阅读说明：本技术 一种大分子共组装诱导低χ值聚合物制备均孔膜的方法 (Method for preparing homogeneous pore membrane by macromolecule co-assembly induced low-chi-value polymer ) 是由 易砖 朱国栋 殷煜镕 刘立芬 于 2019-08-13 设计创作，主要内容包括：本发明公开了一种大分子共组装诱导低χ值聚合物制备均孔膜的方法。所述方法选用含有酰胺键或酯键等氢键受体的嵌段聚合物作为成膜材料,利用外源性大分子提供的氢键作用增强嵌段聚合物之间的不相容性,促进嵌段聚合物自组装形成均孔膜。所述方法的过程如下：将嵌段聚合物、氢键给体聚合物、溶剂混合形成均相溶液,用刮刀将铸膜液在基底上铺展开,空气中停留一定时间后浸入凝固浴中相转化成膜。本发明解决了低χ值嵌段聚合在溶液中难以发生微相分离的问题,为均孔膜的制备和性能的提升提供了新的思路,也为不同层面实现均孔膜功能和性能的多样化设计提供了更多选择；通过本发明方法制备得到的膜内部结构更加疏松,强度更强,具有更高的通量。(The invention discloses a method for preparing a uniform pore membrane by inducing a low chi value polymer through macromolecular co-assembly. According to the method, a block polymer containing hydrogen bond receptors such as amido bonds or ester bonds is selected as a film forming material, the incompatibility among the block polymers is enhanced by utilizing the hydrogen bond action provided by exogenous macromolecules, and the self-assembly of the block polymers is promoted to form the homogeneous pore film. The method comprises the following steps: mixing the block polymer, the hydrogen bond donor polymer and the solvent to form a homogeneous solution, spreading the casting solution on a substrate by using a scraper, standing in air for a certain time, and immersing in a coagulating bath for phase conversion to form a film. The invention solves the problem that the low-chi-value block polymerization is difficult to generate microphase separation in the solution, provides a new idea for the preparation and the performance improvement of the homogeneous pore membrane, and also provides more choices for realizing the diversified design of the functions and the performances of the homogeneous pore membrane in different layers; the membrane prepared by the method has a looser internal structure, higher strength and higher flux.)

1. A method for preparing a homogeneous pore membrane by macromolecule co-assembly induced low chi value polymer is characterized by comprising the following steps:

(1) mixing the block polymer, a solvent and an additive to form a homogeneous membrane casting solution; the mass fraction of the block polymer in the casting solution is 3-33 wt%, the block polymer is a block polymer containing an ester bond or amido bond hydrogen bond receptor, and the additive is a hydrogen bond donor polymer; the mass ratio of the additive to the block polymer is 0.01-0.5: 1.

(2) Spreading the casting film liquid on a flat substrate by a scraper, and staying in the air for 5-120s to obtain a primary film;

(3) immersing the primary membrane into a coagulating bath for phase conversion to obtain a homogeneous pore membrane, and finally storing the homogeneous pore membrane in deionized water.

2. The method of claim 1, wherein in step (1), the structure of the block polymer is represented by structural formula (1) or structural formula (2):

wherein the structure of R is selected from the structural formula (3) to the structural formula (6); the structure of R' is selected from structural formula (7) to structural formula (9); r' is an alkane; n and m are natural numbers.

3. The method according to claim 1, wherein in the step (1), the mass of the hydrophilic block in the block polymer accounts for 5-33% of the total mass of the polymer.

4. The method as claimed in claim 1, wherein in the step (1), the solvent is one, two or three of dioxane, pyridine, tetrahydrofuran, propylene glycol propyl ether, dimethylformamide, acetonitrile, methanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and polyethylene glycol with molecular weight less than 500.

5. The method according to claim 1, wherein in the step (1), the additive is selected from polyacrylic acid with a molecular weight of 500-25500 g/mol, polymethacrylic acid, carboxyl-containing hyperbranched polymer, sulfonated polystyrene and the like;

6. the method according to claim 1, wherein in the step (2), the substrate is a flat membrane or a hollow fiber membrane of glass, non-woven fabric, silicon wafer, glass modified by silane coupling agent, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polypropylene.

7. The method of claim 1, wherein the coagulation bath consists of one or two of deionized water, glycerol, ethanol in any ratio.

Technical Field

The invention belongs to the field of novel separation materials, and particularly relates to a block polymer with a weak phase separation tendency and a method for preparing a homogeneous pore membrane by using the block polymer.

Background

Homogeneous pore membranes, by virtue of their uniform pore size and relatively high porosity, can significantly improve separation accuracy and separation efficiency, and have recently been widely studied in the field of membrane technology. The block polymers currently used for preparing the mesoporous film are mostly polymers (such as polystyrene-block-polytetra ethylene pyridine, polystyrene-block-polyacrylic acid and related derivatives) with high phase separation capacity (Flory interaction parameter x is more than 0.2). However, the number of the polymers is small, so that the selection of materials of the homogeneous pore membrane is greatly limited; meanwhile, many polymers with weaker phase separation tendency have good performances such as stimulus responsiveness, high temperature resistance, flexibility and toughness, can endow the mesoporous membrane with more and better functions, and provide convenience for practical application.

