Effect of polymer complex formation on the cloud-point of poly(N-isopropyl acrylamide) (PNIPAAm) in the poly(NIPAAm- co-acrylic acid): polyelectrolyte complex between poly(acrylic acid) and poly(allylamine)

Abstract

A series of pH/temperature-sensitive polymers which contain both temperature and pH-sensitive components were synthesized by copolymerizing N-isopropyl acrylamide (NIPAAm) and acrylic acid (AAc). The influence of poly(allylamine) (PAA) as the polyelectrolyte on the lower critical solution temperature (LCST) of pH/temperature-sensitive polymers was investigated in the pH range of 2–12. The LCSTs of PNIPAAm/water in P(NIPAAm- co-AAc) were determined by cloud-point measurements. The LCSTs of PNIPAAm/water in the copolymers were strongly affected by the pH, the presence of polyelectrolyte solute and AAc content in the P(NIPAAm- co-AAc). The polyelectrolyte complex between P(NIPAAm- co-AAc) and PAA was formed from the p K a of PAAc to the p K b of PAA. Also, the LCSTs of the PNIPAAm in the copolymers were dependent on the charge density of the PAAc and concentration of the PAA.