Effect of silk sericin content on the mophology and thermal stability of temperature-sensitive hydrogels

The poly(N-isopropylacrylamide)(polyNIPAM) hydrogels with various silk sericin (SS) content were successfully prepared by semi-interpenetrating network (semi-IPN) method. The structure, compatibility and thermal stability of hydrogel, including the internal pore shape and volume phase transition behavior of hydrogels, were investigated by XRD, SEM, DSC and TGA-DTG. The results show that hydrogen bond acting force can be found between silk sericin polypeptide chains and polyNIPAM molecular chains. With increasing mass faction of silk sericin from 0 to 20%, the interior pore size of PNIPAM hydrogel increases by one or two times and presents honeycomb patterned structure. The SS chains homodisperse into the hydrogel matrix without any phase separation. In comparison with volume phase transition temperature(VPTT) value of pure polyNIPAM hydrogel, the introduction of silk sericin molecular chains leads to temperature enhancement of 0.2-0.3℃. The maximum thermal decomposition temperature and DTG decomposition temperature increase gradually.