Sol-Gel-Sol-Cloudy Transitions of Aqueous Solutions of Multi-Responsive Hydrophilic Diblock Copolymer Poly(methoxytri (ethylene glycol) acrylate-co-acrylic acid)-b-poly(ethoxydi(ethylene glycol) acrylate)

摘要

Stimuli-responsive block copolymer aqueous micellar gels have received considerable attention due to their potential applications in a wide variety of fields, particularly in biomedical areas such as sustained and triggered release of substances and tissue engineering.1-4 Usually, the sol-gel phase diagram of a thermosensitive hydrophilic diblock copolymer in water at low/moderate concentrations is a C-shaped curve.1,3 For a diblock copolymer with a particular molecular weight and a specific composition, its sol-gel phase diagram is fixed. Although the addition of salts can modify the phase diagram, the changes are irreversible.3 Herein, we present a strategy to tune the upper boundary of the sol-gel phase diagram of a thermosensitive hydrophilic diblock copolymer. The polymer, poly(methoxytri(ethylene glycol) acrylate-co-acrylic acid)-b-poly(ethoxydi(ethylene glycol) acrylate) (P(TEGMA-co-AA)-b-PDEGEA), was prepared by reversible addition-fragmentation chain transfer polymerization (RAFT) (Scheme 1). The higher LCST block of the diblock copolymer contained a small amount of carboxylic acid groups, and thus its LCST can be tuned by changing the pH of the solution, which allowed us to shift the upper boundary of the sol-gel phase diagram.