阅读说明：本技术 一种电致发光聚合物分子量窄化处理的方法 (Method for narrowing molecular weight of electroluminescent polymer ) 是由 应磊 曹镛 于 2020-12-29 设计创作，主要内容包括：本发明属于分析纯化领域,公开了一种电致发光聚合物分子量窄化处理的方法。该方法包括以下步骤：将需要分子量窄化的电致发光聚合物,用有机溶剂1溶解,转移至透析袋中,置于装有有机溶剂2的容器中,然后进行搅拌窄化；再将透析袋取出,将袋内溶剂浓缩,烘干即得分子量窄化的电致发光聚合物。通过本发明的分子量窄化方法处理后的电致发光聚合物的分子量分布进一步窄化,有效规避了小分子量的电致发光对成膜质量、荧光量子产率、热力学性能的影响。用于制备聚合物电致发光器件,可以有效提高发光效率和功耗,改善器件的寿命。(The invention belongs to the field of analysis and purification, and discloses a method for narrowing the molecular weight of an electroluminescent polymer. The method comprises the following steps: dissolving an electroluminescent polymer with a required molecular weight narrowing by using an organic solvent 1, transferring the electroluminescent polymer into a dialysis bag, placing the dialysis bag into a container filled with an organic solvent 2, and then stirring and narrowing; and taking out the dialysis bag, concentrating the solvent in the bag, and drying to obtain the electroluminescent polymer with narrowed molecular weight. The molecular weight distribution of the electroluminescent polymer treated by the molecular weight narrowing method is further narrowed, and the influence of electroluminescence with small molecular weight on film forming quality, fluorescence quantum yield and thermodynamic performance is effectively avoided. The preparation method is used for preparing the polymer electroluminescent device, and can effectively improve the luminous efficiency and the power consumption and improve the service life of the device.)

1. A method for narrowing the molecular weight of an electroluminescent polymer, comprising the steps of: dissolving an electroluminescent polymer with a required molecular weight narrowing by using an organic solvent 1, transferring the electroluminescent polymer into a dialysis bag, placing the dialysis bag into a container filled with an organic solvent 2, and then stirring and narrowing; and taking out the dialysis bag, concentrating the solvent in the bag, and drying to obtain the electroluminescent polymer with narrowed molecular weight.

2. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the organic solvent 1 is the same as the organic solvent 2 and is at least one of dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, toluene, xylene and chlorobenzene.

3. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the ratio of the volume of the organic solvent 1, the volume of the organic solvent 2 and the mass of the electroluminescent polymer is 50-200 ml: 2-20 ml:1 g.

4. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the dialysis bag is made of regenerated cellulose membrane or ultrafiltration membrane.

5. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the dialysis bag is made of an ultrafiltration membrane.

6. The method of molecular weight narrowing of electroluminescent polymer according to claim 4 or 5, wherein:

the specification of the regenerated cellulose membrane is MWCO 6000-8000D, 8000-12000D or 12000-14000D; the specification of the ultrafiltration membrane is 30000, 50000, 60000, 100000, 200000 or 300000.

7. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the temperature for stirring and narrowing is 10-100 ℃;

the stirring narrowing time is 2-36 h.

8. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the temperature for stirring and narrowing is 30-80 ℃;

the stirring narrowing time is 10-24 h.

9. The method of molecular weight narrowing of electroluminescent polymer according to claim 1, wherein:

the steps are repeated for more than three times.

10. The method for molecular weight narrowing of electroluminescent polymers according to claim 1, characterized in that it comprises in particular the following steps:

the method comprises the following steps: completely dissolving 1 part by mass of electroluminescent polymer to be purified by using 2-20 parts by mass of organic solvent, and transferring into a dialysis bag; then placing the mixture into a container which is pre-filled with 50-200 parts by mass of organic solvent, and stirring the mixture for 2-36 hours at the temperature of 10-100 ℃;

step two: and (3) balancing the temperature of the system obtained in the step one to room temperature, taking out the bag, concentrating the solvent in the bag, and drying to obtain the electroluminescent polymer with narrowed molecular weight.

