Tunable Upper Critical Solution Temperatures for Acrylamide Copolymers with Bile Acid Pendants

Acrylamide derivatives of bile acids are chosen as a hydrophobic comonomer to copolymerize with acrylamide via reversible addition and fragmentation chain transfer (RAFT) polymerization to afford a series of copolymers of P(AAm-co-CAA). These copolymers exhibit a sharp and reversible insoluble-soluble transition in water upon heating to a mixing temperature (T_mix) related to the upper critical solution temperature (UCST). T_mix of these copolymers can be conveniently tuned to a practical temperature range, around 37 °C for biomedical applications. T_mix rises with increasing molar fraction of the bile acid-based acrylamide and increasing concentration of the aqueous solution of the copolymers. The addition of a natural host molecule β-cyclodextrin lowered the T_mix. The insoluble-soluble transition of the copolymers was also evidenced by dynamic light scattering and transmission electron microscopy. The biocompatible nature of the bile acids and β-cyclodextrins may make these copolymers potentially useful for biomedical applications.