CN114044905A

CN114044905A - Preparation method of end group functionalized polydimethylsiloxane

Info

Publication number: CN114044905A
Application number: CN202111172465.1A
Authority: CN
Inventors: 何军坡; 奥斯曼·沙迪; 何立挺
Original assignee: Fudan University
Current assignee: Fudan University
Priority date: 2021-10-06
Filing date: 2021-10-06
Publication date: 2022-02-15
Anticipated expiration: 2041-10-06
Also published as: CN114044905B

Abstract

The invention belongs to the technical field of polydimethylsiloxane preparation, and particularly relates to a preparation method of end-group functionalized polydimethylsiloxane. The invention further initiates anionic polymerization of hexamethylcyclotrisiloxane monomer to prepare end group functionalized polydimethylsiloxane by initiator structure design, which specifically comprises the following steps: designing and preparing a functional initiator; selecting a solvent; and performing post-treatment such as precipitation separation of a product and the like. The invention provides a new high-efficiency and convenient synthetic approach for preparing various end group functionalized polydimethylsiloxane. The initiator structure can be flexibly designed, the synthesis of various end-machine functional polymers can be realized, the polymers can be synthesized at room temperature, the energy consumption is greatly reduced, the deprotection is carried out at normal pressure and room temperature, the past high-temperature and pressure mode is avoided, the energy consumption is reduced in the industrial production, and the production safety is improved.

Description

Preparation method of end group functionalized polydimethylsiloxane

Technical Field

The invention belongs to the technical field of polydimethylsiloxane preparation, and particularly relates to a method for synthesizing polydimethylsiloxane with carboxyl, amino and dimethyl silicon as end groups.

Background

Poly (dimethylsiloxane) (PDMS) is a well-known silicone oil or silicone elastomer that has attracted scientific attention over the past several decades. It has the unique properties of good thermal stability, chain elasticity, good biocompatibility, high oxygen permeability and the like. The remote polydiphenylenediamine is readily synthesized by acid-base ring opening polymerization of hexamethylcyclotetrasiloxane (D4). However, the molecular weight distribution of the final product is broad, and cyclic oligomers are inevitably produced during the polymerization. In addition, in order to synthesize a clear PDMS, hexamethylcyclotrisiloxane (D3) was used as a monomer, which increased the ring tension and faster the living anionic polymerization than the ring-opening polymerization catalyzed by D4. Organolithium-initiated living anionic polymerization is the only method to synthesize structurally defined PDMS. However, the greatest challenge of this method is that the starting material must be highly purified to avoid side reactions such as back-biting, termination, chain transfer, etc. At room temperature, D3 is polymerized in the presence of a non-polar solvent such as cyclohexane, toluene, or a mixture of two solvents, in the presence of a promoter such as tetrahydrofuran, diethylene glycol, or dimethyl sulfoxide. PDMS with two identical or different reactive end groups can be used as a precursor for cross-linkers, chain extenders and block and graft copolymers. The synthesis of PDMS using functionalized organolithium initiators ensured quantitative chain end functionalization. Therefore, a protecting group must be used in the organolithium initiator because the instability of the protecting group during polymerization affects the structure of the final product. Suitable protecting groups are those which survive the conditions of polymerization and which can be readily removed after polymerization without destroying the polymer backbone. In this context, Long and Elkins (C.L.Elkins and T.E.Long, Macromolecules,2004,37,6657-6659) introduce a secondary amine group into the PDMS chain by functionalizing the protective initiator 3- [ (n-benzyl-n-methyl) amino ] -1-propyllithium. The secondary amine is protected by benzyl groups, which are removed after the palladium catalyst polymerization without damaging the PDMS backbone. However, in their work, deprotection requires harsh conditions, such as high temperature and pressure, to ensure functionalized PDMS. Therefore, the invention adopts a novel initiator containing protected functionalization to initiate D3 to obtain PDMS, and further carries out hydrolysis reaction under the condition of normal pressure and room temperature, and finally obtains the polydimethylsiloxane with different end group functionalization.

Disclosure of Invention

The invention aims to provide a method for preparing end-group functionalized polydimethylsiloxane with high efficiency, convenience and energy conservation.

