different vinyl chain lengths due to the use of free radical polymerization. This therefore opens up new preparation routes for new types of polyamides, similar to step-growth polymerization using different diamine mixtures or different diacid mixtures in the starting monomer raw materials.
Polyalkylphenylenes may be prepared using divinyl monomers containing a phenyl or aromatic group (and optionally other groups) between the two vinyl groups of the divinyl monomer. The vinyl group polymerizes to form a carbon-carbon chain linking the phenyl/aryl containing moiety.
Polycarbonates may be prepared using divinyl monomers containing one or more carbonates (and optionally other groups) between the two double bonds of the divinyl monomer. The vinyl group polymerizes to form a carbon-carbon chain connecting the carbonate-containing moieties.
Other variations of polyesters, polyamides, polyalkylphenylenes, and polycarbonates can be prepared using polyvinyl monomers instead of or in addition to divinyl monomers. This offers many possibilities for variations in structure, branch range, attributes and applications.
The types of polymers that can be prepared by the process of the present invention are not limited to those outlined above; indeed, the present invention is extremely useful in allowing the preparation of many other types of polymers. The monomer must contain a free radically polymerizable vinyl group, but may contain many other types of chemical moieties in addition thereto, which may then become the primary functional group (e.g., ester group, amide group, carbonate group, phenyl group, etc.) in the resulting polymer. In addition, more than one type of divinyl monomer and/or more than one type of multivinyl monomer may be used, allowing the preparation of new hybrid structures.
In some cases, the group in the monomer that becomes the predominant functional group in the polymer may be adjacent to or bonded to a vinyl group, for example, a polyester may be prepared using a diacrylate, dimethacrylate, or divinyl diester, or a polyamide may be prepared using a bisacrylamide,Dimethylacrylamide or divinyldiamide. In these six examples, the two ends of the divinyl monomer were each terminated as follows: -OC (═ O) -CH ═ CH2、-OC(＝O)-C(Me)＝CH2、-C(＝O)-O-CH＝CH2、-NH-C(＝O)-CH＝CH2、-NH-C(＝O)-C(Me)＝CH2、-C(＝O)-NH-CH＝CH2. In a similar example, the terminal ends of the polyvinyl monomers (e.g., the terminal ends of the trivinyl monomers) can terminate in the same moiety, and the trivinyl monomers can be, for example, a triacrylate, trimethacrylate, trivinyl triester, triacrylate, trimethacrylamide, or trivinyl triamide.
Alternatively, the group which becomes the predominant functional group in the polymer may not be adjacent to a vinyl group, for example, rather than comprising a-C (═ O) -O-group as part of an acrylate or methacrylate moiety, the divinyl monomer or polyvinyl monomer may contain one or more ester groups which are not directly bonded to both or either vinyl groups. Similarly, the amide group may or may not be directly bonded to the vinyl group. The same applies to carbonates, phenyl and other moieties.
The positions occupied by the groups which become the main functional groups may be present in mixture. For example, monomers having one or more groups adjacent to or bonded to a vinyl group and one or more groups not adjacent to or bonded to a vinyl group can be used.
Conveniently, with respect to the divinyl monomer, a vinyl group may be present at the end of the divinyl monomer such that a functional group of the divinyl monomer is between two vinyl groups or attached to a linkage between two vinyl groups. Similarly, in the trivinyl and higher vinyl monomers, the vinyl group or some of the vinyl groups may be terminal.
The invention is particularly useful for preparing branched polymers. Wherein branching occurs in the vinyl polymer chain. A structure is formed which was hitherto impossible to obtain.
We have found that a process for preparing a branched polymer according to the present invention may comprise: free radical polymerization of polyvinyl monomers is carried out using a source of radicals in the presence of a chain transfer agent (a source of radials), wherein the degree of propagation is controlled relative to the degree of chain transfer, thereby preventing gelation of the polymer.
The term polyvinyl monomer refers to a monomer having more than one free radically polymerizable vinyl group. One particular type of such monomer is a monomer having two such vinyl groups, i.e., a divinyl monomer.
Thus, the process for preparing a branched polymer according to the present invention may comprise: free radical polymerization of divinyl monomers is carried out using a free radical source in the presence of a chain transfer agent, wherein the degree of propagation is controlled relative to the degree of chain transfer, thereby preventing gelation of the polymer.
Thus, in contrast to some prior art processes, crosslinking and insolubility are not avoided by using a combination of a major amount of monovinyl monomer and a minor amount of divinyl monomer, but rather by controlling the manner in which divinyl monomer or other polyvinyl monomers react.
The polymer contains multiple vinyl polymer segments, and controlling the amount or rate of chain transfer relative to the amount or rate of propagation affects the average length of those vinyl polymer chains.
Thus, a method of making a branched polymer may comprise: free radical polymerization of a divinyl monomer is carried out using a free radical source in the presence of a chain transfer agent, wherein propagation is controlled with respect to chain transfer to yield a polymer having a plurality of vinyl polymer segments, wherein the average number of divinyl monomer residues per vinyl polymer chain is between 1 and 3.
The method of making a branched polymer may comprise: free radical polymerization of a plurality of vinyl monomers is carried out using a free radical source in the presence of a chain transfer agent, wherein propagation is controlled with respect to chain transfer to provide a polymer having a plurality of vinyl polymer segments, the average number of polyvinyl monomer residues per vinyl polymer chain being from 1 to 3.
The method of making a branched polymer may comprise: free radical polymerization of a trivinyl monomer is carried out using a free radical source in the presence of a chain transfer agent, wherein propagation is controlled with respect to chain transfer to provide a polymer having a plurality of vinyl polymer segments, wherein the average number of trivinyl monomer residues per vinyl polymer chain is from 1 to 2.
The method of making a branched polymer may comprise: free radical polymerization of a tetravinyl monomer is carried out using a free radical source in the presence of a chain transfer agent, wherein propagation is controlled with respect to chain transfer to provide a polymer having a plurality of vinyl polymer segments, wherein the average number of tetravinyl monomer residues per vinyl polymer chain is from 1 to 1.7.
Any suitable free radical source may be used for free radical polymerization. This may be, for example, an initiator such as AIBN. The free radicals may be provided thermally or photochemically or by other means.
Compared to some prior art processes, no large amounts of initiator are required; only a small amount of a free radical source is needed to initiate the reaction.
The person skilled in the art is able to control the chain transfer reaction with respect to the propagation reaction by known techniques. This can be done by using a sufficiently large amount of Chain Transfer Agent (CTA). Chain transfer agents end-cap (cap) the vinyl polymer chain, thereby limiting its length. It also controls chain end chemistry. Various chain transfer agents are suitable and are low cost and impart versatility to the process and resulting product.
The backbone (primary chains) is kept very short, thereby avoiding gel formation while achieving a high level of branching.
