Body temperature-responsive gels derived from hydroxypropylcellulose bearing lignin

Hydroxypropylcellulose bearing lignin (HPC-L) prepared from softwood by the atmospheric acetic acid pulping followed by derivatization showed the lower critical solution temperature (LCST) of approximate 38degreesC in 2% aqueous solution, which were 5degrees lower than that of pure HPC with a similar molecular mass to HPC-L. Two types, urethane and epoxy, of chemical gels were prepared from HPC-L and HPC using hexamethylene diisocyanate and polyethylene glycol diglycidyl ether as crosslinkers, respectively. The urethane-type gels from both HPC's have undergone shrinking at less than 20degreesC. This thermoresponse of the gels did not reflect LCST of the sources. Such low temperature shrinking was brought about by the hydrophobicity of crosslinker. On the other hand, the epoxy-type gels showed a very similar volume transition temperature (VTT) upon shrinking to LCST; the epoxy-type HPC-L gel showed VTT at 38degreesC, while the corresponding HPC gel had VTT at 46degreesC. This difference in VTT as well as LCST was attributable to hydrophobicity of lignin dangled to HPC. Thus, the body temperature-responsive gel can be prepared from HPC-L with the water-soluble crosslinker. (C) 2004 Elsevier Ltd. All rights reserved.