CN111763324A - A kind of triblock copolymer based on anionic ring-opening polymerization mechanism and preparation method - Google Patents

Abstract

The invention relates to a polycaprolactam-polydimethylsiloxane-polycaprolactam (PLC-PDMS-PLC) triblock copolymer based on an anion ring opening polymerization mechanism (ROP). The hydroxyl-terminated polydimethylsiloxane reacts with caprolactam to generate the triblock copolymer with controllable molecular weight and crosslinking density. The hydroxyl-terminated polydimethylsiloxane chain segment in the PLC-PDMS-PLC triblock copolymer is incompatible with epoxy resin, the polycaprolactam chain segment has good compatibility with the epoxy resin, and an amide group in the polycaprolactam structure can perform a crosslinking reaction with the epoxy resin to form a three-dimensional structure. Therefore, the polycaprolactam-polydimethylsiloxane-polycaprolactam triblock copolymer is introduced into the epoxy resin to form a nano split-phase structure, has a toughening effect, and has wide application in the fields of aerospace, transportation, buildings and the like.

Description

A kind of triblock copolymer based on anionic ring-opening polymerization mechanism and preparation method

technical field

The invention relates to a preparation method of a polycaprolactam-polydimethylsiloxane-polycaprolactam (PLC-PDMS-PLC) triblock copolymer.

Background technique

Anionic ring-opening polymerization (ROP) is a reaction in which the monomer forms an anionic initiation center by an anionic initiator, and the chain grows through a chain reaction mechanism, and the end group of the formed chain has a negative charge. In the presence of strong bases, the initiator and transition metal complexes are halogen atom carriers, and through redox reactions, a reversible dynamic equilibrium is established between the active species and the dormant species, thereby realizing the control of the polymerization reaction. It has attracted wide attention due to its advantages of a wide variety of applicable monomers, the ability to synthesize polymers of uniform molecular weight, and its suitability for various industrial polymerization methods. It also has broad application prospects in modified thermosetting resins. PLC-PDMS-PLC is a new type of triblock copolymer, in which the Si-O bond provided by polydimethylsiloxane (PDMS) can improve the heat resistance and mechanical properties of the system; the introduction of polycaprolactam (PLC) The number of hydrogen bonds and amide groups can be increased to improve the toughness of the system, while the amide bonds react with epoxy groups in the epoxy resin, thereby increasing the crosslinking density. By controlling the ratio of PDMS to amide segments, its compatibility in the matrix is controlled, a nano-phase-separated structure is formed, and the system has good comprehensive performance. Therefore, PLC-PDMS-PLC triblock copolymer has better performance than pure caprolactam and PDMS. It utilizes the mechanism of ring-opening polymerization, which is convenient to control the reaction rate and degree of reaction. The operation is simple, and the conditions are mild and safe.

SUMMARY OF THE INVENTION

1. The purpose of the present invention is to provide a PLC-PDMS-PLC triblock copolymer with better heat resistance and mechanical properties, and Fig. 1 is the structural formula diagram of the polymer, wherein: m, n are ≥ 1. Integer.

2. The present invention provides a polymer with a completely new structure, the repeating unit of which contains at least one Si-O structure. By adjusting the ratio of the amount of PDMS to ε-caprolactam to 1:(10-100), the molecular weight, molecular structure and nano-phase-separation structure of the polymer in the resin can be easily controlled, so as to achieve the polymer The goal of performance tunability.

3. the present invention provides a kind of preparation method of PLC-PDMS-PLC triblock copolymer, and its steps are as follows:

(1) Activation of caprolactam monomer: ε-caprolactam and sodium hydroxide are mixed in the amount of substance (3～4): 1, keep the reaction system in a vacuum state, and heat and dissolve ε-caprolactam monomer 2 at 110℃～120℃ After ~3 hours, the water was sufficiently removed and activated to form an activated caprolactam monomer, the reaction scheme of which is shown in FIG. 2 .

(2) Preparation of PLC-PDMS-PLC triblock copolymer: under the protection of inert gas, hydroxyl-terminated polydimethylsiloxane (HO-PDMS-OH) was added to the activated caprolactam monomer, and the substance was Quantity 1: (10-100) mixed reaction was carried out for 3-5 hours, the product was cooled to room temperature and washed with ethanol until neutral, and dried in an oven to obtain PLC-PDMS-PLC triblock copolymers with different molecular weights. Figure 3 is a reaction diagram of the triblock copolymer prepared according to the above description.

Among them: Figure 4 is the structural diagram of HO-PDMS-OH

4. The present invention starts from the molecular structure design, uses PDMS as the segment, and the Si-O bond provided by it helps to improve the heat resistance and mechanical properties of the system; the terminal hydroxyl group causes the caprolactam to grow into an amide segment, which provides The amide group helps to improve the compatibility of the block copolymer with the epoxy resin system and improve the toughness of the system.

5. The present invention starts from the segment compatibility design, the PDMS segment is insoluble in epoxy resin, and the caprolactam segment containing an amide group has good compatibility with the epoxy resin matrix, so the prepared PLC-PDMS-PLC three The block copolymer forms a nano-phase-separated structure in the epoxy resin matrix, and the phase-separated structure also changes with the content of the block copolymer.

Specific embodiments:

In order to facilitate a further understanding of the present invention, the following examples illustrate more specific details, but the embodiments of the present invention are not limited thereto.

