CN113121847B

CN113121847B - Preparation method and application of sliding material based on hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide

Info

Publication number: CN113121847B
Application number: CN202110416227.4A
Authority: CN
Inventors: 刘育; 王帅鹏; 陈湧; 王丽华
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2021-04-19
Filing date: 2021-04-19
Publication date: 2022-04-01
Anticipated expiration: 2041-04-19
Also published as: CN113121847A

Abstract

Based on hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide (Hy alpha CD-ACA-PEG)₂₀₀₀₀-ACA) sliding material and its use. The preparation method of the material is mainly characterized in that a quasi-rotaxane cross-linking agent formed by hydroxypropyl alpha-cyclodextrin and acrylamide-polyethylene glycol-acrylamide and an acrylamide aqueous solution are subjected to photoinitiated cross-linking to form a hydrogel polymer, and then the hydrogel polymer is immersed into a sodium hydroxide aqueous solution containing a certain amount of 1, 4-butanediol glycidyl ether to obtain the polymer material of the slip ring hydrogel, which is easy to prepare and high in elasticity. The invention has the advantages that: the sliding material of the present invention has high elasticity, excellent fatigue resistance and reusability. The material has good viscosity, does not need to add any adhesive, and can be easily adhered to the skin. In addition, the resulting polymer material is electrically conductive and exhibits a significant change in electrical resistance upon stretching. The polymer has wide application prospect in the aspect of wearable strain sensors.

Description

Preparation method and application of sliding material based on hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide

Technical Field

The invention belongs to the field of polymer gel, and relates to preparation of a high-elasticity stretchable material. In particular to a forming process of hydroxypropyl alpha-cyclodextrin and acrylamide-polyethylene glycol-acrylamide pseudorotaxane, a step of forming end-capped polyrotaxane by photoinitiation with acrylamide, and application thereof in the field of human body interactive wearable sensors.

Background

Hydrogels are widely used in various fields, such as tissue engineering, delivery of drugs and proteins, cosmetics, and absorbents for waste recovery. Many applications place increasingly higher demands on the mechanical properties of hydrogels. However, conventional chemical polymer gels can only be broken by uniaxial stretching 1.2-1.5 times because of their relatively weak mechanical properties, because their network hardly disperses internal stresses. Thus, scientists developed a series of methods to improve the mechanical properties of polymer hydrogels. One of the most common strategies is to introduce non-covalent forces into the polymer matrix, which can allow the network to easily dissipate mechanical energy, such as hydrogen bonding, host-guest interactions, hydrophobic interactions, and the like. Although these non-covalently crosslinked hydrogels (referred to as physical hydrogels) tend to achieve high elasticity, they may dissolve during long-term use and have greater hysteresis during repeated expansion and contraction. Another strategy is to optimize the polymer network structure of chemically crosslinked hydrogels to facilitate the dispersion of internal stresses. A very typical example is a double network gel, where two polymer networks with different chain lengths are interpenetrating and the short chain polymer network breaks due to energy dissipation, but the long chain polymer network remains highly elastic, which has proven to have excellent mechanical properties and good stability, superior to physical polymer hydrogels. However, one serious problem we have to face is that the preparation of double-network gel hydrogels is often complicated, greatly limiting their practical applications.

Recently, a slip ring gel consisting of a polyrotaxane crosslinked polymer network and a high solvent content has been widely recognized as an highly elastic chemically crosslinked gel in which "rings" and polymer chains can freely slide on a shaft, thereby providing the gel network with excellent internal stress dispersion capability. However, like in the case of the double-network gel, the synthesis of the slip ring hydrogel is also extremely difficult, mainly because the synthesis efficiency of polyrotaxane is low. Taking the synthesis example of the commonly used PEG-alpha CD polyrotaxane, the yield is usually 5% -10%. In addition, a dialysis operation must be used in this process, which is very disadvantageous for industrialization.

Disclosure of Invention

The invention aims to solve the problems that the preparation method of the traditional chemical polymer hydrogel is complex generally and the practical application of the traditional chemical polymer hydrogel is greatly limited, and provides a novel high-elasticity slip ring hydrogel and a preparation method thereof. The slip ring material has excellent mechanical properties and has wide application prospect in the field of wearable strain sensors.