The preparation method of the end group functionalized polydimethylsiloxane provided by the invention comprises the following specific steps:

(1) preparing a compound solution: under vacuum conditions, compound a and a solvent were added to a two-necked reaction flask to obtain a mixed solution. The compound A is selected from Hexamethyldisilazane (Hexamethyl disilazane), Methyl 5-bromothiophene-2-carboxylate (5-Bromo-thiophene-2-carboxylic acid Methyl ester), tert-butyl 4-Bromobenzoate (tert-butyl-4-Bromobenzoate), 4-Bromo-N, N-bis (trimethylsilyl) aniline (4-Bromo-N, N-bis (trimethylsilyl) aniline), Methyl 5-Bromo-2-furoate (Methyl 5-Bromo-2-furoate), tert-butyl 4-Bromo-3-methylbenzoate (4-Bromo-3-methylbenzoic acid tert-butyl ester), and derivatives thereof. The solvent is one of Tetrahydrofuran (THF), Cyclohexane (Cyclohexane), n-Hexane (Hexane) or Diethyl Ether (Diethyl Ether). Wherein, the compound A accounts for 110 parts by weight, and the solvent accounts for 3000 parts by weight; drying the solvent by a reagent purification instrument;

(2) the preparation of the initiator is divided into two methods:

(a) when the solvent used in the step (1) is Tetrahydrofuran (THF) solvent, firstly cooling the mixed solution to-78 ℃, then dropwise adding 60-160 parts of n-butyllithium (n-BuLi) into the mixed solution under vacuum condition, and reacting for 1-3 hours at-78 ℃ to prepare the initiator.

(b) And (2) when the solvent used in the step (1) is other solvents, directly dropwise adding 60-160 parts of n-butyllithium (n-BuLi) into the mixed solution in the step (1) at 20-30 ℃ under vacuum condition, and reacting for 1-3 hours to prepare the initiator.

(3) Adding 3000 parts of solvent 2000-and 600 parts of Hexamethylcyclotrisiloxane (D3) monomer into a two-mouth bottle under vacuum condition; the solvent is the same as that in the step (1);

if Tetrahydrofuran (THF) is selected as a reaction solvent, cooling the system to-10 to-15 ℃, then adding the initiator prepared in the step (2-a) into the system, and stirring and reacting for 1-2 hours under the condition of keeping the temperature from-10 to-15 ℃;

if the reaction solvent is cyclohexane or other solvents, adding the initiator prepared in the step (2-b) into the system, and reacting for 12-16 hours at room temperature.

(4) And (3) dropwise adding 44-66 parts of dimethylchlorosilane (chlorodimethylchlorosilane) which is distilled and purified in advance into the reaction system in the step (3) to perform coupling termination reaction, and after dropwise adding, continuing to react for 8-12 hours at room temperature.

(5) And (3) post-treatment: after the reaction is finished, carrying out reduced pressure distillation on the reaction solution to obtain an oily transparent liquid crude product; then repeatedly carrying out precipitation for 5-8 times in 20000-30000 parts of methanol (MeOH); filtering and drying to obtain pure product with yield higher than 70%.

(6) Hydrolysis: and (3) hydrolyzing the product obtained in the step (5) in 1200 parts of trifluoroacetic acid (TFA) 800-solution or 800 parts of 20 percent sodium hydroxide (NaOH) aqueous solution 1000-1600 parts/ethanol solution 400-800 parts for 8-13 hours to obtain the carboxyl, amino and dimethyl silicon end group functionalized polydimethylsiloxane.

Wherein the components are calculated according to parts by mass.

In the present invention, the solvent is preferably Tetrahydrofuran (THF) or Cyclohexane (Cyclohexane).

In the invention, the compound for preparing the functionalized initiator is one selected from hexamethyldisilazane, methyl 5-bromothiophene-2-carboxylate, tert-butyl 4-bromobenzoate, 4-bromo-N, N-bis (trimethylsilyl) aniline, methyl 5-bromo-2-furoate, tert-butyl 4-bromo-3-methylbenzoate and derivatives thereof.

In the step (1) of the present invention, it is preferred that the amount of the compound A is 100-110 parts.

In step (2) of the present invention, it is preferred that n-butyllithium (n-BuLi) be contained in an amount of 60 to 160 parts (note: the molar ratio of n-butyllithium to the compound A is less than 1).

In the invention, the compounds used for synthesizing the initiator are compounds with different functional structures, and the introduction of the functional structures provides conditions for the functionalization of the polymer.

