CN115386075A

CN115386075A - Degradable branched-chain polycaprolactone and preparation method thereof

Info

Publication number: CN115386075A
Application number: CN202211197476.XA
Authority: CN
Inventors: 钟爱民
Original assignee: Yangzhou Polytechnic Institute
Current assignee: Yangzhou Polytechnic Institute
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2022-11-25
Anticipated expiration: 2042-09-29
Also published as: CN115386075B

Abstract

The scheme relates to a degradable branched polycaprolactone and a preparation method thereof, and the preparation method comprises the following steps: adding metered alpha-bromine-epsilon-caprolactone, 1, 4-butanediol and a catalyst into a reaction kettle, uniformly stirring, decompressing and dehydrating, and filling nitrogen to remove air in a system; adding metered phenyl glycidyl ether to carry out ring-opening polymerization reaction; after the reaction is finished, carrying out reduced pressure distillation and purification to obtain PCL-PGE; dissolving PCL-PGE in tetrahydrofuran, adding 2-methylene-1, 3-dioxepane and methacrylate monomers, adding a catalytic amount of CuBr/bpy, introducing nitrogen to remove air in the system, and heating to 90 ℃ to perform ATRP polymerization; after the reaction was completed, the product was precipitated in methanol. Compared with pure polycaprolactone, the degradable branched polycaprolactone prepared by the scheme has the advantages that the mechanical property is improved, the degradation rate is increased, and the degradable branched polycaprolactone is expected to be applied to the field of biomedicine.

Description

Degradable branched polycaprolactone and preparation method thereof

Technical Field

The invention relates to the field of degradable high polymer materials, in particular to a cocoa degradable branched polycaprolactone and a preparation method thereof.

Background

With the rapid development of social economy, the problems of resource shortage and environmental pollution are more serious. Plastic products were first developed to replace natural resources, and are cheap and widely available. However, non-degradable plastic articles place a great burden on the environment. Therefore, researchers are working on developing degradable polymer materials to solve this problem. At present, common degradable polymers are mainly polyester, and are easily decomposed in nature due to ester bonds which are easy to hydrolyze in molecular chains. Examples of the electrically conductive aliphatic polyester include Polyglycolide (PGA), polylactide (PLA), and Polycaprolactone (PCL).

PCL is a thermoplastic semi-crystalline polymer, has excellent biocompatibility and degradability, belongs to environment-friendly plastics, and has important application prospects in the fields of biomedicine and the like. However, PCL is a semi-crystalline polymer, and its practical application is limited by poor hydrophilicity, low mechanical strength, slow degradation rate, and the like.

Disclosure of Invention

Aiming at the defects in the prior art, the branched PCL is prepared based on caprolactone and 2-methylene-1, 3-dioxepane, the crystallinity is reduced, and the degradation rate is high.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of degradable branched polycaprolactone comprises the following steps:

s1: adding metered alpha-bromine-epsilon-caprolactone, 1, 4-butanediol and a catalyst into a reaction kettle, uniformly stirring, decompressing and dehydrating, and filling nitrogen to remove air in a system; adding metered phenyl glycidyl ether to carry out ring-opening polymerization reaction; after the reaction is finished, carrying out reduced pressure distillation and purification to obtain PCL-PGE;

s2: dissolving PCL-PGE in tetrahydrofuran, adding 2-methylene-1, 3-dioxepane and methacrylate monomers, adding a catalytic amount of CuBr/bpy, introducing nitrogen to remove air in the system, and heating to 90 ℃ to perform ATRP polymerization; after the reaction is finished, precipitating in methanol to obtain a product;

wherein the methacrylate monomer is cyclohexyl methacrylate monomer, and the structural formula is as follows:

further, in the step S1, the molar ratio of α -bromo- ∈ -caprolactone, 1, 4-butanediol, phenyl glycidyl ether, and the catalyst is 1.5 to 0.8; the catalyst is a 1.

Further, the reaction condition of the step S1 is 140-160 ℃ for 2-4 h.

Further, in the step S2, the molar ratio of PCL-PGE, 2-methylene-1, 3-dioxepane and methacrylate monomer is 1-50.

The scheme further provides the degradable branched polycaprolactone prepared by the preparation method.