An important advantage of the present invention is the use of industrial free radical polymerization. This is completely scalable, very straightforward and very cost-effective. In contrast, some prior art processes are based on controlled or living polymerization and/or require the use of initiator systems or more complex purification schemes, or the use of step-growth polymerization processes having the above-mentioned disadvantages.
Alternatively, the only reagents used in the process of the present invention are one or more polyvinyl monomers (e.g., divinyl monomers), chain transfer agents, free radical sources, and optionally solvents. Thus, in contrast to some prior art processes, the present invention allows for the homopolymerization of polyvinyl monomers.
No monovinyl monomer is required in the process of the present invention.
However, a monovinyl monomer may optionally be used, i.e. copolymerization may optionally be carried out. For example, the process may include introducing not only a divinyl monomer, but also an amount, optionally a lesser amount, of a monovinyl monomer. For example, the molar amount of divinyl monomer relative to monovinyl monomer may be greater than 50%, greater than 75%, greater than 90%, or greater than 95%. Alternatively, the ratio of divinyl monomer residues to monovinyl monomer residues may be greater than or equal to 1:1, or greater than or equal to 3:1, greater than or equal to 10:1, or greater than or equal to 20: 1.
Alternatively, in some cases, more monovinyl monomer may be used. Alternatively, the method can include introducing not only one or more divinyl monomers but also monovinyl monomers, wherein, for example, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the vinyl monomers used are divinyl monomers. Alternatively, the method can include introducing not only one or more divinyl monomers but also monovinyl monomers, wherein, for example, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the vinyl monomer residues in the product are divinyl monomer residues.
The possible incorporation of monovinyl monomers applies not only to divinyl monomers but also to other types of polyvinyl monomers. Thus, the method can include introducing not only one or more polyvinyl monomers, but also monovinyl monomers, wherein, for example, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the vinyl monomers used are polyvinyl monomers. Alternatively, the method may comprise introducing not only one or more polyvinyl monomers but also monovinyl monomers, wherein in the product, for example, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the vinyl monomer residues are polyvinyl monomer residues.
Divinyl monomers
One type of polyvinyl monomer that can be used in the present invention is a divinyl monomer.
Divinyl monomers contain two double bonds, each of which is suitable for free radical polymerization. It may contain one or more other groups, for example, these other groups may be selected from, but are not limited to: an aliphatic chain; an ester group; an amide group; an ester group; a carbamate group; a silicone group; an amine group; an aromatic group; an oligomer or polymer; or a combination of one or more of these; and/or it may be optionally substituted. For example, there may be a PEG group or PDMS group between the double bonds, or a benzene ring (e.g., as in the monomer divinylbenzene) or other aromatic group.
For example, each vinyl group in the divinyl monomer may be an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group, a vinyl ester group, a vinyl aliphatic group, or a vinyl aromatic (e.g., styrene) group.
Due to the large amount of chain transfer agent in the reaction, the vinyl polymer chains in the final product are usually short and the chemistry of the longest chain in the polymer is governed by the other chemicals in the monomer. Thus, for example, monomers that contain ester linkages in addition to two vinyl groups (e.g., dimethacrylates such as EGDMA) polymerize to form a polyester structure in which the longest repeating unit contains an ester. Similarly, monomers containing amide linkages in addition to two vinyl groups (e.g., bisacrylamide) polymerize to form a polyamide structure in which the longest repeating unit comprises an amide.
The present invention therefore opens up new processes for the preparation of polyesters, polyamides or other polymers, allowing the formation of structural types different from those previously thought possible.
The divinyl monomer may be stimuli responsive, for example, may be pH, thermally or biologically responsive. The response may be degradation. For example, the linkage between two double bonds may be acid-cleavable or base-cleavable, e.g., may comprise an acetal group. This allows the preparation of commercial products which are stimulus-responsive branched polymers. Alternatively, the method of the invention may comprise the further steps of: the divinyl monomer is cleaved to remove bridges in the polymer, such that the commercial product is one in which the linkages between the vinyl polymer chains have been removed or reduced.
Alternatively, a mixture of divinyl monomers may be used. Thus, two or more different divinyl monomers may be copolymerized.
Other types of polyvinyl monomers
Polyvinyl monomers other than divinyl monomers may be used, for example, trivinyl monomers, tetravinyl monomers, and/or monomers having more vinyl groups. In particular, trivinyl monomers are useful because they can be obtained or prepared with less difficulty and allow further selection to produce different types of branched polymers. The discussion, disclosure and teachings herein with respect to divinyl monomers apply mutatis mutandis to other polyvinyl monomers as well.
Chain Transfer Agent (CTA)
Any suitable chain transfer agent may be used.
These include mercaptans, including optionally substituted aliphatic mercaptans such as dodecyl mercaptan (DDT). Another suitable chain transfer agent is alpha-methylstyrene dimer. The other is 2-isopropoxyethanol. Other compounds having functional groups known to allow free radical chain transfer may be used. These can be tailored to bring the desired functionality to the polymer.
Chain end chemistry can be tailored by the choice of CTA. Thus, hydrophobic/hydrophilic behavior and other properties can be influenced. For example, an alkyl thiol may have properties that are completely different from alcohol-containing groups, acid-containing groups, or amine-containing groups.
Alternatively, a mixture of CTAs may be used. Thus, two or more different CTAs can be introduced into the product.
Relative amounts of chain transfer agent and divinyl monomer
The relative amounts of chain transfer agent and divinyl monomer can be readily varied and optimized by conventional methods to obtain non-gelled polymers without undue burden to those skilled in the art. The analysis of the product can be carried out by conventional procedures, for example, the relative amounts of chain transfer agent and divinyl monomer can be determined by NMR analysis.
With respect to the reagents used, at least 1 equivalent, or 1 to 10 equivalents, or 1.2 to 10 equivalents, or 1.3 to 5 equivalents, or 1 to 3 equivalents, or 1 to 2 equivalents, or 1.2 to 3 equivalents, or 1.2 to 2 equivalents of chain transfer agent may optionally be used relative to the divinyl monomer. The presence of a large amount of chain transfer agent means that: on average, vinyl polymer backbones are shorter when reacted and end capped with chain transfer agents. This procedure corresponds to telomerization (telmerization), i.e.the formation of short chains with a smaller number of repeating units.
In the final product, there may be n +1 chain transfer agent moieties per n divinyl monomer moieties (thus tending to a 1:1 ratio as molecular weight increases): this is based on the situation in which macromolecules of a theoretically ideal limited size are formed. However, other situations are also possible, for example, intramolecular ring reactions can take place or initiators can be introduced: thus, ratios other than (n +1): n are actually possible. Alternatively, there may be an average of from 0.5 to 2, alternatively from 0.7 to 1.5, alternatively from 0.75 to 1.3, alternatively from 0.8 to 1.2, alternatively from 0.9 to 1.1, alternatively from 1 to 1.05, alternatively about 1 chain transfer agent moiety per divinyl monomer moiety.
