Novel Family of Thermogelling Materials via C−C Bonding between Poly(acrylic acid) and Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)

Abstract

Pluronic poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymers are copolymerized with poly(acrylic acid) (PAA) by a one-step free-radical polymerization of acrylic acid with the chain transfer to the Pluronic dissolved in the acrylic acid. Exponential increase of branching and cross-linking in the resulting Pluronic−PAA copolymers is observed at high degrees of conversion of acrylic acid. The solutions show reversible gelation within a narrow temperature range, with a gelled state resembling that of permanently cross-linked gels. Onset of thermogelation in Pluronic−PAA solution coincides with augmentation of light-scattering intensity of large scatterers and approaches the critical micellization temperature of the parent Pluronic. Effects of the overall PEO content and the length of the PPO segment in the parent Pluronic on the properties of copolymers are revealed.