Example 1:

Weigh 27.2g of ε-caprolactam and 0.6g of sodium hydroxide into a three-necked round-bottomed flask, mix and stir, remove moisture and air in a vacuum system device, and heat to 110 °C while maintaining a continuous vacuum state, stop pumping after 2 hours The vacuum was changed to a nitrogen atmosphere, 20 g of HO-PDMS-OH was weighed and added to the reaction system, the reaction was continued at 110°C, the reaction was stopped after 4 hours, and the product was poured out while hot. After the product was cooled to a solid at room temperature, it was taken out, the obtained crude product was washed in ethanol to neutrality, and placed in a vacuum oven at room temperature for 24 hours to obtain a dry solid white powder.

1 g of this product was added to 20 g of E-51 type epoxy resin, at 800 °C in a nitrogen atmosphere, T _d5 (the temperature at which the mass loss was 5wt%) was 361.3 °C, and _Tmax (the temperature at which the mass loss rate was the largest) was 404.0℃, the mechanical properties of the modified system were tested, and its K _IC was 1.49MPa·m ^1/2 .

Example 2:

Weigh 108.4g of ε-caprolactam and 0.6g of sodium hydroxide into a three-necked round-bottomed flask, mix and stir, remove moisture and air in a vacuum system device, and heat to 110°C while maintaining a continuous vacuum state, stop pumping after 2 hours The vacuum was changed to nitrogen atmosphere, 20g of OH-PDMS-OH was weighed and added to the reaction system, the reaction was continued at 110°C, the reaction was stopped after 4 hours, and the product was poured out while hot. After the product was cooled to a solid at room temperature, it was taken out, the obtained crude product was washed in ethanol to neutrality, and placed under vacuum at room temperature for 24 hours to obtain a dry solid white powder.

1 g of this product was added to 20 g of E-51 type epoxy resin at 800°C in a nitrogen atmosphere with a T _d5 of 280.4°C and a T _max of 408.3°C. The mechanical properties of the modified system were tested, and its K _IC was 2.20MPa·m ^1/2 .

Example 3:

Weigh 43.52g of ε-caprolactam and 0.6g of sodium hydroxide into a three-necked round-bottomed flask, mix and stir, remove moisture and air in a vacuum system device, and heat to 110 ° C while maintaining a continuous vacuum state, stop after 2 hours The vacuum was changed to nitrogen atmosphere, and 20 g of HO-PDMS-OH was weighed and added to the reaction system, and the reaction was continued at 110 ° C. After 4 hours, the reaction was stopped, and the product was poured out while hot. After the product was cooled to a solid at room temperature, it was taken out, the obtained crude product was washed in ethanol to neutrality, and placed under vacuum at room temperature for 24 hours to obtain a dry solid white powder.

1 g of this product was added to 20 g of AG-80 type epoxy resin at 800°C in a nitrogen atmosphere, with a T _d5 of 410°C and a T _max of 461°C. The mechanical properties of the modified system were tested, and its K _IC was 1.25MPa·m ^1/2 .

Example 4:

Weigh 81.6g of ε-caprolactam and 0.6g of sodium hydroxide into a three-neck round-bottomed flask, mix and stir, remove moisture and air in a vacuum system device, and heat to 110°C while maintaining a continuous vacuum state, stop pumping after 2 hours The vacuum was changed to nitrogen atmosphere, 20g of OH-PDMS-OH was weighed and added to the reaction system, the reaction was continued at 110°C, the reaction was stopped after 4 hours, and the product was poured out while hot. After the product was cooled to a solid at room temperature, it was taken out, the obtained crude product was washed in ethanol to neutrality, and placed under vacuum at room temperature for 24 hours to obtain a dry solid white powder.

1 g of this product was added to 20 g of E-51 type epoxy resin at 800°C in a nitrogen atmosphere with a T _d5 of 401°C and a T _max of 445.0°C. The mechanical properties of the modified system were tested, and its K _IC was 1.32MPa·m ^1/2 .

The above are only specific examples of the embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements can also be made, and these improvements should also be regarded as It is the protection scope of the present invention.

Claims (5)

1. The invention prepares a polycaprolactam-polydimethylsiloxane-polycaprolactam (PLC-PDMS-PLC) triblock copolymer.

2. The method of preparing the PLC-PDMS-PLC triblock copolymer of claim 1, comprising the steps of:

(1) caprolactam monomer activation: sodium hydroxide and caprolactam monomer are added into the device at room temperature, and the vacuum system device is used to remove moisture and air under the heating state, so that the caprolactam monomer is activated.

(2) Preparing a PLC-PDMS-PLC triblock copolymer: under the protection of inert gas, adding hydroxy polydimethylsiloxane (HO-PDMS-OH) into the activator in the first step, after the reaction is completed, washing the obtained crude product in ethanol to be neutral and drying to finally obtain the PLC-PDMS-PLC triblock copolymer with an amido repeating unit and a siloxane repeating unit.

3. The process of claim 2, wherein the molecular weight of HO-PDMS-OH is 800g/mol to 2000g/mol, the reaction temperature is 80 to 110 ℃, the reaction time is 2 to 4 hours, and the molar ratio of sodium hydroxide to HO-PDMS-OH is 1: (1-3).

4. The PLC-PDMS-PLC triblock copolymer prepared according to claim 2, characterized in that: the molar ratio of HO-PDMS-OH to caprolactam is 1: (10-100), the reaction temperature is 110-130 ℃, and the reaction time is 3-5 hours.

5. The PLC-PDMS-PLC triblock copolymer prepared according to claim 2 is added in the epoxy resin in an amount ranging from 1 to 50 wt%. The epoxy resin is glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, glycidyl ether type epoxy resin, alicyclic epoxy resin and aliphatic epoxy resin.

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