The technical scheme of the invention is as follows:

based on hydroxypropyl alpha-cyclodextrin and acrylamide-polyethylene glycol-acrylamide (Hy alpha CD-ACA-PEG)₂₀₀₀₀ACA) from the monomers hydroxypropyl α -cyclodextrin (Hy α CD) and acrylamide-polyethylene glycol-acrylamide (ACA-PEG)₂₀₀₀₀-ACA). Wherein the structures of the monomers are respectively as follows:

sliding material polymer Hy alpha CD-ACA-PEG₂₀₀₀₀The structure of ACA is shown in fig. 7. The sliding material is prepared by firstly allowing ACA-PEG to be in aqueous solution₂₀₀₀₀ACA forms pseudorotaxanes with Hy α CD due to ACA-PEG₂₀₀₀₀The ACA monomer has a double bond at both ends, thus ACA-PEG₂₀₀₀₀the-ACA and Hy alpha CD pseudorotaxane can be used as a cross-linking agent to be mixed with an acrylamide solution, a photoinitiator is added, a three-dimensional network structure is formed under the photoinitiation condition, and then sodium hydroxide strong base is added to enable the ACA-PEG to be in a state of adding₂₀₀₀₀-reacting Hy α CD with 1, 4-butanediol glycidyl ether in the ACA molecular chain, thereby bridging the Hy α CDs with 1, 4-butanediol glycidyl ether, thereby forming the sliding material.

The invention further discloses a composition based on hydroxypropyl alpha-cyclodextrin and acrylamide-polyethylene glycol-acrylamide (Hy alpha CD-ACA-PEG)₂₀₀₀₀-ACA) sliding material, comprising the following steps:

(1) monomeric ACA-PEG₂₀₀₀₀-synthesis of ACA;

first, 1-10g, preferably 10g (5 x 10)^-4mol) dried polyethylene glycol (PEG, 20000) dissolved in 30-120mL, preferably 120mL, of dry CH₂Cl₂Then 12-60mL, preferably 50mL, of pyridine are added to the mixture and 80-240mg, preferably 240mg (1.26 x 10) are added dropwise^-3mol) toTosyl chloride (TsCl), stirred at room temperature overnight; the mixture was washed with 2.8-3.2moL/mL HCl and to the organic phase (water in hydrochloric acid, all remaining organic phases) was added an excess of solid sodium bicarbonate and stirred until no air bubbles were found.

Then, filtering, drying the filtrate, recrystallizing with THF, then removing the solvent, dissolving the product in 145-160mL ammonia water, and stirring for 48-60 h; the product is used with 80-120mL CH₂Cl₂Extracted and then passed through 10-50g MgSO₄Drying and filtering; then, the product is dissolved in 80 to 120mL of anhydrous dichloromethane, triethylamine in 5 to 10 times of the molar equivalent of the product and acryloyl chloride in 5 to 10 times of the molar equivalent of the product are added, and the mixture is subjected to N reaction at room temperature₂Reacting for more than 48h under the protection of gas, and finally separating and purifying to obtain ACA-PEG₂₀₀₀₀-ACA。

(2) Polymer Hy alpha CD-ACA-PEG₂₀₀₀₀-synthesis of ACA hydrogel, by the following method:

195-205mg of ACA-PEG₂₀₀₀₀Dissolving ACA in 9.5-10.5mL deionized water, and adding the solution according to ACA-PEG₂₀₀₀₀-ACA: adding Hy alpha CD in the ratio of 1:0,1:5 or 1:10, ultrasonic treating, and standing at room temperature to obtain Hy alpha CD-ACA-PEG₂₀₀₀₀-an ACA pseudorotaxane cross-linker near-transparent suspension;

shaking 0.9-1.1mL Hy alpha CD-ACA-PEG₂₀₀₀₀Mixing the nearly transparent suspension of the-ACA pseudorotaxane cross-linking agent with 2.8-3.2mL of acrylamide aqueous solution with the concentration of 280-320mg/mL, and adding I₂₉₅₉The photoinitiator transfers the mixed solution to a polytetrafluoroethylene template after the system is clarified and transparent by simple shaking, and covers a glass slide; then irradiating the mixture with 365nm ultraviolet light to obtain Hy alpha CD-ACA-PEG₂₀₀₀₀-ACA hydrogel; then, the polymer is immersed into a sodium hydroxide aqueous solution containing 5 to 20 mass percent of 1, 4-butanediol glycidyl ether to form the slip ring hydrogel polymer.

