ORDERING AND STRUCTURE FORMATION IN TRIBLOCK COPOLYMER SOLUTIONS .1. RHEOLOGICAL OBSERVATIONS

The linear viscoelastic properties of a poly(styrene)-poly(ethylene, b utylene) triblock copolymer in the presence of a hydrocarbon oil have been investigated. The samples were followed rheologically, during ann ealing at different temperatures. In a relatively small temperature in terval, tan delta-curves, recorded at different frequencies, evolved i n a pattern which is typical for a physical gelation. It allowed deter mination of the gel time. The kinetics of gel formation were found to be affected by the annealing temperature, and the rate was maximum at an intermediate temperature that depended on the polymer content of th e sample. Increasing the polymer content shifted this maximum to highe r temperatures. At lower temperatures, a glass transition of the polys tyrene end-blocks was detected. The microphase separation temperature however, could not be determined. In addition, the influence of strain and the applicability of time-temperature superposition was analysed. (C) 1997 Elsevier Science Ltd.