Without wishing to be bound by theory, this ideal case of (n +1): n relationship can be rationalized as follows. There may be one chain transfer agent per vinyl polymer chain (e.g., if the chain transfer agent is a mercaptan ("RSH"), an RS-radical is introduced at one end of the chain and an H-radical is introduced at the other end). The simplest theoretical product comprises a single divinyl monomer in which both double bonds are each capped with a chain transfer agent (so that both double bonds can each be considered to be vinyl polymer chains of only one vinyl length). Thus, in this simplest theoretical product, there is 1 more chain transfer agent than divinyl monomer (2 to 1). For each additional growth (i.e. for each additional divinyl monomer introduced), if a product of limited size is to be obtained and if no intramolecular cross-linking is to be carried out, it is necessary to introduce a further chain transfer agent: this is because one double bond of the further divinyl monomer may be introduced into an existing chain without the need for a further chain transfer agent, while the other double bond of the further divinyl monomer requires a further chain transfer agent to end-cap it.
Thus, according to this theoretical evaluation, some examples of the ratio of Chain Transfer Agent (CTA) residues to divinyl monomer (DVM) residues in the product are as follows:
it can be seen that the ratio of CTA to DVM tends to 1 as the molecular weight increases.
Relative amounts of chain transfer agent and trivinyl monomer
When the polyvinyl monomer used is a trivinyl monomer, the following may be optionally applied.
With respect to the reagents used, at least 2 equivalents, or 2 to 20 equivalents, or 2.4 to 20 equivalents, or 2.6 to 10 equivalents, or 2 to 6 equivalents, or 2 to 4 equivalents, or 2.4 to 6 equivalents, or 2.4 to 4 equivalents of chain transfer agent may optionally be used relative to the trivinyl monomer.
In the final product, there may be 2n +1 chain transfer agent moieties per n trivinyl monomer moieties (thus, as the molecular weight increases, a ratio of 2:1 tends to be): this is based on the situation in which ideal macromolecules of theoretically limited size are formed. However, other situations are also possible, for example, intramolecular ring reactions can take place or initiators can be introduced: thus, in practice other ratios than (2n +1): n are possible. Alternatively, there are an average of 1 to 4, alternatively 1.4 to 3, alternatively 1.5 to 2.6, or 1.6 to 2.4, or 1.8 to 2.2, or 2 to 2.1, or about 2 chain transfer agent moieties per trivinyl monomer moiety.
Without wishing to be bound by theory, this idealized (2n +1): n relationship can be rationalized as follows. There may be a chain transfer agent per vinyl polymer chain (e.g., if the chain transfer agent is a mercaptan ("RSH"), an RS-radical is introduced at one end of the chain and an H-radical is introduced at the other end). The simplest theoretical product comprises a single trivinyl monomer in which each of the three double bonds is capped with a chain transfer agent (so that each of the three double bonds can be considered as a vinyl polymer chain of only one vinyl length). Thus, in this simplest theoretical product, there are 2 more chain transfer agents than trivinyl monomers (3 to 1). For each additional growth (i.e. for each additional trivinyl monomer introduced), if a product of limited size is to be obtained and if no intramolecular cross-linking is to be carried out, it is necessary to introduce two further chain transfer agents: this is because one double bond of the additional trivinyl monomer can be introduced into an existing chain without the need for further chain transfer agents, while the other two double bonds of the additional trivinyl monomer require further chain transfer agents to cap it.
Thus, according to this theoretical evaluation, some examples of the ratio of chain transfer agent residues to trivinyl monomer (TVM) residues in the product are as follows:
it can be seen that the ratio of CTA to trivinyl monomer tends to 2 as the molecular weight increases.
Relative amounts of chain transfer agent and tetravinyl monomer
When the polyvinyl monomer used is a tetravinyl monomer, the following may be optionally applied.
With respect to the reagents used, at least 3 equivalents, or 3 to 30 equivalents, or 3.6 to 30 equivalents, or 3.9 to 15 equivalents, or 3 to 9 equivalents, or 3 to 6 equivalents, or 3.6 to 9 equivalents, or 3.6 to 6 equivalents of chain transfer agent may optionally be used with respect to the tetravinyl monomer.
In the final product, there may be 3n +1 chain transfer agent moieties per n trivinyl monomer moieties (thus, as the molecular weight increases, a ratio of 3:1 tends to be): this is based on the situation in which ideal macromolecules of theoretically limited size are formed. However, other situations are also possible, for example, intramolecular ring reactions can take place or initiators can be introduced: thus, in practice other ratios than (3n +1): n are possible. Alternatively, there may be an average of from 1.5 to 6, alternatively from 2.1 to 4.5, alternatively from 2.25 to 3.9, alternatively from 2.4 to 3.6, alternatively from 2.7 to 3.3, alternatively from 3 to 3.15, or about 3 chain transfer agent moieties per tetravinyl monomer moiety.
Without wishing to be bound by theory, this idealized (3n +1): n relationship can be rationalized as follows. There may be a chain transfer agent per vinyl polymer chain (e.g., if the chain transfer agent is a mercaptan ("RSH"), an RS-radical is introduced at one end of the chain and an H-radical is introduced at the other end). The simplest theoretical product comprises a single tetravinyl monomer in which each of the four double bonds is capped with a chain transfer agent (so that each of the four double bonds can be considered as a vinyl polymer chain of only one vinyl length). Thus, in this simplest theoretical product, there are 3 more chain transfer agents than trivinyl monomers (4 to 1). For each additional growth (i.e. for each additional tetraethylene-based monomer introduced), if a product of limited size is to be obtained and if no intramolecular cross-linking is to be carried out, then a further introduction of three chain transfer agents is required: this is because one double bond of the further tetravinyl monomer can be introduced into an existing chain which does not require further chain transfer agents, while the other three double bonds of the further tetravinyl monomer require further chain transfer agents to cap it.
Thus, according to this theoretical evaluation, some examples of the ratio of chain transfer agent residue to tetravinyl monomer residue in the product are as follows:
it can be seen that the ratio of CTA to tetravinyl monomer tends to 3 as the molecular weight increases.
Relative amounts of chain transfer agent and polyvinyl monomer
The numerical relationship and theoretical evaluation of each of the divinyl monomer, the trivinyl monomer, and the tetravinyl monomer have been shown above.
In summary, without wishing to be bound by theory, in certain ideal cases, the number of CTA residues per n MVM residues in the final product may be as follows:
thus, it can be seen that as the valence (valency) of the monomer increases, more and more CTA is required to end-cap the chain in the final product unless some other mechanism (e.g., intramolecular reaction) does so.