However, the formation of block polymer based mesoporous films relies primarily on the self-assembly of block polymers into ordered structures under specific thermodynamic conditions. The low-chi-value block polymerization is difficult to generate microphase separation in a solution, which brings great inconvenience to the preparation of the mesoporous membrane by adopting the polymer, and is one of the reasons that the low-chi-value block polymerization is adopted to prepare the mesoporous membrane so far. At present, the conditions for preparing the mesoporous membrane by adopting the polymer are harsh, the polymer is generally required to have higher molecular weight, the membrane casting solution has higher concentration, and the types and the proportions of the solvents are relatively fixed, which are not beneficial to the regulation and control of the structure of the mesoporous membrane. Meanwhile, the problem of phase separation cannot be fundamentally solved, so that the obtained membrane is relatively compact and has low flux.

Disclosure of Invention

The invention aims to provide a method for preparing a uniform pore membrane by co-assembling a low-chi-value induced polymer, aiming at the defects of the prior art, and effectively solving the problems of weak phase separation tendency and difficult self-assembly of a block polymer in the membrane forming process.

The invention adopts the following technical scheme:

1. a method for preparing a homogeneous pore membrane by macromolecule co-assembly induced low chi value polymer comprises the following steps:

(1) mixing the block polymer, a solvent and an additive to form a homogeneous membrane casting solution; the mass fraction of the block polymer in the casting solution is 3-33 wt%, the block polymer is a block polymer containing a hydrogen bond receptor such as an ester bond or an amido bond, and the additive is a hydrogen bond donor polymer; the mass ratio of the additive to the block polymer is 0.01-0.5: 1.

(2) Spreading the casting film liquid on a flat substrate by a scraper, and staying in the air for 5-120s to obtain a primary film;

(3) immersing the primary membrane into a coagulating bath for phase conversion to obtain a homogeneous pore membrane, and finally storing the homogeneous pore membrane in deionized water.

Further, the structural formula (1) or the structural formula (2):

wherein the structure of R is selected from the structural formula (3) to the structural formula (6); the structure of R' is selected from structural formula (7) to structural formula (9); r' is an alkane; n and m are natural numbers.

Further, in the step (1), the mass ratio of the hydrophobic block to the hydrophilic block in the block polymer is 2-20: 1.

Further, in the step (1), the solvent is composed of one, two or three of dioxane, pyridine, tetrahydrofuran, propylene glycol propyl ether, dimethylformamide, dimethylacetamide, acetonitrile, methanol, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and polyethylene glycol with molecular weight less than 500 according to any ratio.

Further, in the step (1), the additive is selected from polyacrylic acid with the molecular weight of 500-25500 g/mol, polymethacrylic acid, carboxyl-containing hyperbranched polymer, sulfonated polystyrene and the like;

further, in the step (2), the substrate is a flat membrane or a hollow fiber membrane of glass, non-woven fabric, silicon wafer, glass modified by a silane coupling agent, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polypropylene.

Further, the coagulating bath is composed of one or two of deionized water, glycerol and ethanol according to any ratio.

The invention has the beneficial effects that: according to the invention, macromolecules are introduced as additives in the process of preparing the mesoporous membrane by the SNIPS method, so that the phase separation is enhanced, the problem that the microphase separation of low-chi-value block polymerization in a solution is difficult to occur is solved, a new thought is provided for the preparation and performance improvement of the mesoporous membrane, the requirements of the preparation of the mesoporous membrane by the SNIPS method on polymers are reduced, the selection range of raw materials is widened, and more choices are provided for realizing the diversified design of functions and performances of the mesoporous membrane at different layers; the membrane prepared by the method has a looser internal structure, higher strength and higher flux.

Drawings

FIG. 1: nuclear magnetic spectrum of a block polymer, wherein a is the block polymer prepared in example 1, b is the block polymer prepared in example 2, and c is the block polymer prepared in example 3;

FIG. 2: detecting the supermolecule effect by infrared;

FIG. 3: a homogeneous pore membrane forming structure, wherein a is the homogeneous pore membrane prepared in example 1, b is the homogeneous pore membrane prepared in example 2, and c is the homogeneous pore membrane prepared in example 3;

FIG. 4: an X-ray small angle scattering pattern.

Detailed Description

The invention takes the block polymer containing polyacrylamide, polyester and the like with hydrogen bond acceptors as a main film forming material, overcomes the problem of difficult self-assembly by adopting a simple co-assembly method on the basis of the original SNIPS method, and brings convenience for preparing the homogeneous pore film by using the block polymer with low chi value. The specific scheme is that a polymer additive which has strong repulsion with a hydrophobic block and can interact with a hydrophilic block is selected, and the additive is dynamically connected to the hydrophilic end of the block polymer through intermolecular force to promote the cooperative assembly of the block polymer; and the repulsion force between the additive and the hydrophobic block is utilized to promote the hydrophilic block and the hydrophobic block to be separated, so that the incompatibility between the two blocks of the polymer is improved, and the homogeneous pore membrane is formed by self-assembly. The introduction of the additive greatly reduces the requirements of the formation of the homogeneous pore membrane on the molecular weight of the polymer and the membrane forming conditions. In addition, the introduction of the additive enhances phase separation, and the prepared membrane has a looser internal structure and higher flux.