Ordering and structure formation in triblock copolymer solutions .2. Small angle X-ray scattering and calorimetric observations

The morphology and thermal properties of a poly(styrene)-poly(ethylene, butylene) triblock copolymer in the presence of a selective solvent has been investigated, using small-angle X-ray scattering (SAXS) and calorimetry (d.s.c.). The temperature dependence of the SAXS profiles indicated a transition, which was associated with a thermal destruction of the superlattice, preserving the nearest neighbour distance between the micro domains. The transition temperature was referred to as the disordering temperature (T-d). On heating, the loss of long range order was observed as a sudden broadening of the line profiles of the first order peak. At higher temperatures a gradual disappearance of this first order peak was interpreted as a gradual dissolution of the micro domain structure. Simultaneously, calorimetric investigations revealed two transitions on heating: at lower temperatures a glass transition, followed by an endothermic transition. The onset of the endotherm corresponded to T-d. In addition, the onset of how, which has been reported in Part I of this series, also corresponded to T-d Annealing at intermediate temperatures resulted in the formation of large scale ordering. This ordering could be followed by X-ray scattering and corresponded to changes observed in the rheological behaviour. (C) 1997 Elsevier Science Ltd.