The invention further discloses different ACA-PEG₂₀₀₀₀-ACA: high elasticity and excellent fatigue resistance of Hy alpha CD proportional polymer. The method comprises the following steps:

(1) different ACA-PEG₂₀₀₀₀-ACA: hy α CD ratioExample Polymer materials

Prepared Hy alpha CD-ACA-PEG₂₀₀₀₀ACA polymers have a high elasticity in all rotaxane ratios, and in the ratios chosen, the gel strength and elasticity under certain conditions increase with the addition of cyclodextrin, the higher the cyclodextrin content, the greater the elasticity, but the greater the strain loss at break.

(2) Different Hy alpha CD-ACA-PEG₂₀₀₀₀-ACA material

Prepared polymer Hy alpha CD-ACA-PEG₂₀₀₀₀Dissolving 0.2M CaCl in the pre-reaction solution₂And the other operations are unchanged. The elasticity of the polymer material is slightly reduced, the energy to break is much increased, and the tensile strength is greater. Overall, CaCl was added₂The mechanical property of the material is enhanced.

Finally, the invention also discloses application of the sliding material based on hydroxypropyl alpha-cyclodextrin and acrylamide-polyethylene glycol-acrylamide (Hy alpha CD-ACA-PEG20000-ACA) prepared by the method in the aspect of manufacturing a wearable strain sensor, and the strain sensor can respond to tension, pressure, breathing and the like.

The invention has the advantages and beneficial effects that:

hy alpha CD-ACA-PEG in the invention₂₀₀₀₀the-ACA hydrogel polymer was synthesized in high purity by a simple two-step reaction, first, Hy α CD-ACA-PEG₂₀₀₀₀ACA readily forms pseudorotaxanes in water by host-guest interaction, and secondly, a quantity of pseudorotaxane solution is transferred to an acrylamide solution, in water a small amount of I₂₉₅₉In the presence of (a), a polyrotaxane is produced by a simple photo-initiated polymerization reaction. Next, the polyrotaxane is immersed in a sodium hydroxide solution of 1, 4-butanediol glycidyl ether. Thus, a slip ring hydrogel having excellent mechanical properties is easily formed. Importantly, such hydrogels need only be doped with 0.2M CaCl₂(can improve the ionic conductivity), namely can be used for constructing a wearable strain sensor with high performance.

The designed sliding polymer hydrogel material has high elasticity and good recovery performance, can be repeatedly used and has high preparation yield. After the gel is stretched, the resistance change value is obvious. Therefore, the strain sensor has wide application prospect in the aspect of wearable strain sensors.

Drawings

FIG. 1 shows the polymer Hy α CD-ACA-PEG₂₀₀₀₀Synthetic scheme for ACA.

FIG. 2 shows the lyophilized polymer Hy α CD-ACA-PEG₂₀₀₀₀Scanning electron microscopy images of ACA hydrogels.

FIG. 3 is the lyophilized polymer Hy α CD-ACA-PEG₂₀₀₀₀-ACA/CaCl₂Scanning electron microscopy images of hydrogels.

FIG. 4 shows the polymer Hy α CD-ACA-PEG₂₀₀₀₀ACAG' (storage modulus) and G "(loss modulus) as a function of strain.

FIG. 5 is the polymer Hy α CD-ACA-PEG₂₀₀₀₀ACAG' (storage modulus) and G "(loss modulus) as a function of frequency.

Fig. 6 is a diagram of a polymer access circuit.

FIG. 7 shows a sliding material Hy α CD-ACA-PEG₂₀₀₀₀ACA structural schematic.

Fig. 8 shows a stress-strain curve (a) and a tensile hysteresis curve (B) of the sliding material.

Detailed Description

The synthesis, preparation and application of the sliding material according to the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to the following examples. Specific details are set forth in order to provide a thorough understanding of the present invention in the preferred embodiments thereof. The starting materials used in the present invention are commercially available or commercially ordered and are described herein.

