Volume phase transition of N-isopropylacrylamide gels crosslinked by a crosslinker with six hands.

Crosslinkers play an essential role in determining the physical properties of gels. We synthesized a new type of crosslinker with three vinyl groups [trisacrylaminomethan (TRI), which joins six polymer chains per single molecule]. We found that N-isopropylacrylamide (NIPA) gels crosslinked with the new crosslinker gel at a much lower fraction of crosslinker than the gel crosslinked with popular N,N'-methylenebisacrylamide (BIS). We also found that the NIPA gels with TRI crosslinker displayed larger discrete volume changes at the volume phase transition. We discuss the effects of the average length of NIPA chains between two crosslinkers on the volume phase transition as well as the effects of inhomogeneity in gels caused by a low fraction of crosslinker.