Synthesis of hydrogels by radiation-induced cross-linking of Pluronic® F127 in N2O-saturated aqueous solution

Abstract

Pluronic F127, a tri-block copolymer of poly(ethylene oxide) and poly(propylene oxide) of a nominal formula EO100-PO65-EO100, when subjected to the action of ionizing radiation in oxygen-free, N2O-saturated aqueous solution, undergoes predominantly cross-linking by intermolecular recombination of polymer-derived radicals. This manifests itself as an increase in average molecular weight and, at sufficiently high doses, as a formation of permanent hydrogel. Cross-linking occurs with high yields. Side reactions include chain scission and traces of oxidation processes. Polymer concentration and temperature influence the yields of radiation-induced reactions. This indicates that radiolysis mechanism depends on the spatial arrangement of Pluronic molecules, which can be organized into single chains, micelles, and physical gel. Macroscopic hydrogels of Pluronic are thermo-sensitive (phase transition temperature behavior with the transition temperature, at the tested conditions, of ca. 27 °C). Pluronic gels are prone to oxidative degradation, both in an aqueous environment and in the dry state, especially at elevated temperatures. Copyright © 2006 John Wiley & Sons, Ltd.