Example 1:

polymer monomer ACA-PEG₂₀₀₀₀-a process for the preparation of ACA comprising the following steps:

first, 10g (5 x 10) of the mixture was mixed^-4mol) dried polyethylene glycol (PEG, 20000) dissolved in 100mL dry CH₂Cl₂In (1). Then 50mL pyridine was added to the mixture and 240mg (1.26 x 10) was added dropwise^-3mol) p-toluenesulfonyl chloride (TsCl) and stirred at room temperature overnight. The mixture was washed 3 times with HCl (3moL/mL) and added to the organic phaseExcess solid sodium bicarbonate was added and stirred until no air bubbles were found. Then, the mixture was filtered, and the filtrate was dried and recrystallized from THF. The solvent was then removed, the product was dissolved in 150mL of ammonia water and stirred for 48 h. The product used 100mL CH₂Cl₂Extracted twice, then MgSO₄Dried and filtered. Then, the product is dissolved in anhydrous dichloromethane, added with triethylamine and acryloyl chloride, and cooled to room temperature N₂Reacting for 48h under the protection of gas. Finally, separating and purifying to obtain ACA-PEG₂₀₀₀₀-ACA。

Example 2

Polymer Hy alpha CD-ACA-PEG₂₀₀₀₀-a process for the preparation of ACA comprising the following steps:

200mg of ACA-PEG prepared in example 1 was added₂₀₀₀₀Dissolving ACA in 10mL of deionized water, and adding corresponding proportion of (ACA-PEG)₂₀₀₀₀-ACA: hy α CD is 1:0,1:5 or 1; 10) hy α CD (available from MW of chemical ltd, kyowawaruike, beijing: 1180) after 30 minutes of ultrasonic treatment, standing for more than 5 days at room temperature to obtain Hy alpha CD-ACA-PEG₂₀₀₀₀ACA pseudorotaxane crosslinker near clear suspensions.

Shaking 1mL of Hy alpha CD-ACA-PEG₂₀₀₀₀Mixing the nearly transparent suspension of ACA pseudorotaxane crosslinking agent with 3mL of acrylamide aqueous solution with the concentration of 300mg/mL, and adding 5mg I₂₉₅₉A photoinitiator. After simple shaking to make the system clear, the mixture was transferred to a teflon template and covered with a glass slide. Then, the gel was irradiated with 365nm ultraviolet light for 15min to obtain a polyrotaxane hydrogel (the light source was a portable ultraviolet lamp). Then, the mixture is immersed into aqueous solution of sodium hydroxide of 1,4 butanediol glycidyl ether (mass fraction is 20 percent) to form Hy alpha CD-ACA-PEG₂₀₀₀₀ACA slip ring hydrogel polymers. The calcium chloride-doped hydrogel is prepared by dissolving 0.2M CaCl in the solution before reaction₂And the other operations are unchanged.

Example 3

In the process of preparing the sliding material, the size of the tensile test sample strip shape is determined, and the method comprises the following steps:

the polymer was characterized by stretching using an AG-10T universal tensile machine. The sample strip for the tensile test is dumbbell-shaped, the length is 40mm, the width is 4mm, the thickness is 2mm, and the tensile speed is 100 mm/min. Such a shape facilitates the successful implementation of tensile tests. Other shaped samples are susceptible to shape distortion when stretched, which can affect experimental results.

Example 4

Acrylamide concentration, ACA-PEG₂₀₀₀₀-determination of ACA molecular weight comprising the following steps:

the acrylamide concentration is too low, the cross-linking density of the polymer is small, the tensile strength is low, the acrylamide concentration is too high, the gel brittleness is large, the flexibility is reduced, so that the acrylamide concentration of 300mg/mL is moderate through experiments, and in addition, the ACA-PEG₂₀₀₀₀The ACA molecular weight is suitably large to contribute to the elongation. In this experiment, the molecular weight of ACA-PEG-ACA was 20000 (ACA-PEG)₂₀₀₀₀-ACA)。

Example 5

HyαCD-ACA-PEG₂₀₀₀₀ACA-PEG in the preparation of-ACA pseudorotaxane crosslinker₂₀₀₀₀-ACA: the determination of the proportional size of Hy alpha CD comprises the following steps:

ACA-PEG is selected here₂₀₀₀₀-ACA: hy α CD is a ratio of 1:0,1:5,1:10, too small a Hy α CD ratio, longer tensile length, but poor recovery, too large a Hy α CD ratio, large Young's modulus of the polymer, good recovery, but too large strain loss. Therefore, ACA-PEG in the experiment₂₀₀₀₀-ACA: when Hy alpha CD is 1:5, the proportion is moderate, and the mechanical property of the polymer is excellent. See figure 8 for a detailed data diagram.