In general, the following may optionally be applied to the various types of polyvinyl monomers discussed herein. With respect to the reagents used, at least 1 equivalent, or 1 to 30 equivalents, or 1.2 to 30 equivalents, or 1.3 to 15 equivalents, or 1 to 9 equivalents, or 1 to 6 equivalents, or 1.2 to 9 equivalents, or 1.2 to 6 equivalents of chain transfer agent may optionally be used with respect to the tetravinyl monomer. In the final product, there may optionally be an average of 0.5 to 6, optionally 0.7 to 4.5, optionally 0.75 to 3.9, or 0.8 to 3.6, or 0.9 to 3.3, or 1 to 3.15, or about 1 to about 3 chain transfer agent moieties per polyvinyl monomer moiety.
Degree of vinyl polymerization
It is believed that an important feature of the process of the present invention is the relatively short average length of the vinyl polymer chains throughout the polymer. A typical polymer molecule prepared according to the present invention will comprise a number of vinyl polymer chains (each on average shorter) linked together by moieties between double bonds in the polyvinyl monomer.
This can be achieved by adjusting the conditions, including adjusting the amount of chain transfer agent, such that the chain transfer rate matches the vinyl polymerization rate to a desired extent. The type (identity ) of the polyvinyl monomer and chain transfer agent, as well as other factors, affect this balance, but the progress of the reaction can be readily monitored and the properties of the resulting polymer readily determined by known conventional techniques. Thus, there is no unnecessary burden on those skilled in the art in carrying out the method according to the present invention or in determining which methods fall within the scope of the present invention. In this case, the resulting chain length is the kinetic chain length.
Degree of vinyl polymerization Using divinyl monomer
The number of propagation steps (i.e., how many divinyl monomers to add) before each chain transfer (i.e., termination of propagation of vinyl polymer chains) needs to be high enough to produce a branched polymer, yet low enough to prevent gelation. This appears to be a suitable vinyl polymer having an average chain length of 1 to 3,1 to 2.5, 1 to 2.2, 1 to 2, 1.3 to 2, 1.5 to 2, 1.7 to 2, 1.8 to 2, 1.9 to 2, or 1.95 to 2, or about 2 divinyl monomer residues.
Although the average value may alternatively be 1-3, a small number of vinyl polymer chains may contain significantly more divinyl monomer residues, for example, up to 10, 15, 18, 20 or more.
Alternatively, 90% of the vinyl polymer chains comprise less than 10 DVM residues, or 90% have a length of 7 or less, or 90% have a length of 5 or less, or 95% have a length of 15 or less, or 95% have a length of 10 or less, or 95% have a length of 7 or less, or 75% have a length of 10 or less, or 75% have a length of 7 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less.
Without wishing to be bound by theory, the average vinyl polymer chain length or kinetic chain length can be calculated as follows, assuming no intramolecular reactions are present. As discussed above, if there are n +1 chain transfer agent moieties per n divinyl monomer moieties and one chain transfer agent per vinyl polymer chain, then, since there are 2n double bonds per n divinyl monomers, the number of double bond residues per chain will average to 2n/(n +1), which tends to be 2 as the molecular weight increases.
Thus, according to this theoretical evaluation, some examples of average vinyl chain lengths are as follows:
it can be seen that under certain theoretical conditions the average kinetic chain length ranges from 1 to 2. In practice, the value may not be within this range: other reactions may occur, for example, intramolecular polymerization.
It will be appreciated by those skilled in the art that, depending on the conditions, the process can produce a range of products, which can include low molecular weight products (the smallest being products containing only one DVM, i.e. where the vinyl chain length is 1) to high molecular weight products. Whether and how the product mixture is purified will of course affect the composition of the product and thus the length of the vinyl polymer chains present. Thus, in some cases, the average vinyl polymer chain length in the resulting purified product can be higher with the removal of lower molecular weight products.
Empirically, a suitable degree of polymerization is determined by the following steps: 1) using representative monofunctional monomers that are chemically similar to the polyfunctional monomers, 2) using the CTA of interest, 3) performing a series of linear polymerizations at different CTA/monomer ratios, 4) analyzing the product and 5) determining the average chain length.
We use DVMs that contain a cleavable group between two vinyl groups. These not only allow the preparation of interesting and commercially useful products, but also allow the investigation of the extent of vinyl polymerization.
As shown in the examples below, we have performed polymerization with degradable DVM and then subject the product to conditions under which the DVM decomposes. This breaks the connecting bridges within the branched vinyl polymer, resulting in a series of linear vinyl chains. Analysis of these shows the distribution of vinyl polymer chain lengths formed by the process of the present invention. Interestingly, the reaction of similar monovinyl monomers gives very similar chain length distributions. This supports the theoretical analysis outlined above, indicating that the process can be tailored, and indirectly that polymerization can proceed efficiently whether the DVM is homopolymerized or polymerized with some monovinyl monomer present.
Alternatively, the product may comprise a plurality of divinyl monomer residues with one of the double bond residues being terminated by a chain transfer agent (as opposed to being part of the chain), i.e. having a nominal chain length (nominal chain length) of 1. The other double bond residues of these divinyl monomer residues may be part of the longer chain. This may be the most common form of vinyl residue in the product. Alternatively, the most common vinyl "chain" is a chain that contains only one residue of a divinyl monomer. Alternatively, the two most common vinyl chains are (i) a vinyl "chain" comprising only one divinyl monomer residue and (ii) a vinyl chain comprising an integer number of divinyl monomer residues selected from 2 to 8, such as 2 to 7, such as 2 to 6, such as 3 to 8, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 4 or 5, such as 5. Alternatively, the most common vinyl "chain" is a chain comprising only one residue of a divinyl monomer, while the second most common vinyl chain comprises an integer number of residues of a divinyl monomer selected from 2 to 8, such as 2 to 7, such as 2 to 6, such as 3 to 8, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 4 or 5, such as 5. Alternatively, the distribution of chain lengths may be bimodal, for example, the peak may occur at a second chain length of 1 and may alternatively be 3 to 8, for example 3 to 7, for example 3 to 6, for example 3 to 5, for example 4 or 5, for example 5.
Extent of vinyl polymerization Using trivinyl monomers
The number of propagation steps (i.e., how many trivinyl monomers are added) before each chain transfer (i.e., termination of propagation of the vinyl polymer chain) needs to be high enough to produce branched polymer, yet low enough to prevent gelation. This appears to be a suitable vinyl polymer having an average chain length of from 1 to 2, 1 to 1.8, 1 to 1.7, 1 to 1.5, 1.1 to 1.5, 1.2 to 1.5, 1.25 to 1.5, 1.3 to 1.5, 1.4 to 1.5, or 1.45 to 1.5, or about 1.5 divinyl monomer residues.
Although the average value may alternatively be 1-2, a small number of vinyl polymer chains may contain significantly more trivinyl monomer residues, for example, up to 5, 10, 15, 18, 20, or more.
Alternatively, 90% of the vinyl polymer chains comprise less than 8 TVM residues, or 90% have a length of 5 or less, or 90% have a length of 4 or less, or 95% have a length of 10 or less, or 95% have a length of 8 or less, or 95% have a length of 5 or less, or 75% have a length of 8 or less, or 75% have a length of 6 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less.
