Preparation And Rheological Properties Of Nanogel Aqueous Dispersions/supramolecular Composite Hydrogel

Poly(N-isopropylacrylamide) nanogels are hydrogel nanoparticles , which average particle size is 1-1000nm. The nanogel dispersions have significant thixotropy and fast temperature response. Higher concentration of PNIPAM nanogel aqueous dispersions can occur the sol-gel phase transition near its lower critical solution temperature, which can be used as an injectable material for interventional therapy, drug delivery and tissue engineering. However, the critical gelation concentration of PNIPAM nanogel aqueous dispersions are very high (～10 wt/V%),which would induce high viscosity, high cost , inappropriate clinical use of gels. Low molecular weight hydrogelator only need very low concentration (0.1～2wt%) to occur gelation, but the strength of gels are weak.Based on the characters of two materials, we add PNIPAM nanogel dispersions into a kind of L-phenylalanine acid derivatives (TC₁₈PheBu), this measures may reduce concentration and viscosity of nanogels to gelation ,even enhence the liquidity of solution and the strength of gels.The main contents and results are as follows:(1)The synthesis, purification and characterization of hydrogelator TC₁₈PheBu. According to the method in literature, synthesizing hydrogelator TC₁₈PheBu. Using IR and 1H NMR to confirm its structure。(2)Testing the lowest gelation concentration and the phase transition temperature of composite hydrogels system. The results indicate that low concentration PNIPAAm nanogel dispersions can greatly reduce the lowest gelation concentration of hydrogelator TC₁₈PheBu,while high concentration nanogel dispersions can reduce more. DSC testing show that pure hydrogels formed by TC₁₈PheBu had only one phase transition temperature, but joined the PNIPAAm nanogel dispersions, the volume shrinkage of nanogel dispersions and the collapse of three-dimensional network structures of gels caused composite hydrogels have two phase transition temperature. (3)characterizing microstructure of the composite hydrogels system. Polarizing microscope , field emission scanning electron microscopy, atomic force microscopy photographs indicate that pure hydrogels have typical three-dimensional network structure,but the PNIPAAm nanogel dispersions will destroy three-dimensional network structure by adding, adding the concentration of nanogel dispersions are much higher, the destructive effects will be greater.(4)Study about rheological properties of composite hydrogels.Comparing the rheological properties of composite hydrogels of different concentration with pure hydrogels, the elastic modulus and loss modulus of composite hydrogels are greatly enhanced, indicating that adding the nanogel dispersions can enhance the strength, mechanical properties and deformation response capacity of gels, What is worth to mention, when the nanogels concentration up to a critical value,the elastic modulus and loss modulus of composite hydrogels will be lower ,but still higher than that of pure hydrogels.