Example 6

The determination of the photoinitiator during the preparation of the sliding material comprises the following steps:

the common photoinitiator is Ammonium Persulfate (APS), but experiments show that when ammonium persulfate is used as the photoinitiator, the mixed solution of the pseudo-rotaxane cross-linking agent and the acrylamide is sensitive to light and easily forms a gel state, so that the mixed solution of the pseudo-rotaxane cross-linking agent and the acrylamide is not stable. But with I₂₉₅₉When used as a photoinitiator, the whole mixed liquid system is relatively stable and is irradiated by 365nm ultraviolet lightThe mixed solution of the pseudorotaxane crosslinking agent and the acrylamide generally does not form a gel. Therefore, we choose I here₂₉₅₉This is critical as a photoinitiator.

The specific description is as follows: the light source is a portable ultraviolet lamp, and the liquid before reaction and the photoinitiator are shaken up as much as possible.

The specific description is as follows: the hydrogel polymer is shown by an electron microscope, the interior of the hydrogel polymer is of a three-dimensional network structure, and the surface of the hydrogel polymer is flat and smooth as a whole.

The specific description is as follows: the electron microscope shows that after the metal salt ions are added, the hydrogel polymer still has a three-dimensional network structure inside, but the whole body appears to have a plurality of protrusions, which are the result of combination of ionic bonds and covalent bonds. So that the gel tensile mechanical property is more excellent.

The specific description is as follows: it can be seen that as the strain increases, G' (storage modulus) is consistently greater than G "(loss modulus) over a wide range of 0.1% to 3000%.

The specific description is as follows: in the sweep frequency curve, the relatively large G' and the relatively small G "gradually increase and remain substantially parallel as the frequency increases from 0.1% to 100%. These results are sufficient to demonstrate the high stability of the three-dimensional network of the hydrogel.

Figure 6 is a hydrogel access circuit diagram.

The specific description is as follows: the hydrogel may be conductive to brighten the bulb and when the hydrogel is stretched the bulb may darken. The change value of the resistance is obvious after the gel is stretched. Therefore, the strain sensor has wide application prospect in the aspect of wearable strain sensors.

Fig. 7 is a schematic structural view of a sliding material.

The specific description is as follows: since the sliding material is a polymer, the structure of the polymer cannot be given, only a schematic structural diagram can be given, and parts of the schematic structural diagram are clearly indicated together.

FIG. 8 is a stress-strain curve and a tensile hysteresis curve of a sliding material.

The specific description is as follows: ACA-PEG is selected here₂₀₀₀₀-ACA: hy α CD is 1:0,1:5,1:10, and the ratio of monomer Hy α CD is too small, and the tensile length is longer, but the recovery performance is poor, while the ratio of Hy α CD is too large, and the Young's modulus of the polymer is large, and the recovery performance is good, but the strain loss is too large. Therefore, ACA-PEG in the experiment₂₀₀₀₀-ACA: when Hy alpha CD is 1:5, the proportion is moderate, and the mechanical properties of the polymer are excellent (to say, the monomer proportion we only select ACA-PEG here₂₀₀₀₀-ACA: Hy α CD ═ 1:0,1:5,1:10 in several ratios. However, it can be seen from FIG. 8 that the Hy α CD ratio is too small and the tensile length is longer, but the recovery performance is poor, while the Hy α CD ratio is too large and the Young's modulus of the polymer becomes large and the recovery performance becomes good, but the strain loss is too large. In fact, because Hy α CD has better solubility in water, more Hy α CD can be added in water. In addition, ACA-PEG is known in the literature to ensure good tensile properties₂₀₀₀₀Too much rotaxane crosslinker formed by ACA and Hy α CD cannot be added. In general, the crosslinking agent content is preferably 1% or less in the whole system. ).