Without wishing to be bound by theory, the average vinyl polymer chain length or kinetic chain length can be calculated as follows, assuming no intramolecular reactions are present. As discussed above, if there are 2n +1 chain transfer agent moieties per n trivinyl monomer moieties and one chain transfer agent per vinyl polymer chain, then since there are 3n double bonds per n trivinyl monomers, the number of double bond residues per chain will average to 3n/(2n +1), which tends to be 1.5 as the molecular weight increases.
Thus, according to this theoretical evaluation, some examples of average vinyl chain lengths are as follows:
it can be seen that under certain theoretical conditions the average kinetic chain length ranges from 1 to 1.5. In practice, the value may not be within this range: other reactions may occur, for example, intramolecular polymerization.
It will be understood by those skilled in the art that depending on the conditions, the process can produce a range of products, which can include low molecular weight products (minimally products containing only one TVM, i.e., products in which the vinyl chain length is 1) to high molecular weight products. Whether and how the product mixture is purified will of course affect the composition of the product and thus the length of the vinyl polymer chains present. Thus, in some cases, the average vinyl polymer chain length in the resulting purified product can be higher with the removal of lower molecular weight products.
Alternatively, the product may comprise a plurality of residues of trivinyl monomers in which two of the double bond residues are terminated by chain transfer agents (as opposed to being part of the chain), i.e., have a nominal chain length of 1. The other double bond residues of these trivinyl monomer residues may be part of the longer chain. This may be the most common form of vinyl residue in the product. Alternatively, the most common vinyl "chain" is a chain that contains only one residue of a trivinyl monomer. Alternatively, the two most common vinyl chains are (i) a vinyl "chain" comprising only one residue of a trivinyl monomer and (ii) a vinyl chain comprising an integer number of trivinyl monomer residues selected from 2 to 7, such as 2 to 6, such as 2 to 5, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 3 or 4, such as 4. Alternatively, the most common vinyl "chain" is a chain comprising only one residue of a trivinyl monomer, while the second most common vinyl chain comprises an integer number of trivinyl monomer residues selected from 2 to 7, such as 2 to 6, such as 2 to 5, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 3 or 4, such as 3 or such as 4. Alternatively, the distribution of chain lengths may be bimodal, for example the peak may occur at a chain length of 1 and may alternatively be 3 to 7, for example 3 to 6, for example 3 to 5, for example 3 or 4, at the second chain length.
Extent of vinyl polymerization Using tetravinyl monomers
The number of propagation steps (i.e., how many tetravinyl monomers are added) before each chain transfer (i.e., termination of propagation of the vinyl polymer chain) needs to be high enough to produce a branched polymer, yet low enough to prevent gelation. This appears to be a suitable vinyl polymer having an average chain length of from 1 to 1.7, 1 to 1.5, 1 to 1.4, 1 to 1.33, 1.1 to 1.33, 1.2 to 1.33, 1.25 to 1.33, or 1.3 to 1.33, or about 1.33 residues of tetravinyl monomers.
Although the average value may alternatively be 1-1.7, a minor amount of the vinyl polymer chains may comprise significantly more tetraethylene monomer residues, e.g., up to 3, 5, 10, 15, 18, 20, or more.
Alternatively, 90% of the vinyl polymer chains comprise less than 6 tetraethylene monomer residues, or 90% have a length of 4 or less, or 90% have a length of 3 or less, or 90% have a length of 2 or less, or 95% have a length of 8 or less, or 95% have a length of 6 or less, or 95% have a length of 4 or less, or 95% have a length of 3 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less.
Without wishing to be bound by theory, the average vinyl polymer chain length or kinetic chain length can be calculated as follows, assuming no intramolecular reactions are present. As discussed above, if there are 3n +1 chain transfer agent moieties per n tetravinyl monomer moieties and one chain transfer agent per vinyl polymer chain, then, since there are 4n double bonds per n tetravinyl monomers, the number of double bond residues per chain will average to 4n/(3n +1), which tends to be 1.33 as molecular weight increases.
Thus, according to this theoretical evaluation, some examples of average vinyl chain lengths are as follows:
it can be seen that under certain theoretical conditions the average kinetic chain length ranges from 1 to 1.33. In practice, the value may not be within this range: other reactions may occur, for example, intramolecular polymerization.
It will be appreciated by those skilled in the art that, depending on the conditions, the process can produce a range of products which can include low molecular weight products (minimally products comprising only one tetravinyl monomer, i.e. products in which the vinyl chain length is 1) to high molecular weight products. Whether and how the product mixture is purified will of course affect the composition of the product and thus the length of the vinyl polymer chains present. Thus, in some cases, the average vinyl polymer chain length in the resulting purified product can be higher with the removal of lower molecular weight products.
Alternatively, the product may comprise a plurality of tetravinyl monomer residues, wherein three of the double bond residues are capped (as opposed to being part of the chain) with a chain transfer agent, i.e., having a nominal chain length of 1. The other double bond residues of these tetravinyl monomer residues may be part of the longer chain. This may be the most common form of vinyl residue in the product. Alternatively, the most common vinyl "chain" is a chain comprising only one residue of a tetravinyl monomer. Alternatively, the two most common vinyl chains are (i) a vinyl "chain" comprising only one residue of a tetravinyl monomer and (ii) a vinyl chain comprising an integer number of tetravinyl monomer residues selected from 2 to 6, such as 2 to 5, such as 2 to 4, such as 3 to 6, such as 3 to 5, such as 3 or 4, such as 3 or such as 4. Alternatively, the most common vinyl "chain" is a chain comprising only one tetravinyl monomer residue, while the second most common vinyl chain comprises an integer number of tetravinyl monomer residues selected from 2 to 6, such as 2 to 5, such as 2 to 4, such as 3 to 6, such as 3 to 5, such as 3 or 4, such as 3 or such as 4. Alternatively, the distribution of chain lengths may be bimodal, for example, the peak may occur at a chain length of 1 and may alternatively be at a second chain length of 3 to 6, for example 3 to 5, for example 3 or 4, for example 3 or for example 4.
Generally the extent of vinyl polymerization when using polyvinyl monomers
The numerical relationship and theoretical evaluation of each of the divinyl monomer, the trivinyl monomer, and the tetravinyl monomer have been set forth above.
In summary, without wishing to be bound by theory, in certain desirable cases, the average number of multi-vinyl monomer residues per vinyl polymer chain may be as follows, wherein the product comprises n multi-vinyl monomer residues:
thus, it can be seen that as the valence order of the monomer increases, the average vinyl chain length is required to decrease.
Generally, the following may optionally be applied to each type of polyvinyl monomer discussed herein.
