Synthesis and Characterization of Syndiotactic Styrene−Ethylene Block Copolymers

Abstract

Six samples of styrene−butadiene block copolymers (sPS−B 1−6) containing a range of styrene molar fractions (xS = 0.9−0.16) were prepared using MAO-activated CpTiCl3 and converted to the corresponding styrene-1-butene-ethylene terpolymers (sPS−PE, 1h−6h) through the selective hydrogenation of the unsaturated butadiene segments with p-toluenesulfonhydrazide. The monomer compositions and chemical microstructures of the sPS−PE copolymers were determined by 1H NMR (xS = 0.93−0.1) and 13C NMR, respectively. The chemical shift assignments of the monomer tetrads (SSSS, SSEE, EESE, EEbE, EEEE, SEES, EEES; S = styrene, E = ethylene, b = 1-butene) were also determined by 13C NMR as well as the average monomer block lengths (nS = 72−4; nE = 2−51). The block structure of the sPS−PE copolymers was further confirmed by DSC (differential scanning calorimetry), WAXD (wide-angle X-ray diffraction), and solid-state CP-MAS 13C NMR (cross polarization magic angle spinning) analysis. The sPS−PE samples with high styrene conte...