Claims

1. Hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide Hy alpha CD-ACA-PEG based₂₀₀₀₀-sliding material of ACA, characterized by being constituted by a monomer having the following structure:

the sliding material is prepared by firstly allowing ACA-PEG to be in aqueous solution₂₀₀₀₀Forming pseudorotaxane by using-ACA and Hy alpha CD, mixing the pseudorotaxane serving as a cross-linking agent with an acrylamide solution, adding a photoinitiator, forming a three-dimensional network structure under the photoinitiation condition, and adding sodium hydroxide strong base to enable ACA-PEG to form₂₀₀₀₀-Hy α CD in ACA molecular chain is reacted with 1,4 butanediol glycidyl ether to bridge Hy α CD with 1,4 butanediol glycidyl ether to form the said sliding material.

2. Hydroxypropyl α -cyclodextrin and acrylamide polyethylene glycol acrylamide Hy α CD-ACA-PEG based on claim 1₂₀₀₀₀-a process for the preparation of a sliding material of ACA, characterized in that it comprises:

(1) monomeric ACA-PEG₂₀₀₀₀Synthesis of-ACA

First, 1-10g of dried polyethylene glycol PEG20000 is dissolved in 30-120mL of dried CH₂Cl₂Then adding 12-60mL pyridine into the mixture, dropwise adding 80-240mg p-toluenesulfonyl chloride, and stirring at room temperature overnight; the mixture was washed with 2.8-3.2moL/mL HCl and excess solid sodium bicarbonate was added to the organic phase and stirred until no air bubbles were found;

then, filtering, drying the filtrate, recrystallizing with THF, then removing the solvent, dissolving the product in 145-160mL ammonia water, and stirring for 48-60 h; the product is used with 80-120mL CH₂Cl₂Extracted and then passed through 10-50g MgSO₄Drying and filtering; then, the product is dissolved in 80 to 120mL of anhydrous dichloromethane, triethylamine in 5 to 10 times of the molar equivalent of the product and acryloyl chloride in 5 to 10 times of the molar equivalent of the product are added, and the mixture is subjected to N reaction at room temperature₂Reacting for more than 48h under the protection of gas, and finally separating and purifying to obtain ACA-PEG₂₀₀₀₀-ACA；

(2) Polymer Hy alpha CD-ACA-PEG₂₀₀₀₀Synthesis of-ACA sliding Material

195-205mg of ACA-PEG₂₀₀₀₀Dissolving ACA in 9.5-10.5mL deionized water, and adding the solution according to ACA-PEG₂₀₀₀₀Adding Hy alpha CD into ACA and Hy alpha CD in the ratio of 1:5 or 1:10, ultrasonic treating, and standing at room temperature to obtain Hy alpha CD-ACA-PEG₂₀₀₀₀-an ACA pseudorotaxane cross-linker near-transparent suspension;

3. Hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide Hy alpha CD-ACA-PEG based on claim 2₂₀₀₀₀A process for producing a sliding material of ACA, characterized in that CaCl is dissolved in a reaction precursor solution before photoinitiation₂And other operations are unchanged, so that the calcium chloride-doped sliding material is obtained.

4. Hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide Hy alpha CD-ACA-PEG based on claim 2₂₀₀₀₀-process for the preparation of a sliding material of ACA, characterized in that: prepared monomer ACA-PEG₂₀₀₀₀ACA contains amide bonds, is more stable than ester bonds, and is not easily hydrolyzed in the presence of strong bases.

5. Hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide Hy alpha CD-ACA-PEG based on claim 2₂₀₀₀₀-process for the preparation of a sliding material of ACA, characterized in that: said ACA-PEG₂₀₀₀₀The ratio of-ACA to Hy α CD is ACA-PEG₂₀₀₀₀-ACA: when Hy alpha CD is 1:5, the proportion is moderate, and the mechanical property of the polymer is excellent.

6. Hydroxypropyl alpha-cyclodextrin and acrylamide polyethylene glycol acrylamide Hy alpha CD-ACA-PEG prepared by the method of any one of claims 2 to 5₂₀₀₀₀The sliding material of ACA is applied to the manufacture of wearable strain sensors for monitoring human body movement.