Technical Field

The invention belongs to the field of analysis and purification, and particularly relates to a method for narrowing the molecular weight of an electroluminescent polymer.

Background

Organic Light Emitting Diodes (OLEDs) are receiving high attention from academia and industry as a new generation of flat panel display technology. The OLED has the advantages of flexibility, active light emission, high efficiency, low-voltage driving, easiness in preparation of large-area devices and the like, but the problems of low luminous efficiency, short service life of the devices, high difficulty in volume production and the like of blue light materials block the practicability and industrialization of the OLED. The development of organic electroluminescent materials with high efficiency and stable mass production and the optimization of the device preparation process are still main solutions for promoting the further development of the OLED display screen.

In the working process of the OLED device, a certain voltage is applied between two electrodes of the light-emitting device, holes and electrons in the material of the light-emitting layer are transferred under the action of an electric field, excitons are formed in the light-emitting layer, and the excitons release photons through recombination. Taking polymer electroluminescence as an example, in the case of a polymer electroluminescent device, when an external circuit is switched on, holes and electrons are injected from an anode and a cathode respectively under the action of an external electric field, the holes are injected to the highest occupied orbital (HOMO) of a polymer by overcoming an energy barrier between the anode and a polymer light emitting layer, the electrons are injected to the lowest unoccupied orbital (LUMO) of the polymer by overcoming an energy barrier between the cathode and the polymer light emitting layer, the holes and the electrons meet in the light emitting layer to form excitons through the action of coulomb force, the excitons are recombined to jump from an excited state (S1) to a ground state (S0), and redundant energy is released in the form of photons. The luminescence process comprises several processes of carrier injection, carrier transmission, exciton formation by electron and hole collision, exciton diffusion migration and radiative decay to release photons.

Polymers are widely used in polymer electroluminescent devices due to their unique advantages of being solution processable into large area flexible devices. The polymer has natural polydispersity, is a mixture, and has better film-forming quality and large conjugation degree when the molecular weight is larger than that of a small-molecular-weight polymer, better thermodynamic performance, higher fluorescence quantum yield and better device performance. However, due to different preparation batches and different molecular weights and multi-distribution coefficients, the electroluminescent properties of the prepared devices are different, and the reproducibility is poor, so that the problem can be effectively avoided by obtaining polymers with the same molecular weight distribution as much as possible.

Dialysis has become one of the most convenient and commonly used separation and purification techniques in biological and chemical laboratories. In the preparation process of biological macromolecules, dialysis techniques are used for desalting, removing a small amount of organic solvent, removing biological micromolecular impurities, concentrating samples and the like. In the prior art, the dialysis bag is only used for removing the water-soluble substances and is not good for the restraint of the oil-soluble substances, so that the purification of the oil-soluble substances, especially the organic electroluminescent polymer, can be effectively simplified by adopting the dialysis bag capable of removing the oil-soluble substances, the performance of the electroluminescent device is improved, and the further industrialization of the electroluminescent device is promoted.

Disclosure of Invention

In order to overcome the disadvantages and shortcomings of the prior art, the invention provides a method for narrowing the molecular weight of an electroluminescent polymer. The purification method is simple and convenient to operate, easy in post-treatment and has great application potential.

The purpose of the invention is realized by the following scheme:

a method for the molecular weight narrowing treatment of an electroluminescent polymer comprises the following steps: dissolving an electroluminescent polymer with a required molecular weight narrowing by using an organic solvent 1, transferring the electroluminescent polymer into a dialysis bag, placing the dialysis bag into a container filled with an organic solvent 2, and then stirring and narrowing; and taking out the dialysis bag, concentrating the solvent in the bag, and drying to obtain the electroluminescent polymer with narrowed molecular weight.

