Preparation And Properties Of Gelatin Composite Hydrogels

Gelatin is a hydrolyzed product of natural polymer collagen.It contains a large number of reactive functional groups such as amino,carboxyl and hydroxyl groups.It has low antigenicity,good biocompatibility,biodegradability and temperature-sensitive reversible gelation properties etc.In recent years,hydrogels prepared on gelatin-based materials have become one of the most popular gel studies.In this paper,gelatin-based materials were used to form composite hydrogels under different reaction conditions,such as pH-responsive micelles（PMMS）,methylol acrylamide（HAM）and methacrylic acid（MAA）.The properties of each of the above composite hydrogels were investigated.The main contents and results of the thesis are as follows:（1）Preparation and properties of Gelatin/PMMS composite hydrogels.Firstly,PMMS latex particles with good pH response with particle size of about 300 nm were prepared by Pickering emulsion polymerization.Then,PMMS latex particles and gelatin were combined to form Gelatin/PMMS composite hydrogel under pH induction;Optimize gel properties.SEM observation showed that the microstructure of the composite hydrogel under pH induction has a more closely related semi-collapse structure and morphology.The dynamic rheometer tests the rheological properties of the gel.As the gel modulus increases to 15%with gelatin content,the storage modulus of the composite gel also increases.However,the critical strain valueγ*decreases as the gelatin content increases.With the increase of latex particle content,the storage modulus of the composite gel also increases.When the latex particle content is 15%,the storage modulus is up to 10,000 Pa.The step rheological scan results show that the gel has the self-healing ability of the reconstructed gel network.The universal testing machine test showed that when the composite gel composition was G₁₀P₁₃,it had the best tensile and compressive properties,tensile strength of 108 kPa,and elongation at break of 350%.The compressive strength is 0.59 MPa and the compression modulus is 3.59MPa.The macroscopic self-healing properties of the composite hydrogel were characterized by rhodamine red staining.In general,Gelatin/PMMS composite hydrogels have good mechanical properties and self-healing ability.（2）Preparation and properties of Gelatin/PHAM composite hydrogel.A mixed system of gelatin and methylol acrylamide forms a double-networked Gelatin/PHAM composite hydrogel by free radical polymerization;the composition ratio is changed to optimize the gel properties.The network structure of the gel was observed by SEM,and the network structure was a dense and uniform porous network structure.The dynamic rheometer test analyzed the influence of gel composition on the rheological properties of the system.The gel modulus and critical strain increased with the change of HAM ratio,and the contribution of HAM component to the storage modulus of composite gel was better.Big.The mechanical properties of the composite gel were tested by universal testing machine.The energy dissipation process and resilience performance of the composite gel were studied.The result is that the fracture energy of G₁₅PHAM₁₀ composite gel is 194.39 kJ/m³,tensile strength is99.3 kPa,and elongation at break is obtained.The long rate is 316%.The energy dissipation mode of the Gelatin/PHAM composite gel during the stretching process is a dual network mode and has good compression resilience.The biocompatibility of the composite gel was investigated by BSA adsorption test and anti-hemolytic test.The results showed that the composite gel had less BSA adsorption and hemolysis rate.It was stained with rhodamine and the gelatin/PHAM composite hydrogel had good macroscopic self-healing ability at60°C.The dual-network Gelatin/PHAM composite hydrogel with gelatin as the physical cross-linking network and PHAM self-crosslinking to form a chemical cross-linking network enhances the mechanical properties and self-healing ability of gelatin-based hydrogels without reducing the biocompatibility.（3）Preparation and properties of Gelatin/PMAA composite hydrogel.The gelatin aqueous solution and the methacrylic acid without the cross-linking agent were directly mixed,and the Gelatin/PMAA composite hydrogel was formed by radical polymerization;the composition ratio was changed to optimize the gel properties.The rheological properties of the gel were tested by dynamic rheometer.With the increase of PMAA content in the gel composition,the modulus of the gel increased first and then decreased with the increase of the content of MAA.The universal testing machine test showed that the maximum elongation at break of the Gelatin/PMAA composite hydrogel was 340%and the maximum compressive modulus was 2.37 MPa.The swelling properties of Gelatin/PMAA composite hydrogel in deionized water and PBS buffer solution were tested.The results show that the time to reach the swelling equilibrium of Gelatin/PMAA composite hydrogel increases with the increase of MAA content,and the swelling balance rate is then reduced.The conductivity and strain sensing ability of Gelatin/PMAA composite hydrogels were studied.The highest conductivity was as high as 6.52×10^-33 S cm^-1,and the conductivity was different under different deformations,which has potential application of strain sensors.