Phase-separation structure of polymer blend of polystyrene and polyisoprene in the presence of styrene-isoprene diblock copolymer

The micro-phase-separation structure of a system of homopolymers and a block copolymer was investigated theoretically and experimentally. Phase-separation experiments were carried out for the blend system of homopolystyrene and homopolyisoprene in the presence of styrene-isoprene diblock copolymer, employing solvent casting as the method for the formation of phase separation. The experimental results revealed a lamellar structure in the micro-phase-separation, and domain spacings of the structure were measured. A model for the lamellar structure of copolymer/homopolymer systems is proposed to predict the domain spacing on the basis of the statistical thermodynamic theory of Whitmore and Noolandi. The model can predict the domain spacing well in most cases.