Crystallization behavior of poly(styrene-ethylene) copolymers prepared by sequential polymerization

Polystyrene-ethylene copolymers were prepared by sequential polymerization of styrene and ethylene. The crystallization behaviors of the PSE copolymers were studied by polarized light microscopy, wide angle X-ray diffraction and differential scanning calorimeter. The spherulitic growth rates have a tendency of reduction with increasing of styrene content. The growth rates, the melting points and onset temperatures of melting peaks are lower than those of pure polyethylene. The orthorhombic lattice parameters of relatively low styrene content are slightly larger than those in pure PE and the X-ray diffraction traces are no more typically orthorhombic when the styrene content is relatively high. The DSC analyses on the annealed fractions extracted with temperature gradation elution fractionation revealed that the components in the copolymer could be classified into three types based on the thermal behaviors: styrene ethylene random copolymer, ethylene-predominant copolymer and multi-ethylene segment copolymer.