Compared with the prior art, the invention has the beneficial effects that: according to the scheme, firstly, alpha-bromine-epsilon-caprolactone and phenyl glycidyl ether are used for preparing a random copolymer containing a CL chain segment, and a phenyl functional group can improve the rigidity of the polymer chain, so that the mechanical property of the polymer chain can be improved; and simultaneously, the steric hindrance effect among the molecular chains of the random copolymer is increased, the molecular chains are disordered, and the crystallinity is reduced. However, the dosage of the phenyl glycidyl ether cannot be excessive, the molar ratio of the phenyl glycidyl ether to the alpha-bromo-epsilon-caprolactone is optimally 0.4.

ATRP polymerization can be carried out through bromine at alpha position of caprolactone, and PCL side chain of the same type is grafted on the main chain; in the scheme, a monomer 2-methylene-1, 3-dioxepane capable of carrying out free radical polymerization is selected, a chain segment similar to PCL is formed after ring opening, the integral degradability of the polymer is kept, and in addition, a cyclohexyl methacrylate monomer is used as a comonomer, so that on one hand, the existence of cyclohexyl is also used for increasing the steric hindrance effect, and the space between macromolecular chains is enlarged to promote quick degradation; other polymer chains are inserted into the PCL chain segment, so that the crystallinity of the polymer can be effectively reduced, and the functionality of the polymer chain is increased by abundant functional groups; on the other hand, the pyrrolidone group is arranged at the para position of the cyclohexyl, so that the hydrophilic characteristic of the polymer is improved, the molecular chain after hydrolysis is broken to migrate to water molecules, and the hydrolysis is promoted; and due to good biodegradability, the biodegradable polylactic acid/polylactic acid copolymer is expected to be applied to the field of biomedicine.

Detailed Description

FIG. 1 is a graph showing the weight loss rate under hydrolysis conditions of each material in example 1 as a function of time.

FIG. 2 is the relationship between the weight loss rate and time under the enzymolysis condition of each material in example 1.

FIG. 3 is the relationship between the weight loss rate and time under the enzymolysis condition of each material in example 2.

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The raw materials used in this case are commercially available unless otherwise specified.

The preparation method of 2-methylene-1, 3-dioxepane refers to the research on the synthetic process of 2-methylene-1, 3-dioxepane, shandong chemical engineering, volume 46 in 2017.

The preparation route of the cyclohexyl methacrylate monomer is as follows:

example 1:

adding metered alpha-bromine-epsilon-caprolactone (Br-CL), 1, 4-Butanediol (BDO) and a catalyst into a reaction kettle, uniformly stirring, decompressing and dehydrating, and filling nitrogen to remove air in a system; adding metered Phenyl Glycidyl Ether (PGE), carrying out ring-opening polymerization reaction, and reacting for 2-4 h at 140-160 ℃; after the reaction is finished, carrying out reduced pressure distillation and purification to obtain PCL-PGE; wherein the molar ratio of Br-CL to BDO to PGE to the catalyst is 1. The following samples were obtained by changing the charge ratios of Br-CL, BDO and PGE.

TABLE 1

	Ratio of	Conv.％	Mn/g·mol ^-1	PDI	Tensile strength MPa
						PCL-PGE-1	1:0.5:0.4	90.4	7700	1.44	50.5
PCL-PGE-2	1:0.5:0.6	95.5	8100	1.21	52.6
						PCL-PGE-3	1:0.5:1	93.2	7900	1.68	54.1
PCL-PGE-4	1:0.5:1.2	90.6	8600	1.72	55.7
						PCL-PGE-5	1:0.5:1.6	88.4	8500	1.77	56.2

The degradability of the polymer is verified through hydrolysis and enzymolysis, and for convenience of experiments, the material is firstly prepared into a film, PCL-PGE is dried in vacuum to constant weight, a film with the thickness of 0.5mm is formed through hot pressing, and then the film is cut into a plurality of small blocks with the thickness of 1 multiplied by 2 cm.

The hydrolysis steps are as follows: preparing a buffer solution by adopting disodium hydrogen phosphate and dipotassium hydrogen phosphate, adding 10ml of the prepared buffer solution into five clean test tubes, respectively adding a sample of PCL-PGE-1-5 into the test tubes, carrying out hydrolysis under the condition of 40 ℃, sampling at regular intervals, measuring weight, calculating the weight loss rate, and drawing the graph 1.

The enzymolysis steps are as follows: a mixed solution of lipase and PBS (1 mg/mL) was prepared, and the weight loss ratios were plotted in FIG. 2 in the same manner as in the hydrolysis test in the other steps.