The organic solvent 1 is the same as the organic solvent 2, is at least one of dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, toluene, xylene and chlorobenzene, and is preferably one of tetrahydrofuran, dichloromethane and toluene;

the ratio of the volume of the organic solvent 1 to the volume of the organic solvent 2 to the mass of the electroluminescent polymer is 50-200 ml: 2-20 ml:1g, preferably 80-150 ml: 5-15 ml:1g, and more preferably 100ml:10ml:1 g.

The dialysis bag is made of regenerated cellulose membrane or ultrafiltration membrane. The specification of the regenerated cellulose membrane is MWCO 6000-8000D, 8000-12000D or 12000-14000D; the ultrafiltration membrane specification is 30000, 50000, 60000, 100000, 200000 or 300000. Dialysis bags of ultrafiltration membrane material are preferred.

The temperature for stirring and narrowing is 10-100 ℃, preferably 30-80 ℃, and more preferably 60 ℃; the time for stirring to narrow is 2-36h, preferably 10-24 h. Too short a time period cannot achieve the purpose of removing the polymer with a specific molecular weight, and too long a time period increases the process cost.

The specific purification steps are as follows:

the method comprises the following steps: completely dissolving 1 part by mass of electroluminescent polymer to be purified by using 2-20 parts by mass of organic solvent, and transferring into a dialysis bag. Then placing the mixture into a container which is pre-filled with 50-200 parts by mass of organic solvent, and stirring the mixture for 2-36 hours at the temperature of 10-100 ℃;

step two: and (3) balancing the temperature of the system obtained in the step one to room temperature, taking out the bag, concentrating the solvent in the bag, and drying to obtain the electroluminescent polymer with narrowed molecular weight.

The molecular weight can be intercepted by a dialysis bag made of a regenerated cellulose membrane or an ultrafiltration membrane, namely, under a certain condition, substances with certain molecular weight are intercepted, and the minimum molecular weight of the intercepted substances is the intercepted molecular weight of the membrane. The molecular weight narrowing method of the invention can effectively remove the electroluminescent polymer with small molecular weight and obtain the electroluminescent polymer with specific large molecular weight.

The purification is carried out by more than three stirring steps, and the effect of narrowing the molecular weight is better.

The method for narrowing the molecular weight of the electroluminescent polymer is to stir at a specific temperature in a container, wherein the container can be a beaker, a plastic barrel, a single-mouth bottle, a two-mouth bottle, a three-mouth bottle or a reaction kettle, and the like, and the preferred temperature of 30-80 ℃ can accelerate the diffusion rate of the electroluminescent polymer in a dialysis bag and accelerate the electroluminescent polymer with the molecular weight smaller than the specification of the dialysis bag to diffuse outside the dialysis bag, so that the capability of the dialysis bag for intercepting the electroluminescent polymer is improved.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the molecular weight distribution of the electroluminescent polymer treated by the molecular weight narrowing method is further narrowed, and the influence of electroluminescence with small molecular weight on film forming quality, fluorescence quantum yield and thermodynamic performance is effectively avoided. The preparation method is used for preparing the polymer electroluminescent device, and can effectively improve the luminous efficiency and the power consumption and improve the service life of the device. The method for narrowing the molecular weight of the electroluminescent polymer of the invention stirs at high temperature through the container, not only has low process cost, but also has simple and convenient operation and easy post-treatment. The method for narrowing the molecular weight of the electroluminescent polymer adopts wide-mouth containers which can be satisfied in laboratories or production lines, has low requirement on operating devices, has no strict limitation, and can be containers such as beakers, plastic barrels, single-mouth bottles, two-mouth bottles, three-mouth bottles or reaction kettles and the like. The invention has no strict company restriction requirements on the electroluminescent polymer and has universality.

Drawings

FIG. 1 is a UV-visible absorption spectrum of PFO in a toluene solvent before and after purification in example 1.

