阅读说明：本技术 一种内应力可视化的半互穿网络型形状记忆复合物及其制备方法 (Internal stress visualized semi-interpenetrating network type shape memory compound and preparation method thereof ) 是由 王倡春 荆佳杰 李恒 张珂 李书航 侍楠 王倩楠 胡思凡 于 2019-10-23 设计创作，主要内容包括：本发明公开了一种内应力可视化的新型水驱动半互穿网络形状记忆材料及其制备方法。该材料由聚乙二醇与聚丙烯酸组成的具有形状记忆功能的复合材料。当该材料在外力下变形(弯曲、扭曲等)、撤销外力后,材料因自身弹性,回复原始形状；但当材料吸水后,材料在外力作用后产生的内应力的作用下,产生形变(称为内应力赋形,材料处于临时形状),当烘干后,材料回复原始形状。该材料在吸水后,材料会根据所受外力自动产生弯曲或扭曲形变；使内应力可视化。该材料原料价廉、制备简单,易于大批量生产。(The invention discloses a novel internal stress visualized water-driven semi-interpenetrating network shape memory material and a preparation method thereof. The material is a composite material with a shape memory function, which is composed of polyethylene glycol and polyacrylic acid. When the material is deformed (bent, twisted and the like) under external force and the external force is removed, the material returns to the original shape due to the elasticity of the material; however, after the material absorbs water, the material is deformed (called internal stress forming, the material is in a temporary shape) under the action of internal stress generated after the action of external force, and after being dried, the material returns to the original shape. After the material absorbs water, the material can automatically generate bending or twisting deformation according to the external force; internal stress is visualized. The material has the advantages of low cost of raw materials, simple preparation and easy mass production.)

1. An internal stress visualized water-driven semi-interpenetrating network type shape memory composite is characterized in that polyacrylic acid (PAA) is selected as a matrix material, and polyethylene glycol (with the molecular weight of 4000-12000) is selected as a modification material.

2. The internal stress visualized water driven semi-interpenetrating network type shape memory composite of claim 1, wherein the material is deformable under internal stress after absorbing water when the mass ratio of polyethylene glycol (PEG) and Acrylic Acid (AA) is 1: 6 to 1: 3; after drying, the material can completely return to the original shape.

3. The internal stress visualized water driven semi-interpenetrating network type shape memory composite of claim 1, wherein the material spontaneously deforms upon absorbing water to visualize internal stress.

4. The internal stress visualized water driven semi-interpenetrating network type shape memory composite of claim 1, wherein the shape memory recovery process comprises the steps of:

1) the strip-shaped compound is deformed (such as bending 90 degrees, twisting 90 degrees or twisting 180 degrees) under the stress at 70 ℃ to form a temporary shape;

2) when the sample in the temporary form absorbs water, the material returns to the original flat state.

5. The internal stress visualized water driven semi-interpenetrating network type shape memory composite of claim 1, characterized in that the internal stress visualization process comprises the steps of:

1) flat, elongated samples, which deform under the action of external forces (e.g.: twist, bend, etc.) and held for 5 seconds; after the external force is removed, the sample returns to a straight state due to the elasticity of the sample;

2) the flat sample is placed in water and the sample is automatically deformed (e.g.: a twisted shape, a bent shape, etc.);

3) the deformed sample is dried and then changed back to the original straight state.

6. The internal stress visualized water driven semi-interpenetrating network type shape memory composite of claim 1, characterized in that its preparation process comprises the following:

1) weighing equal volume of acrylic acid and deionized water or distilled water, and uniformly mixing in a beaker;

2) slowly adding a proper amount of KOH into the acrylic acid solution cooled by the ice water, and continuously stirring for heat dissipation to ensure that the neutralization degree of the acrylic acid reaches 80 percent;

3) after the solution is cooled to room temperature, adding 0.02-0.04 wt% of cross-linking agent N, N' -methylene bisacrylamide, and preserving heat for 5min in a water bath kettle at 70 ℃;

4) adding 33-50 wt% of PEG solution into acrylic acid solution, adding 0.45-0.5 wt% of ammonium persulfate, and starting stirring;

5) when the solution begins to become viscous, the solution is poured into a mould and dried in a vacuum drying oven at 70 ℃ to obtain the internal stress visualized water-driven semi-interpenetrating network type shape memory compound.

Technical Field

The invention relates to the field of high-performance functional composite materials, in particular to an internal stress visualized water-driven semi-interpenetrating network type shape memory compound and a preparation method thereof.

Background

Shape memory materials are a class of smart materials that can recover the original shape of the material under certain external conditions, such as heat, solvent, humidity, force, pH, magnetic field, and the like. Shape memory polymers have the characteristics of large deformable quantity, easiness in shaping, easiness in processing, light weight, low price and the like, and are increasingly paid more attention. The rapid development in recent years, and the emergence of emerging products, make the application fields thereof cover various fields of daily life.

Polyethylene glycol (PEG) is a water-soluble polymer, and is widely used in various pharmaceutical preparations such as injections, topical preparations, ophthalmic preparations, oral preparations, and rectal preparations. When the molecular weight of the polyethylene glycol is more than 4000, the polyethylene glycol is safe to human bodies, and the finished product has physiological inertia, mildness, lubricity and the like.

