Self-assembly in aqueous solutions of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(vinyl alcohol)

A novel class of self-assembling amphiphilic polymers is introduced whereby a Pluronic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer is end-modified by poly(vinyl alcohol) (PVA). The copolymer is temperature-sensitive in aqueous solutions due to the temperature-dependent water solubility of PPO. The Pluronic-PVA copolymers show a dramatic temperature dependency of their aggregation. The attachment of PVA segments to the Pluronic molecule increases its critical aggregation temperature. At concentrations of 10% and higher and temperatures above 10-20 degrees C, the Pluronic-PVA aqueous solutions yield gels. The gelation and formation of large aggregates coincide, indicating that the gelation is caused by the formation of aggregates with interpenetrating coronas. A decline in the power law relaxation exponent of the light scattering is observed upon gelation, which is due to the nonergodicity of the gels.