The invention has the beneficial effects that: the method provides a new efficient and convenient synthetic approach for preparing various end group functionalized polydimethylsiloxane. The initiator structure can be flexibly designed, the synthesis of various end-machine functional polymers can be realized, the polymers can be synthesized at room temperature, the energy consumption is greatly reduced, the deprotection is carried out at normal pressure and room temperature, the past high-temperature and pressure mode is avoided, the energy consumption is reduced in the industrial production, and the production safety is improved.

Drawings

FIG. 1 shows the GPC measurement results before and after hydrolysis of the polymer in example 2. Wherein the dotted curve is before hydrolysis and the solid curve is after hydrolysis.

FIG. 2 shows the NMR spectra of the polymer in example 1 before and after hydrolysis.

FIG. 3 shows the NMR spectra of the polymer in example 2 before and after hydrolysis.

FIG. 4 shows the NMR spectra of the polymer in example 3 before and after hydrolysis.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

The used materials are: 105 parts of tert-butyl 4-Bromobenzoate (tert-butyl-4-Bromobenzoate), 5000 parts of Cyclohexane (Cyclohexane) solvent, 140 parts of n-butyllithium (n-BuLi), 600 parts of Hexamethylcyclotrisiloxane (D3) monomer, 44 parts of dimethylmonochlorosilane (Chlorodimethyl silane) and 800 parts of trifluoroacetic acid (TFA) solution.

The synthetic route is as follows:

the synthesis steps are as follows:

(1) preparing a compound solution: 105 parts of tert-butyl 3-Bromobenzoate (tert-butyl-3-Bromobenzoate) compound dissolved in 2000 parts of Cyclohexane (Cyclohexane) solvent dried by a reagent purification apparatus was added to a two-necked reaction flask under vacuum to obtain a mixed solution.

(2) Preparation of an initiator: and (2) directly dropwise adding 140 parts of n-butyllithium (n-BuLi) into the mixed solution in the step (1) at 25 ℃ under a vacuum condition, and reacting for 2 hours to prepare the initiator.

(3) To a two-necked flask, 3000 parts of Cyclohexane (cyclohexoxane) solvent and 600 parts of Hexamethylcyclotrisiloxane (D3) monomer were added under vacuum. And (3) adding the initiator prepared in the step (2) into the system, and stirring and reacting for 16 hours at room temperature.

(4) 44 parts of dimethylchlorosilane (chlorodimethylchlorosilane) which has been distilled and purified in advance is added dropwise to the reaction system of (3) to carry out a coupling termination reaction, and after the addition is finished, the reaction is continued for 10 hours at room temperature.

(5) And (3) post-treatment: after the reaction is finished, carrying out reduced pressure distillation on the reaction liquid to obtain an oily transparent liquid crude product. The precipitation was then repeated 5 times in 30000 parts of methanol (MeOH). Finally, the pure product is obtained after filtration and drying, and the yield is more than 70 percent.

(6) Hydrolysis: the polymer obtained in the above (5 steps) was hydrolyzed in 800 parts of a trifluoroacetic acid (TFA) solution for 8 hours to obtain carboxyl-and dimethylsilyl end-functionalized polydimethylsiloxane.

Example 2

The materials used were: 110 parts of 5-bromothiophene-2-carboxylic acid methyl ester (5-Bromo-thiolene-2-carboxylic acid methyl ester), 160 parts of n-butyl lithium (n-BuLi), 4750 parts of Tetrahydrofuran (THF) solvent, 600 parts of Hexamethylcyclotrisiloxane (D3) monomer, 50 parts of dimethylmonochlorosilane (Chlorodimethylsilane), 1200 parts of 20% sodium hydroxide (NaOH) aqueous solution and 600 parts of ethanol solution.

The synthetic route is as follows:

the synthesis steps are as follows:

(1) preparing a compound solution: 110 parts of compound 5-bromothiophene-2-carboxylic acid methyl ester (5-Bromo-thiophene-2-carboxylic acid methyl ester) dissolved in Tetrahydrofuran (THF) solvent 2250 parts dried by a reagent purification apparatus were added to a two-necked reaction flask under vacuum to obtain a mixed solution.