Fig. 2 is a graph of current efficiency versus current density for PFO-based electroluminescent devices before and after purification in example 2.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In the examples, poly (9, 9-di-n-octylfluorenyl-2, 7-diyl) (PFO), poly [ (9, 9-dioctylfluorene-2, 7-diyl) -alt- (2,1, 3-benzothiadiazol-4, 7-diyl) ] (F8BT), poly (2, 5-dibutoxybenzene-1, 4-diyl) (Bu-PPP), etc. are commercially available, and no particular limitation is imposed on the suppliers.

Example 1

A method for narrowing the molecular weight of poly (9, 9-di-n-octylfluorenyl-2, 7-diyl) (PFO) takes PFO (number average molecular weight (Mn) of 20000 to 40000) which is a product of Sianbaolaite opto-electronic technology Limited as an example, and comprises the following steps:

the method comprises the following steps: 1.0g of poly (9, 9-di-n-octylfluorenyl-2, 7-diyl) (PFO) having a number average molecular weight of 20000 to 40000 was completely dissolved in 10ml of methylene chloride, transferred to a dialysis bag (available from New technology, Inc., Aldara, Dongguan) made of an ultrafiltration membrane and having a specification of 30000, and added to a beaker previously filled with 100ml of methylene chloride, heated to 40 ℃ and stirred for 10 hours.

Step two: and (4) after the system obtained in the step one is cooled to room temperature, collecting a dichloromethane organic phase, concentrating and drying.

Step three: and (4) repeatedly treating the PFO dried in the step two for 3 times according to the step one to obtain the PFO with narrowed molecular weight.

The standard curve was prepared using a Waters GPC 2410 Gel Permeation Chromatograph (GPC) instrument with THF as eluent and monodisperse polystyrene of known molecular weight as reference. PFO, a product of Simanbaolet opto-electronic technology, Inc., has a number average molecular weight (Mn) of 20000 to 40000 and a polydispersity number PDI of 2.0. After the molecular weight narrowing treatment of the PFO-PF. The effectiveness of the molecular weight narrowing treatment method of the present invention is demonstrated.

The electroluminescent polymers before and after the narrowing of the molecular weight of the above examples were subjected to test analysis using an ultraviolet-visible spectrophotometer (model agilent cary 60, ag ilent corporation). FIG. 1 shows the UV-visible absorption spectra of PFO in toluene solvent before and after molecular weight narrowing, without any change in the spectra, indicating that the polymer treated by molecular weight narrowing according to the present invention can still maintain the original properties.

The fluorescence quantum yield of PFO in toluene solvent before and after molecular weight narrowing is measured by an HAMAMATSU C11347 absolute fluorescence quantum yield spectrometer through an integrating sphere, which shows that the fluorescence quantum yield of the polymer subjected to molecular weight narrowing treatment is improved from original 67% to 75%.

Example 2

A method for narrowing the molecular weight of poly (9, 9-di-n-octylfluorenyl-2, 7-diyl) (PFO) takes PFO (number average molecular weight (Mn) of 30000 to 60000) which is a product of Sianbaolaite opto-electronic technology Limited as an example, and comprises the following steps:

the method comprises the following steps: 1.0g of poly (9, 9-di-n-octylfluorenyl-2, 7-diyl) (PFO) having a number average molecular weight of 30000 to 60000 was completely dissolved in 10ml of toluene, transferred to a 50000-sized dialysis bag (available from New materials science and technology Co., Ltd., Dongguan) made of an ultrafiltration membrane, and added to a beaker previously filled with 100ml of toluene, and the mixture was heated to 60 ℃ and stirred for 10 hours.

Step two: and (4) after the system obtained in the step one is cooled to room temperature, collecting a dichloromethane organic phase, concentrating and drying.

Step three: and (4) repeatedly treating the PFO dried in the step two for 3 times according to the step one to obtain the PFO with narrowed molecular weight.

