Preparation And Characterization Of Micelles Crosslinked Tough Gel

Polymer hydrogels are three-dimensional polymer networks with high water content.It's special bionics,biocompatibility,flexibility of molecular chains and three-dimensional network structure,as well as its responsiveness to external stimuli such as pH,ionic strength,light,temperature,etc.have attracted a large number of scholars to study on it.Potential applications include tissue engineering,adhesives,drug delivery,sensors,artificial muscles,soft robots,energy storage and conversion,and electrochemical equipment.However,traditional hydrogels usually show poor mechanical strength or toughness due to the inhomogeneity of cross-linking and reticular structure and the lack of sufficient energy dissipation mechanism to prevent the rapid propagation of microcracks and stress concentration.Under the action of load,the redistribution of stress in the non-uniform network results in the rapid concentration of stress on the structural defects of the network.As a result,the cracks spread rapidly through the network and the gel was created.The practical application of hydrogels is severely limited.In order to improve the application range of hydrogels,a series of strong and tough hydrogels were prepared,including double network hydrogel,sliding chain hydrogels,nanocomplex hydrogels,etc.However,most hydrogels become hard and brittle after dehydration due to the properties of hydrophilic polymer chains,which greatly reduces their application fields.In addition,in the field of drug delivery,hydrogels with high mechanical strength and high loading rate for some special hydrophilic drugs,such as growth factor,are still rarely reported.Based on the above ideas,this paper has carried out the following work1.Preparation and characterization of a hydrogel-elastomer integration material crosslinked by Pluronic micelles.Inspired by the functions of leeches,for the first time homogeneous materials integrating hydrogels and elastomers were achieved by free radical polymerization.2-Methoxyethylacrylate(MEA)was used as elastomer monomer and Pluronics functionalized with vinyl groups acted as cross-linkers to impart the hydrogel property to the materials.The swelling property,water retention property,mechanical property and self-healing property of the gel were measured.The resulting Pluronic/PMEA gels possess a swelling ratio of about 210% and good water-retaining ability.Compression tests of Pluronic/PMEA gels at swelling equilibrium state show a stress up to 1.6 MPa under 85%strain.The gels act as elastomer after dehydration.Uniaxial tensile fracture stress and the elongation reached 1200 kPa and 500%,respectively,and compression stress was above 22 MPa.Furthermore,the Pluronic/PMEA gels also show self-healing properties.All the Pluronic/PMEA gel has the self-healing efficiency of 40% in 5 ?.2.Preparation and characterization of a host and guest micellar cross-linked hydrogel and the micellar encapsulation of growth factors.Single methyl ended polyethylene glycol(mPEG)with was modified with trithiocarbonate as the chain transfer agent,and a hydrophilic two-block polymer chain was obtained by reversible addition-fragmentation chain transfer polymerization with N-isopropyl acrylamide(NIPAM).After the double bond was modified on one end of the PNIPAM,the PEG chain segment and the ?-cyclodextrin(?-CD)formed hydrophobic rigid chain segment through the host and guest interaction,and formed micelle by self-assembly through hydrophilic and hydrophobic action in water.This host-guest micelle was compared with the control group of Pluronic F127 micelles in the nerve growth factor(NGF)encapsulation test.The results showed that the host-guest micelle encapsulation rate was more than 2 times of F127 micelles.Furthermore,the host-guest micelles were used as cross-linkers to copolymerize with acrylamide monomer(AAm)to obtain a super-stretched host-guest micelle hydrogel.The morphology,water content,swelling ratio and mechanical properties of the hydrogel were characterized,and the results showed that the hydrogel had porous structure,with water content and swelling rate of 65% and 811%,respectively.The hydrogel showed a super elastic property,the elongation was more than 20 times of its original length,and the strength was more than 2 times higher than the control group,and the cyclic tensile test showed that the hydrogel had a good stress dissipation mechanism and resilience.Pluronic/PMEA gel is characterized by simple preparation,excellent mechanical properties in both dry and wet states and self-healing after damaged.Furthermore,the hostguest micelles prepared by us have achieved high efficiency in the encapsulation of nerve growth factor,and the micelles can also be used to enhance the mechanical properties of hydrogels.We expect that these two kinds of gels can be used in soft robots,artificial muscles,wound dressings and other fields.