Rheological properties of aqueous micellar gels of a thermo- and pH-sensitive ABA triblock copolymer.

This article presents a systematic study of the effect of pH on the rheological properties of aqueous micellar gels formed from 10.0 wt % aqueous solutions of a thermo- and pH-sensitive ABA triblock copolymer, poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid)-b-poly(ethylene oxide)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid) (P(DEGEA-co-AA)-b-PEO-b-P(DEGEA-co-AA)). The block copolymer was synthesized by atom transfer radical polymerization of DEGEA and tert-butyl acrylate with a molar ratio of 100:5 from a difunctional PEO macroinitiator and subsequent removal of tert-butyl groups using trifluoroacetic acid. PDEGEA is a thermosensitive water-soluble polymer with a cloud point of 9 °C in water. The thermo-induced sol−gel transition temperature (Tsol−gel) of the 10.0 wt % aqueous solution of P(DEGEA-co-AA)-b-PEO-b-P(DEGEA-co-AA) can be continuously and reversibly tuned over a wide temperature range by varying the solution pH. The sol−gel transition became broader with the increase of p...