Temperature sensitivity of a hydrogel network containing different LCST oligomers grafted to the hydrogel backbone

Abstract

Hydrogels (HGs) containing two different lower critical solution temperature (LCST) oligomers grafted to the same HG backbone were synthesized using macromonomers of the LCST oligomers. Carboxy-terminated oligo(N-iso-propylacrylamide) (oNIPAAm) oligo(N-vinylcaprolactam) (oVCL) and a random co-oligomer of NIPAAm and acrylamide (AAm) (o[NIPAAm-co-AAm]) were selected as the LCST oligomers. The macromonomers were synthesized by reaction of the terminal carboxy groups with glycidyl metha-crylate. Using AAm as the base monomer for the HG macromonomers of the carboxy-terminated oNIPAAm and oVCL were copolymerized with AAm and a cross–linker and the HG was obtained. Despite the lack of temperature-sensitivity of the PAAm HG the grafted HG showed two volume phase transitions corresponding to the LCSTs of the grafted side chains of oNIPAAm and oVCL.