(2) Preparation of an initiator: firstly, cooling the mixed solution of the step (1) to-78 ℃, then dropwise adding 160 parts of n-butyllithium (n-BuLi) into the mixed solution under a vacuum condition, and reacting for 2 hours at-78 ℃ to prepare the initiator.

(3) To a two-necked flask were added 2500 parts of Tetrahydrofuran (THF) solvent and 600 parts of Hexamethylcyclotrisiloxane (D3) monomer under vacuum, followed by cooling to-15 ℃. And (3) adding the initiator prepared in the step (2) into the system, and keeping the system to be stirred and reacted for 1 hour at the temperature of-15 ℃.

(4) 50 parts of dimethylchlorosilane (chlorodimethylchlorosilane) which has been distilled and purified in advance is added dropwise to the reaction system of the step (3) to carry out a coupling termination reaction, and after the addition is finished, the reaction is continued for 10 hours at room temperature.

(5) And (3) post-treatment: after the reaction is finished, carrying out reduced pressure distillation on the reaction liquid to obtain an oily transparent liquid crude product. The precipitation was then repeated 6 times in 25000 parts of methanol (MeOH). Finally, the pure product is obtained after filtration and drying, and the yield is more than 70 percent.

(6) Hydrolysis: and (3) hydrolyzing the polymer obtained in the step (5) in 1200 parts of 20% sodium hydroxide (NaOH) aqueous solution and 600 parts of ethanol solution for 13 hours to obtain the polydimethylsiloxane functionalized by carboxyl and dimethyl silicon end groups.

Example 3

The materials used were: hexamethyldisilazane (Hexamethyldisilazane)100 parts, n-butyllithium (n-BuLi)160 parts, Tetrahydrofuran (THF) solvent 2650 parts, Hexamethylcyclotrisiloxane (D3) monomer 600 parts, dimethylmonochlorosilane (Chlorodimethylsilane)66 parts, trifluoroacetic acid (TFA) solution 1200 parts.

The synthetic route is as follows:

the synthesis steps are as follows:

(1) preparing a compound solution: 100 parts of a compound Hexamethyldisilazane (Hexamethyldisilazane) dissolved in 2500 parts of a Tetrahydrofuran (THF) solvent dried by a reagent purification apparatus was added to a two-necked reaction flask under vacuum to obtain a mixed solution.

(2) Preparation of an initiator: firstly, cooling the mixed solution in the step (1) to-78 ℃, then dropwise adding 60 parts of n-butyllithium (n-BuLi) into the mixed solution under a vacuum condition, and reacting for 3 hours at-78 ℃ to prepare the initiator.

(3) To a two-necked flask were added 2000 parts of Tetrahydrofuran (THF) solvent and 600 parts of Hexamethylcyclotrisiloxane (D3) monomer under vacuum, followed by cooling to-10 ℃. And (3) adding the initiator prepared in the step (2) into the system, and keeping the system to be stirred and react for 2 hours at the temperature of minus 10 ℃.

(4) 66 parts of dimethylchlorosilane (chlorodimethylchlorosilane) which has been distilled and purified in advance is added dropwise to the reaction system of the step (3) to carry out a coupling termination reaction, and after the addition is finished, the reaction is continued at room temperature for 12 hours.

(5) And (3) post-treatment: after the reaction is finished, carrying out reduced pressure distillation on the reaction liquid to obtain an oily transparent liquid crude product. The precipitation was then repeated 8 times in 20000 parts of methanol (MeOH). Finally, the pure product is obtained after filtration and drying, and the yield is more than 70 percent.

(6) Hydrolysis: the polymer obtained in the above (5 steps) was hydrolyzed in 1200 parts of trifluoroacetic acid (TFA) solution for 12 hours to obtain carboxyl-and dimethylsilyl end-functionalized polydimethylsiloxane.

The polymers of examples 1-3 were analyzed by gel chromatography GPC for molecular weight measurements before and after hydrolysis, and the results of characterization are shown in Table 1:

TABLE 1

Table 1 shows GPC characterization results before and after hydrolysis of polymers of examples 1-3, FIG. 1 shows GPC test curves of polymers of example 2, and it can be seen from the results of Table 1 and FIG. 1 that the polymer obtained by anionic polymerization has a narrow distribution, which is consistent with the typical characteristics of anionic polymerization. Meanwhile, the molecular weight of the polymer is not changed greatly before and after hydrolysis, which shows that the polymer is relatively stable in the process of removing the end group protecting group.