The average chain length of the vinyl polymer may comprise the following number of polyvinyl monomer residues: 1-3, 1-2.5, 1-2.2, 1-2, 1.1-2, 1.2-2, 1.3-2, 1.33-2, 1.5-2, 1.8-2, 1.9-2, 1.95-2, 1.2-1.5, 1.3-1.5, 1.4-1.5, 1.45-1.5, 1.1-1.4, 1.2-1.33 or 1.3-1.33.
Although the average value may alternatively be 1-3, a minor amount of vinyl polymer chains may contain significantly more polyvinyl monomer residues, for example, up to 3, 5, 8, 10, 15, 18, 20, or more.
Alternatively, 90% of the vinyl polymer chains comprise less than 10 residues of the multivinyl monomer, or 90% have a length of 7 or less, or 90% have a length of 5 or less, or 90% have a length of 4 or less, or 90% have a length of 3 or less, or 90% have a length of 2 or less, or 95% have a length of 15 or less, or 95% have a length of 10 or less, or 95% have a length of 7 or less, or 95% have a length of 5 or less, or 95% have a length of 4 or less, or 95% have a length of 3 or less, or 75% have a length of 10 or less, or 75% have a length of 7 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less.
Alternatively, the product may comprise a plurality of residues of polyvinyl monomer in which all but one of the double bond residues are terminated (as opposed to being part of the chain) by a chain transfer agent, i.e. having a nominal chain length of 1. The remaining double bond residues of these polyvinyl monomer residues may be part of the longer chain. This may be the most common form of vinyl residue in the product. Alternatively, the most common vinyl "chain" is a chain that contains only one residue of a polyvinyl monomer. Alternatively, the two most common vinyl chains are (i) a vinyl "chain" comprising only one residue of the multivinyl monomer and (ii) a vinyl chain comprising an integer number of residues of the multivinyl monomer selected from 2 to 8, such as 2 to 7, such as 2 to 6, such as 2 to 5, such as 3 to 8, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 3, such as 4, or such as 5. Alternatively, the most common vinyl "chain" is a chain comprising only one residue of a multivinyl monomer, while the second most common vinyl chain comprises an integer number of residues of the multivinyl monomer selected from 2 to 8, such as 2 to 7, such as 2 to 6, such as 2 to 5, such as 3 to 8, such as 3 to 7, such as 3 to 6, such as 3 to 5, such as 3, such as 4, or such as 5. Alternatively, the distribution of chain lengths may be bimodal, for example the peak may occur at a chain length of 1 and may alternatively be at a second chain length of 3 to 8, for example 3 to 7, for example 3 to 6, for example 3 to 5, for example 3, 4 or 5.
Free radical source
The free radical source may be an initiator, such as Azobisisobutyronitrile (AIBN). Alternatively, the amount may be 0.001 to 1, 0.01 to 0.1, 0.01 to 0.05, 0.02 to 0.04, or about 0.03 equivalents relative to the divinyl monomer. Considering the presence of two double bonds per monomer, this is equal to 0.0005-0.5, 0.005-0.05, 0.005-0.025, 0.01-0.02 or about 0.015 equivalents relative to the double bond.
It was found that the reaction proceeded efficiently when only a small amount of initiator was used. Reducing the amount of initiator means that the reaction can proceed more slowly, but still at an industrially acceptable rate. Lower amounts of initiator are beneficial in terms of cost, residual effects in the product, and controlling the exotherm to improve safety and promote reaction control even if scaled up.
Other possible sources of free radicals include peroxides, organoboranes, persulfates, or UV initiating systems.
Reaction conditions
The reaction can be carried out under conventional commercial free radical polymerization conditions. A solvent such as toluene may be optionally used.
As the reaction conditions become more dilute (e.g., as shown in the examples below, where the solids content is reduced from 50 wt% to 10 wt%), the amount of CTA in the product can be reduced. Without wishing to be bound by theory, this may be because at greater dilution intramolecular reactions are more likely to occur, meaning that the reaction of a molecule with itself effectively replaces the reaction of a molecule with a CTA molecule. Accordingly, this may alter the numerical relationships discussed above, as none of these assumptions are theoretical situations of intramolecular reactions.
This provides an additional way of controlling the chemistry and adjusting the type of product and its properties. For example, while in some cases it may be desirable to have a large number of CTA residues in the product, in other cases it may be desirable, for example, not to reduce the amount of thiol residues. Furthermore, performing the same reaction at different dilutions may result in different physical properties, e.g., making some products solid while others are liquid. The manner in which the glass transition temperature and/or melting temperature is adjusted may be suitable for various applications.
Conversion rate
According to the present invention, polymerization can be carried out to the extent that the polymer product contains very little, substantially no, or no residual vinyl functionality. Optionally, no more than 20 mol%, no more than 10 mol%, no more than 5 mol%, no more than 2 mol%, or no more than 1 mol% of free radically polymerizable double bonds of the divinyl monomer remain in the polymer. As shown below, NMR analysis has shown that the products of the invention can be obtained without measurable residual vinyl signals. This is clearly advantageous in controlling the chemistry and subsequent performance of the product.
In contrast, some prior art using ATRP or RAFT processes disclose that polymerization stops at lower conversion, e.g., such that more than 30% of the double bonds may remain. This is done in the prior art to prevent gelling.
By using large amounts of CTA and/or controlling other aspects of the reaction, the present invention not only avoids gelation, but also allows for substantially complete conversion.
The process of the invention is also advantageous in that the reaction can be completed in a short time. To our observation, on a laboratory scale, the reaction was essentially complete after approximately 2.5 hours: thereafter, the molecular weight distribution (determined by size exclusion chromatography) did not increase significantly. Even on an industrial scale, it is expected that the process will be completed within 8 hours, i.e. within one work shift. Under lean conditions, the process may take longer, but acceptable conversion may still be achieved over a reasonable period of time.
Alternatively and suitably in many embodiments, the polymer of the invention may be non-gelling. Alternatively, the present invention may be defined in terms of other characteristics described above (alone or in combination), such as chain length, amount of chain transfer agent, degree of conversion, and/or amount of initiator. For example, the present invention provides a method of making a branched polymer comprising: free radical polymerization of a divinyl monomer is carried out using a free radical source in the presence of a chain transfer agent, wherein 1 to 10 molar equivalents of chain transfer agent are used relative to the divinyl monomer, and/or wherein the polymer product comprises on average 0.9 to 1.1 chain transfer agent moieties per divinyl monomer moiety, and/or wherein the average vinyl polymer chain length is 1.8 to 2 divinyl monomer residues, and/or wherein the conversion of the divinyl monomer to the polymer is 80% or more, and/or wherein 0.001 to 1 molar equivalents of the free radical source are used relative to the divinyl monomer. In other examples, the present disclosure provides a method of making a branched polymer comprising: free radical polymerization of a polyvinyl monomer using a free radical source in the presence of a chain transfer agent, wherein 1 to 6 molar equivalents of chain transfer agent are used relative to the polyvinyl monomer, and/or wherein the polymer product comprises on average 1 to 3 chain transfer agent moieties per polyvinyl monomer moiety, and/or wherein the vinyl polymer has an average chain length of 1.33 to 2 polyvinyl monomer residues, and/or wherein the conversion of the polyvinyl monomer to polymer is 80% or more, and/or 0.001 to 1 molar equivalent of free radical source relative to the polyvinyl monomer.
