Tailoring of stimuli-responsive water soluble acrylamide and methacrylamide polymers

The tailoring of the lower critical solution temperature (LCST) polymers of acrylamide and methacrylamide in water is achieved by chemical modification of freely water soluble precursor polymers poly[N-2-hydroxypropylmethacrylamide], poly[N,N-bis(hydroxyethyl)acrylamide] and poly[N-(tris(hydroxymethyl)-methyl)acrylamide]. Two principal reactions, namely acetylation and cinnamoylation, are applied. By varying the acylating agent as well as the extend of acylation, the LCST can be tailored easily. The cloud points observed for the different polymer series do not correlate with the apparent hydrophilicity of the parent polymers according to the content of hydroxyl groups. The results thus exemplify the difficulties to predict the behavior of modified thermosensitive polymers by simply analysing the balance of hydrophilic to hydrophobic molecular fragments. Chemical modification by cinnamoylation provides photoreactive copolymers e.g susceptible to photocrosslinking. When the polymers are prepared by polymerization using a disulfide-functionalized azo-initiator efficient grafting of the modified copolymers on gold surfaces is possible to prepare ultrathin hydrogel films, as demonstrated by Surface Plasmon Resonance.