The standard curve was prepared using a Waters GPC 2410 Gel Permeation Chromatograph (GPC) instrument with THF as eluent and monodisperse polystyrene of known molecular weight as reference. The PFO product of Simanbaolet opto-electronic technology Limited has a number average molecular weight (Mn) of 30000-60000 and a polydispersity PDI of 2.0. After the molecular weight narrowing treatment of the PFO-PFO molecular weight narrowing treatment method, the number average molecular weight of the PFO-PFO is 50520-60000, and the polydispersity number PDI is only.

The fluorescence quantum yield of PFO in toluene solvent before and after molecular weight narrowing is measured by an HAMAMATSU C11347 absolute fluorescence quantum yield spectrometer through an integrating sphere, which shows that the fluorescence quantum yield of the polymer subjected to molecular weight narrowing treatment is improved from 69% to 80%.

Example 3

A method for narrowing the molecular weight of poly [ (9, 9-dioctylfluorene-2, 7-diyl) -alt- (2,1, 3-benzothiadiazole-4, 7-diyl) ] (F8BT) is exemplified by F8BT (molecular weight (Mn) is 10000-100000) manufactured by Xianbaolite opto-electronic technology Limited company, and comprises the following steps:

the method comprises the following steps: 1.0g of poly [ (9, 9-dioctylfluorene-2, 7-diyl) -alt- (2,1, 3-benzothiadiazole-4, 7-diyl) ] (F8BT) was completely dissolved in 10ml of toluene, and then transferred to a 50000-sized dialysis bag (available from Arda technologies, Inc., Dongguan) made of an ultrafiltration membrane, and the solution was added to a beaker previously filled with 100ml of toluene, heated to 60 ℃ and stirred for 10 hours.

Step two: and (4) after the system obtained in the step one is cooled to room temperature, collecting a dichloromethane organic phase, concentrating and drying.

Step three: and (3) repeatedly treating the dried PFO obtained in the second step for 3 times according to the first step to obtain F8BT with narrowed molecular weight.

The standard curve was prepared using a Waters GPC 2410 Gel Permeation Chromatograph (GPC) instrument with THF as eluent and monodisperse polystyrene of known molecular weight as reference. The number average molecular weight (Mn) of F8BT, a product of Xianbaolite photoelectric technology Limited, is 37400-78700, and the polydispersity number PDI is 2.10. After the molecular weight narrowing treatment of the invention, the number average molecular weight of F8BT is 50140-78400, and the polydispersity PDI is only 1.57.

The fluorescence quantum yield of F8BT in toluene solvent before and after molecular weight narrowing was measured by an integrating sphere using HAMAMATSU C11347 absolute fluorescence quantum yield spectrometer, which indicates that the fluorescence quantum yield of the polymer subjected to molecular weight narrowing treatment of the invention is improved from original 72% to 89%.

Example 4

A method for narrowing the molecular weight of poly (2, 5-dibutoxybenzene-1, 4-diyl) (Bu-PPP), as exemplified by F8BT (molecular weight (Mn) of 10000 to 100000) manufactured by Siennan Baolaite photoelectric technology Limited, comprises the steps of:

the method comprises the following steps: 1.0g of poly (2, 5-dibutoxybenzene-1, 4-diyl) (Bu-PPP) was completely dissolved in 10ml of toluene, transferred to a dialysis bag (available from Dongguan Aldar New materials science and technology Co., Ltd.) made of an ultrafiltration membrane and having a standard of 60000, and added to a beaker previously charged with 100ml of toluene, and the mixture was heated to 60 ℃ and stirred for 10 hours.

Step two: and (4) after the system obtained in the step one is cooled to room temperature, collecting a dichloromethane organic phase, concentrating and drying.

Step three: and (3) repeatedly treating the Bu-PPP dried in the step two according to the step one for 3 times to obtain the Bu-PPP with the narrowed molecular weight.

The standard curve was prepared using a Waters GPC 2410 Gel Permeation Chromatograph (GPC) instrument with THF as eluent and monodisperse polystyrene of known molecular weight as reference. The Bu-PPP product of the Xianbaoliet opto-electronic technology Limited company has a number average molecular weight (Mn) of 48700-85300 and a polydispersity number PDI of 1.75. After the molecular weight narrowing treatment of the invention, the number average molecular weight of F8BT is 60850-85300, and the polydispersity PDI is only 1.40.