Polymer product
The present invention relates not only to a novel polymerization process, but also to the corresponding polymerization products. This process imparts particularly different characteristics (in particular in terms of structure, branching and solubility).
Thus, according to a further aspect, the present invention provides a polymer obtainable by the process of the invention.
According to yet other aspects, the present invention provides a polymer obtainable by the process of the invention.
The products may also be defined structurally rather than as products that are characteristic of the process.
Thus, according to a further aspect, the present invention provides a branched polymer comprising vinyl polymer chains, wherein the vinyl polymer chains comprise the vinyl residues of a divinyl monomer, and wherein the longest chains in the polymer are not vinyl polymer chains but extend through linkages between double bonds of the divinyl monomer.
For example, the polymerization of divinyl monomer EGDMA generates its largest chain by combining a repeating branched polyester of mixed polyacid residues and ethylene glycol monomer residues.
The branched polymer product may optionally comprise divinyl monomer residues and chain transfer residues, wherein the molar ratio of chain transfer residues to divinyl monomer residues is from 0.5 to 2. The ratio is optionally from 0.7 to 1.5, optionally from 0.75 to 1.3, optionally from 0.8 to 1.2, optionally from 0.9 to 1.1, optionally from 1 to 1.05, optionally about 1.
Some vinyl polymer chains may contain up to 18 or 15 divinyl monomer residues. However, only a small proportion is so long: the average value of the high molecular weight material may be about 2.
Alternatively, 90% of the vinyl polymer chains comprise less than 10 DVM residues, or 90% have a length of 7 or less, or 90% have a length of 5 or less, or 95% have a length of 15 or less, or 95% have a length of 10 or less, or 95% have a length of 7 or less, or 75% have a length of 10 or less, or 75% have a length of 7 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less.
During the reaction, both carbon atoms of the vinyl group may not be bonded to another vinyl group (instead, they may be bonded to a CTA residue or hydrogen or in some cases to other moieties such as an initiator residue or a solvent residue), or one of the two carbon atoms of the vinyl group may be bonded to another vinyl group, or both carbon atoms of the vinyl group may be bonded to other vinyl groups. Thus, in the product, each vinyl residue may be directly attached to 0, 1 or 2 other vinyl residues as the closest group. We have found that when the average value of the number is within a specified range, an effective branched polymer is obtained. The branched polymer product may optionally comprise divinyl monomer residues and chain transfer residues, wherein each vinyl residue is directly polymerized by a vinyl group to an average of 0.5 to 1.5 other divinyl monomer residues. Alternatively, this may average 0.8-1.2, 0.8-1.1, or 0.9-1.
Thus, the polymers of the present invention are characterized by having a high amount of chain transfer agent incorporation, and also by having short unique vinyl polymer chains. Conventionally, vinyl polymer chains will generally comprise a long saturated backbone, however in the present invention-although the polymer is built using vinyl polymerization-most of the double bonds react with only one other double bond, or not with other double bonds, rather than with the other two double bonds. This means that: the connecting bond between two double bonds in the monomers usually causes branching between the polymer chains in the prior art, whereas in the present invention the longest polymer chain main chain is formed. This is conceptually different from the prior art and represents a step change in how branched polymerization can be achieved.
As mentioned above, other ways of defining the invention are based on the limited length of the vinyl segments within the polymer.
The branched polymer product optionally comprises divinyl monomer residues and chain transfer residues, wherein the branched polymer product comprises a plurality of vinyl polymer segments having an average length of 1 to 3 divinyl monomer residues.
The average length can be 1-2.5, 1-2.2, 1-2, 1.3-2, 1.5-2, 1.7-2, 1.8-2, 1.9-2, 1.95-2, or about 2.
One skilled in the art will understand how the number of double bond residues affects the carbon chain length of the resulting vinyl polymer segment. For example, in the case where the polymer segment contains 2 double bond residues, this corresponds to a saturated carbon segment of 4 carbon atoms.
The introduction of a monovinyl monomer as well as a divinyl monomer can affect the average vinyl chain length but not the average number of divinyl monomer residues per chain. It may be one way to add vinyl chains without adding branching.
The product may also be defined in terms of the amount of residual vinyl functionality.
The branched polymer product optionally comprises divinyl monomer residues and chain transfer residues, wherein the divinyl monomer residues comprise less than 20 mole% double bond functionality.
In other words, in this polymer product, at least 80% of the double bonds of the divinyl monomer have reacted to form saturated carbon-carbon chains.
The residue may comprise less than 10 mol%, or less than 5 mol%, or less than 2 mol%, or less than 1 mol%, or substantially no double bond functionality.
Another way to define the product is according to its Mark Houwink α value. Alternatively, the value may be lower than 0.5.
The above description of the polymer product specifically relates to those comprising divinyl monomer residues. Similarly, the present invention provides polymer products containing other multi-vinyl monomer residues, for example, including tri-vinyl monomer residues and tetra-vinyl monomer residues. The disclosure herein regarding the polymerization process also applies to the resulting product.
Thus, the branched polymer product may optionally comprise polyvinyl monomer residues and chain transfer residues, wherein the average molar ratio of chain transfer residues to polyvinyl monomer residues may optionally be:
generally for polyvinyl monomers:
0.5-6, 0.7-4.5, 0.75-3.9, 0.8-3.6, 0.9-3.3, 1-3.15, or about 1-about 3;
-for trivinyl monomers:
1-4, 1.4-3, 1.5-2.6, 1.6-2.4, 1.8-2.2, 2-2.1, or about 2;
-for a tetravinyl monomer:
1.5-6, 2.1-4.5, 2.25-3.9, 2.4-3.6, 2.7-3.3, 3-3.15, or about 3.
Further, optionally:
generally for polyvinyl monomers:
90% of the vinyl polymer chains comprise less than 10 residues of the multivinyl monomer, or 90% have a length of 7 or less, or 90% have a length of 5 or less, or 90% have a length of 4 or less, or 90% have a length of 3 or less, or 90% have a length of 2 or less, or 95% have a length of 15 or less, or 95% have a length of 10 or less, or 95% have a length of 7 or less, or 95% have a length of 5 or less, or 95% have a length of 4 or less, or 95% have a length of 3 or less, or 75% have a length of 10 or less, or 75% have a length of 7 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less;
-for trivinyl monomers:
90% of the vinyl polymer chains comprise less than 8 TVM residues, or 90% have a length of 5 or less, or 90% have a length of 4 or less, or 95% have a length of 10 or less, or 95% have a length of 8 or less, or 95% have a length of 5 or less, or 75% have a length of 8 or less, or 75% have a length of 6 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less;
-for a tetravinyl monomer:
90% of the vinyl polymer chains comprise less than 6 residues of tetravinyl monomers, or 90% have a length of 4 or less, or 90% have a length of 3 or less, or 90% have a length of 2 or less, or 95% have a length of 8 or less, or 95% have a length of 6 or less, or 95% have a length of 4 or less, or 95% have a length of 3 or less, or 75% have a length of 5 or less, or 75% have a length of 4 or less, or 75% have a length of 3 or less, or 75% have a length of 2 or less.
