Abstract
Microdomain structures of binary mixtures of poly(butadiene-b-ethylene oxide) diblock polymer (PB-b-PEO) and homopolybutadiene (PB) were investigated as a function of volume fraction of PB in the mixtures by using small angle X-ray scattering (SAXS). The crystallization behaviors of these blends were also studied by differential scanning calorimetry (DSC) to combine the data with microstructures. When blending in 0.69 volume fraction of PB, the morphology were changed from lamellae to hexagonally packed cylinder and an enormous change on the freezing point when crystallizing were observed. As adding more PB into block copolymer, the morphology was transferred further to spherical microdomain and the freezing point were more depressed. It was assumed that the crystallization rate was related with the continuities of microdomains. Different microdomain needed its own nucleus to enlarge PEO spherulite. Such a nucleation process became the rate-determined step in crystallization. In a word, the crystallization rate was controlled by 〝homogeneous nucleation〞.