A strategy to introduce the pH sensitivity to temperature sensitive PNIPAAm hydrogels without weakening the thermosensitivity

A series of novel pH and thermosensitive hydrogels, comprised of N-isopropylacrylamide (NIPAAm) and N-isopropyl-maleamic acid (NIPMMA) units were designed and fabricated. The resultant P(NIPAAm-co-NIPMMA) hydrogels were characterized and it was found, with the increasing content of NIPMMA, that the pH sensitivity of P(NIPAAm-co-NIPMMA) hydrogel improved, whilst the temperature sensitivity remained almost the same. This unique intelligent character was attributed to the existence of a continuous isopropylamide sequence in P(NIPAAm-co-NIPMMA) hydrogels.