FIGS. 2, 3 and 4 correspond to the hydrogen nuclear magnetic spectra before and after hydrolysis of the polymers in examples 1 to 3, respectively. From the nuclear magnetic results in FIGS. 2 and 3, it can be seen that the peak (-CH) of the methyl group signal of the terminal protecting group of the polymer before hydrolysis₃) The existence of the compound is compared, the methyl signal peak disappears after hydrolysis, the protective group is completely removed after hydrolysis, and the method can realize the synthesis of the polydimethylsiloxane with the end group of a carboxyl structure. Similarly, from the results of nuclear magnetism in FIG. 4, the methyl group (-CH) before and after hydrolysis was compared₃) The integral of the signal peak at the chemical shift shows that the integral value is reduced after hydrolysis, which indicates that the protective group is completely removed after hydrolysis, and further indicates that the method can realize the synthesis of the polydimethylsiloxane with the amino-group structure as the end group. It is emphasized that the present invention provides only the method for synthesizing the initiator structure design and the process for synthesizing the polymer, and the study of the properties of the polymer is not repeated herein.

The above description is not intended to limit the present invention, but rather, the present invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

Claims

1. A preparation method of end group functionalized polydimethylsiloxane is characterized by comprising the following specific steps:

(1) preparing a compound solution:

adding the compound A and a solvent into a two-mouth reaction bottle under a vacuum condition to obtain a mixed solution; here, the compound A is selected from hexamethyldisilazane, methyl 5-bromothiophene-2-carboxylate, tert-butyl 4-bromobenzoate, 4-bromo-N,N-one of bis (trimethylsilyl) aniline, methyl 5-bromo-2-furoate, tert-butyl 4-bromo-3-methylbenzoate and derivatives thereof; the solvent is one of tetrahydrofuran, cyclohexane, n-hexane or diethyl ether; wherein, the compound A accounts for 110 parts by weight, and the solvent accounts for 3000 parts by weight;

(2) the preparation of the initiator is divided into two methods:

(a) when the solvent used in the step (1) is tetrahydrofuran, the mixed solution is cooled to-78%^oC, then 60-160 parts of n-butyl lithium is dripped into the mixed solution under the vacuum condition, and the temperature is increased to-78 DEG^oReacting for 1-3 hours under C to prepare an initiator;

(b) when the solvent used in step (1) is other solvent, the solvent is at 20-30%^oC, directly dropwise adding 60-160 parts of n-butyl lithium into the mixed solution obtained in the step (1) under a vacuum condition, and reacting for 1-3 hours to prepare an initiator;

(3) adding 3000 parts of solvent 2000-S and 600 parts of hexamethylcyclotrisiloxane monomer into a two-mouth bottle under a vacuum condition; the solvent is the same as that in the step (1);

if tetrahydrofuran is selected as the reaction solvent, the temperature of the system is cooled to-10 to-15^oC, then adding the initiator prepared in the step (2-a) into the system, and keeping the system at-10 to-15 DEG C^oC, stirring and reacting for 1-2 hours;

if the reaction solvent is cyclohexane or other solvents, adding the initiator prepared in the step (2-b) into the system, and reacting for 12-16 hours at room temperature;

(4) 44-66 parts of dimethyl chlorosilane which is distilled and purified in advance are dripped into the reaction system in the step (3) to carry out coupling termination reaction, and after the dripping is finished, the reaction is continued for 8-12 hours at room temperature;

(5) and (3) post-treatment: after the reaction is finished, carrying out reduced pressure distillation on the reaction solution to obtain an oily transparent liquid crude product; then repeatedly carrying out precipitation for 5-8 times in 20000-30000 parts of methanol; filtering and drying to obtain a pure product, wherein the yield is more than 70%;

(6) hydrolysis: hydrolyzing the product obtained in the step (5) in 800-1200 parts of trifluoroacetic acid or 1600-20% sodium hydroxide aqueous solution with the concentration of 1000-800 parts of ethanol solution for 8-13 hours to obtain carboxyl, amido and dimethyl silicon end group functionalized polydimethylsiloxane;

wherein the components are calculated according to parts by mass.

2. The method of claim 1, wherein the solvents are tetrahydrofuran and cyclohexane.