Acrylic Acid (AA) is a very fast polymerizing vinylic monomer that is miscible with water, alcohols, ethers and chloroform and can be prepared from propylene. Acrylic acid is one of important raw materials for preparing water-soluble polymers, and can be grafted and copolymerized with starch to prepare the super water absorbent. Since polyacrylic acid gel has a large number of hydrophilic groups, acrylic acid is used to prepare super absorbent resin.

The invention mixes polyethylene glycol (PEG) and Acrylic Acid (AA) to prepare the PAA/PEG compound with a semi-interpenetrating network structure by a chemical crosslinking method, and the shape memory performance and the elasticity of the PAA/PEG compound are constantly improved along with the increase of the using amount of the acrylic acid.

Internal stress refers to the stress that remains inside the object when the external load is removed. The reason for this is that the volume change inside the material is not uniform, and the detection methods in the market at present mainly include polarized light detection, temperature shock detection, polar solvent immersion method, etc., but most of these methods require external precision instruments for detection, and some methods also cause irreparable damage to the material. The composite can quickly complete internal stress display in deionized water without external instruments and damaging the material.

Reference documents:

[1] preparation and drug controlled release behavior study of a chitosan/polyethylene glycol/polyacrylic acid composite hydrogel [ J ] chemical study and application, 2017, 29 (04): 446-452.

[2] Liu Bin, Sun Farfli, Wu Huaping, Yang Xiutre, a gem, Nayebare Kakwara Propper, Xujunting. construction of drug-loaded polyacrylic acid/polyethylene glycol semi-interpenetrating polymer networks in wood in situ and its properties [ J ] forestry science, 2016, 52 (11): 134-141.

[3] Li glu, zhangguang, chenjianwei, study of moisture sensitive shape memory knitted fabric [ J ]. academic press of functional polymers, 2004, 17 (3): 401-405, 410.

[4] "Zhuzhang zhao", Shiwenwei, Liuhuanju Shu ", et al. 152-158.

Disclosure of Invention

In order to prepare the internal stress visualized water-driven semi-interpenetrating network type shape memory material, the invention utilizes polyacrylic acid and polyethylene glycol to form a semi-interpenetrating network structure, so that the shape memory material becomes a shape memory compound with certain structural strength. Besides being bound by ion-dipole force, the polyethylene glycol long-chain molecule and the polyacrylic acid network can be connected by hydrogen bond. Therefore, the compound has better water-driven shape memory performance and better toughness and internal stress display process performance. The compound has low cost of raw materials and wide source.

The PEG/PAA compound provided by the invention has a shape memory function by utilizing the unfolding of the coiled long chain after a PEG molecular chain meets water, the recovery of the PEG molecular chain after dehydration and the swelling effect of a polyacrylic acid network.

The PEG/PAA compound has an internal stress display function because: after the material absorbs water, the material deforms (temporary form given by internal stress) under the action of the internal stress generated by the action of external force, so that the internal stress is visualized.

The invention provides a preparation method of an internal stress visualized water-driven semi-interpenetrating network type shape memory compound, which comprises the following steps:

1) weighing equal volume of acrylic acid and distilled water, and uniformly mixing in a beaker;

2) slowly adding a proper amount of KOH into the acrylic acid solution cooled by the ice water, and continuously stirring for heat dissipation to ensure that the neutralization degree of the acrylic acid reaches 80 percent;

3) after the solution is cooled to room temperature, adding 0.02-0.04 wt% of cross-linking agent N, N' -methylene bisacrylamide, and preserving heat for 5min in a water bath kettle at 70 ℃;

4) adding 33-50 wt% of PEG solution into acrylic acid solution, adding 0.45-0.50 wt% of ammonium persulfate, and starting stirring;

5) when the solution begins to become viscous, the solution is poured into a mould and dried in a vacuum drying oven at 70 ℃ to obtain the internal stress visualized water-driven semi-interpenetrating network type shape memory compound.

The invention provides a shape memory process, an internal stress display process and related mechanical properties of an internal stress visualized water-driven semi-interpenetrating network type shape memory compound prepared by the method.

Wherein the shape memory recovery process comprises the following steps:

1) the strip-shaped compound is deformed (such as bending 90 degrees, twisting 90 degrees or twisting 180 degrees) under the stress at 70 ℃ to form a temporary shape;

2) when the sample in the temporary form absorbs water, the material returns to the original flat state again.

The process of displaying internal stress comprises the following steps:

1) flat, elongated samples, which deform under the action of external forces (e.g.: twist, bend, etc.) and held for 5 seconds; after the external force is removed, the sample returns to a straight state due to elasticity;

2) the flat sample is placed in water and the sample is automatically deformed (e.g.: a twisted shape, a bent shape, etc.);

3) the deformed sample is dried and then changed back to the original straight state.

Drawings

FIG. 1 is a schematic diagram of the preparation of the inventive complex

FIG. 2 is a schematic of the microstructure of the inventive composite

FIG. 3 is a diagram of the process of shape memory recovery of the inventive composite (mass ratio 1: 5) after 180 DEG twisting

FIG. 4 is a graph showing the internal stress process of the inventive composite (mass ratio 1: 5) twisted by 180 °

FIG. 5 is a stress-strain curve of the inventive composite (mass ratio of 1: 6, 1: 5, 1: 3)

Detailed Description

For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings.