TRANSIENT NETWORKS IN ABA BLOCK COPOLYMER-MICROEMULSION SYSTEMS

ABA block copolymers (with hydrophilic A-blocks (POE) and a hydrophobic B-block (PI) have been shown to induce gel formation in water-in-oil microemulsions.1 Gelation is preceded by a pronounced change of the viscosity at low copolymer concentration. This change resembles the dilute-to-semidilute transition encountered in solutions of polymer chains in good solvents. It is attributed to the formation of a transient network interconnecting microemulsion droplets via the apolar B-blocks. The relaxation time of disentanglement of A-blocks and the droplets is about 10 ms at 298 K, i.e., on the order of the lifetime of the micellar aggregates. © 1990, American Chemical Society. All rights reserved.