Synthesis of Thermo-responsive Poly(N-isopropylacrylamide) Hydrogels by rontal Polymerization

摘要

The synthesis of thermo-responsive hydrogels poly (Nisopropylacrylamide) (PNIPA) via frontal polymerization (FP) was carried out in four mixed solvents, i.e. dimethylsulfoxide (DMSO) mixing with water, ethanol, tetrahydrofuran (THF) and acetone, respectively. The obtained samples were characterized and compared in term of their yield, thermo-response behavior and microstructure. It was found that the application of mixed solvent didn't compromise the thermo-responsive feature of PNIPA hydrogels. All the samples underwent a drastic swelling transition at about 32 ℃ in aqueous solution. Furthermore, the category and content of the solvent of lower boiling point caused remarkable difference in features of PNIPA hydrogels. The sample prepared in DMSO/water mixed solvent was characterized by die highest yield and the lowest font temperature (Tmax) and velocity (Vf), whereas one synthesized in DMSO/THF mixture exhibited the smallest yield and the highest front temperature. Solvent composition influenced the porous morphologies of the samples remarkably and, consequently their water swelling capability. The novel honeycomb cells were observed in PNIPA hydrogel synthesized in DMSO/THF, their big size being responsible for the higher swelling ratio as compared to ones synthesize in the others mixed medium. The sample obtained in DMSO/water solvent showed the lowest swelling ratio due to the highest crosslink degree among these prepared in DMSO/water, DMSO/ethanol and DMSO/acetone mixture. Also, increasing the relative amount of lower-boiling-point solvent in mixed solvent led to a decrease in frontal temperature and an improvement in swelling capability of the hydrogel.