The fluorescence quantum yield of Bu-PPP in toluene solvent before and after molecular weight narrowing is measured by an HAMAMATSU C11347 absolute fluorescence quantum yield spectrometer through an integrating sphere, which shows that the fluorescence quantum yield of the polymer subjected to molecular weight narrowing treatment is improved to 67 percent from original 46 percent.

Example 5

PFO before and after purification in example 2, and F8BT before and after purification in example 3 were used as light-emitting layers to prepare electroluminescent devices. The method comprises the following specific steps:

1) and (5) cleaning the ITO conductive glass. The ITO glass substrate is placed on a film washing frame and is ultrasonically cleaned by an ultrasonic device, and acetone, isopropanol, detergent, deionized water and isopropanol are sequentially used as a cleaning solution, so that the aim of fully removing the possibly residual stains such as photoresist and the like on the surface of the ITO glass substrate and improving interface contact is fulfilled. Then drying in a vacuum oven;

2) placing the ITO in an oxygen plasma etcher using an oxygen plasma (O)₂Plasma) bombarding for twenty minutes to thoroughly remove possible residual organic matters on the surface of the ITO glass substrate;

3) PSS (Baytron P4083) was spin-coated on ITO with a hole injection layer PEDOT 40nm thick, and then dried in a vacuum oven at 80 ℃ for 12 hours;

4) in a glove box in nitrogen atmosphere, a star-shaped electroluminescent material film with the thickness of 80nm is spin-coated on a PEDOT (power stabilizer) PSS layer, and then the star-shaped electroluminescent material film is heated and annealed for 20 minutes at the temperature of 80 ℃ on a heating table to remove residual solvent and improve the appearance of the luminescent layer film;

5) in the vacuum evaporation chamber, the temperature is lower than 3 x 10^-4A layer of cesium fluoride (CsF) with the thickness of 1.5nm is evaporated on the organic film under the vacuum degree of Pa, so that electron injection is facilitated. A 110nm thick aluminum cathode (Al) was then evaporated onto the CsF, where the cesium fluoride and aluminum layers were vacuum deposited through a shadow mask.

The effective area of the device is 0.1cm². The thickness of the organic layer was measured with a quartz crystal monitoring thickness gauge. After the device is prepared, epoxy resin and thin-layer glass are used for polar curing in ultraviolet light and packaging. The single-layer device structure is (ITO/PEDOT: PSS/polymer (80nm)/CsF (1.5nm)/Al (110 nm)).

The obtained electroluminescent device was subjected to a photoelectric property test, and the test results are shown in Table 1 for the electroluminescent properties of the polymer treated by the purification method of the present inventionCan be obviously improved. The curve of the relationship between the lumen efficiency and the current density of the PFO-based electroluminescent device before and after purification in example 2 is shown in FIG. 2, the maximum lumen efficiency of the PFO-based electroluminescent device is improved from 0.67cd/A to 1.83cd/A, which is improved by about 2.7 times, and the luminance is 3950cd/m²Increased to 9194cd/m²The brightness is improved by about 2.3 times, the starting voltage is reduced by 3.6V from 4.0V, and the color coordinate is kept unchanged. The maximum lumen efficiency of the electroluminescent device based on F8BT in example 3 is improved from 0.56cd/A to 3.54cd/A, the performance is improved by about 6.3 times, and the brightness is 4667cd/m²Increased to 10963cd/m²The brightness is improved by about 2.3 times, the starting voltage is reduced by 3.8V from 4.2V, and the color coordinate is kept unchanged. The results show that the electroluminescent properties of the polymers PFO and F8BT are improved after the molecular weight narrowing process of the invention, and the electroluminescent properties of the device are not negatively affected.

Table 1 electroluminescent property data of electroluminescent polymers

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.