The molecular weight of the sample after the last enzymatic hydrolysis was measured and recorded in table 2.

TABLE 2

	PCL-PGE-1	PCL-PGE-2	PCL-PGE-3	PCL-PGE-4	PCL-PGE-5
						G/mol before degradation	7700	8100	7900	8600	8500
G/mol after enzymolysis	1100	1100	2000	2400	3100

Referring to FIGS. 1-2 in combination with tables 1-2, it can be seen that the PGE content during polymerization affects the polymer performance, and that increasing the PGE increases the tensile strength of the polymer, but the degradation rate and degradation rate are not positively correlated to the PGE content. PCL belongs to a semi-crystalline polymer, the degradation rate is generally slow, the distance between molecules is enlarged by inserting a polyether structure into a polymer chain, and the existence of phenyl further increases the steric hindrance, so that the degradation rate can be improved. However, when the content of PGE is too high, the degradation rate is decreased, and PGE is hardly degraded, and when the degradation is completed, a large molecular weight remains, and the degradation rate is low. Wherein, the comprehensive performance of the sample PCL-PGE-2 is optimal.

Example 2:

dissolving PCL-PGE-2 in tetrahydrofuran, adding 2-methylene-1, 3-dioxepane (MDO) and methacrylate monomer, adding catalytic amount of CuBr/bpy, introducing nitrogen to remove air in the system, and heating to 90 ℃ for ATRP polymerization; after the reaction is finished, precipitating in methanol to obtain a product; wherein, the molar ratio of PCL-PGE, MDO and methacrylate monomer is 1. Selecting PCL-PGE (Mn/g. Mol) ^-1 =8100 g/mol), the following final samples can be obtained by varying the feed ratio.

TABLE 3

	Ratio of	Mn/g·mol ^-1	Tensile strength Mpa
				PCL-PGE-2-1	1:50:50	25600	45.5
PCL-PGE-2-2	1:60:40	22900	43.3
				PCL-PGE-2-3	1:70:30	20500	41.2
PCL-PGE-2-4	1:80:20	19500	40.1
				PCL-PGE-2-5	1:100:0	14900	34.2

The enzymatic hydrolysis procedure was as described above, with the enzymatic hydrolysis rates shown in FIG. 3.

By grafting the polymer chain of MDO and cyclohexyl methacrylate monomer at the branched chain, the tensile strength of the polymer is reduced, but the degradation rate of the polymer is further promoted. Compared with PCL-PGE-2 and PCL-PGE-2-1-5, the degradation rate is slower in the initial degradation period (0-5 h) because the molecular weight is increased and the molecular chain is long after ATRP polymerization; the rate in the middle degradation period is obviously improved, the hydrophilic groups promote the migration of water molecules to the interior of the material, the degradation degree is obviously increased, the rate is reduced to 15h, and the weight loss rate approaches to balance. The ratio of the fed monomers is changed, and when only MDO monomer is contained in the reaction system, the molecular weight is lower. As the crystallinity of the PCL chain formed after the MDO ring opening is low, the degradation rate is higher than that of the PCL chain formed after the pure caprolactone ring opening, the degradation rate and the degradation completion degree (weight loss rate) of the finally obtained material PCL-PGE-2-5 are higher than those of the PCL-PGE-2-4, but the tensile strength is also the lowest, and comprehensively, the PCL-PGE-2 has the best performance, namely when the charge ratio of the MDO to the cyclohexyl methacrylate monomer is 60.

While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details without departing from the general concept defined by the claims and the scope of equivalents.

Claims

1. A preparation method of degradable branched polycaprolactone is characterized by comprising the following steps:

2. the method for preparing a degradable branched polycaprolactone according to claim 1 wherein in step S1, the molar ratio of α -bromo-e-caprolactone, 1, 4-butanediol, phenyl glycidyl ether and catalyst is 1; the catalyst is a 1.

3. The method for preparing degradable branched polycaprolactone according to claim 1, wherein the reaction conditions of step S1 are 140-160 ℃ for 2-4 h.

4. The method for preparing degradable branched polycaprolactone according to claim 1, wherein in the step S2, the molar ratio of PCL-PGE to 2-methylene-1, 3-dioxepane to methacrylate monomer is 1.

5. A degradable branched polycaprolactone obtained by the process according to any one of claims 1 to 4.