DETERMINATION OF SHARPNESS OF ORDER-DISORDER TRANSITION OF BLOCK-COPOLYMERS BY SCATTERING METHODS

It has been considered that elastic scattering profiles gradually change with temperature across the order-disorder transition (ODT) of block copolymers and hence a unique determination of the ODT temperature (T(ODT)) is difficult by scattering methods alone. We report here our finding that the scattering experiments with a high temperature-resolution, involving a temperature increment of smaller than or equal to 1-degrees-C, enables a straightforward, unequivocal determination of T(ODT) even for a low molecular weight polystyrene-block-polyisoprene copolymer. Moreover we found that the high temperature-resolution scattering experiment can reveal the very sharp ODT of the copolymer occurring in a very narrow temperature range of less than 1-degrees-C; the experimental results with a low temperature-resolution can easily lead us to overlook the sharpness of the ODT and to misunderstand the nature of the transition.