The branched polymer product may optionally comprise polyvinyl monomer residues and chain transfer residues, wherein each vinyl bond is directly vinyl polymerized to an average of:
generally for polyvinyl monomers:
0.1 to 1.5, 0.2 to 1.2, 0.825 to 1.1, or about 0.3 to 1 other polyvinyl monomer residues;
-for trivinyl monomers:
0.2-1.3, 0.25-1.2, 0.3-1, 0.4-0.7, or about 0.5 other trivinyl monomer residues;
-for a tetravinyl monomer:
0.1-1, 0.2-0.8, 0.25-0.5, or about 0.3 other tetravinyl monomer residues.
The branched polymer product optionally comprises polyvinyl monomer residues and chain transfer residues, wherein the branched polymer product comprises a plurality of vinyl polymer segments having an average length of:
generally for polyvinyl monomers:
1-3, 1-2.5, 1-2.2, 1-2, 1.1-2, 1.2-2, 1.3-2, 1.33-2, 1.5-2, 1.8-2, 1.9-2, 1.95-2, 1.2-1.5, 1.3-1.5, 1.4-1.5, 1.45-1.5, 1.1-1.4, 1.2-1.33, or 1.3-1.33 polyvinyl monomer residues;
-for trivinyl monomers:
1-2, 1-1.8, 1-1.7, 1-1.5, 1.1-1.5, 1.2-1.5, 1.25-1.5, 1.3-1.5, 1.4-1.5, or 1.45-1.5, or about 1.5 trivinyl monomer residues;
-for a tetravinyl monomer:
1-1.7, 1-1.5, 1-1.4, 1-1.33, 1.1-1.33, 1.2-1.33, 1.25-1.33, or 1.3-1.33, or about 1.33 tetraethylene monomer residues.
The incorporation of monovinyl monomers as well as polyvinyl monomers can affect the average vinyl chain length but not the average number of polyvinyl monomer residues per chain. It may be a way to add vinyl chains without adding branching.
The branched polymer product optionally comprises polyvinyl monomer residues and chain transfer residues, wherein the polyvinyl monomer residues comprise less than 20 mol% of double bond functionality. The residue may comprise less than 10 mol%, or less than 5 mol%, or less than 2 mol%, or less than 1 mol%, or substantially no double bond functional groups.
Drawings
The invention will now be described in further non-limiting detail with reference to the accompanying drawings, in which:
FIGS. 1 and 2 show the radical mechanism involved in one embodiment of the present invention;
FIGS. 3 and 4 show schematic diagrams of branched polymers according to one embodiment of the present invention;
FIG. 5 shows NMR spectra at various stages during a polymerization process according to an embodiment of the invention;
FIG. 6 shows examples of some compounds that may be used as divinyl monomers in the present invention;
FIG. 7 shows examples of some compounds that may be used as chain transfer agents in the present invention;
FIG. 8 shows a further schematic of a branched polymer according to the present invention highlighting the vinyl polymer chain length within the product;
FIG. 9 shows a mass spectrum of the components of a polymer according to one embodiment of the present invention;
fig. 10 shows a mass spectrum of the polymer species compared to fig. 9.
FIG. 11 highlights polyester chains within a polymer product according to an embodiment of the invention and indicates theoretically step-growth of synthetic equivalent monomers;
FIGS. 12 to 16 show NMR spectra of some branched polymer products prepared using trivinyl monomers and other reagents; and
FIG. 17 shows a schematic of the components of the divinyl monomer and polymer segments of the present invention.
Detailed Description
Referring to fig. 1, the free radicals are reactively transferred to a chain transfer agent such as dodecyl mercaptan by reacting with a free radical derived from an initiator such as AIBN, or by reacting with a free radical derived from a divinyl monomer (e.g., EGDMA) that has previously reacted with a free radical source. This results in the generation of a chain transfer agent radical [ CH in FIG. 13(CH2)11S·]Which (fig. 2) in the present invention reacts with the divinyl monomer and causes chain propagation.
Schematic diagrams of the resulting branched polymers are shown in fig. 3 and 4. In the case of DDT as chain transfer agent, the circles represent the moiety comprising a dodecyl chain. Although the polymer is built up by vinyl polymerization, the chemistry of the longest chain in the product is still determined by the other functional groups present in the divinyl monomer, and thus, in some embodiments, the longest chain may be a polyester.
One advantage of the present invention is that the vinyl functionality of the monomer can be fully reacted. Experimental evidence for this has been obtained by NMR analysis: in FIG. 5, for the sample at the beginning of the reaction, the top NMR spectrum shows due to the presence of double bond hydrogen1H NMR. After reaction, the NMR trace (bottom) shows no detectable signal for double bonds.
FIG. 8 shows a branched polymer made from divinyl monomer EGDMA and chain transfer agent DDT (shown as spherical). The bold line indicates the C-C bond which was once a double bond in the monomer. The numbers indicate the chain length of the vinyl polymer. It can be seen that there are 13 chains of
The product shown in figure 8 is consistent with the discussion above relating to some standard systems in which there are (n +1) chain transfer agent residues per n divinyl monomer residues and the average vinyl polymer chain length is 2n/(n + 1). The ratio of chain transfer residues to divinyl monomer residues is 26:25, i.e. (n +1): n, such that the number of chain transfer residues per divinyl monomer residue is 26/25 ═ 1.04. The average polymer chain length was [ (1 × 13) + (2 × 5) + (3 × 6) + (4 × 1) + (5 × 1) ]/(13+5+6+1+ 1): 50/26 ═ 1.923, i.e. 2n/(n + 1). All vinyl groups have reacted, i.e. conversion is 100%. Each vinyl residue is directly vinyl polymerized to an average of 48/50 ═ 0.96 other divinyl monomer residues.
If formed by similar step-growth polymerization, the "step-growth monomer residues" formed by vinyl polymerization in the present invention will be derived from a mixture of synthetic equivalents (see FIG. 11) that include some polyfunctional (at least trifunctional) synthetic equivalents (e.g., a polyacid or a polyol) to form branched structures. This would correspond to An+BmStep-growth systems of monomers in which at least one of n or m is greater than 2 and the other is 2 or greater, e.g. A2+B3Monomers or A3+B2A system of monomers. Such systems would be complex to synthesize, stoichiometrically challenging, and plagued by other difficulties including gelation problems.