Synthesis and Characterization of Crystalline Styrene-b-(Ethylene-co-Butylene)-b-Styrene Triblock Copolymers

By merit of dual catalysis of the cationic rare-earth complex [(eta(5)-Flu-CH2-Py)Ho(CH2SiMe3)(2)(THF) (Flu=fluorenyl, Py=pyridyl) for the living polymerizations of butadiene (BD) and styrene (St), the crystalline styrene-butadiene-styrene (SBS) triblock copolymers consisting of elastic polybutadiene (PBD) sequences with suitable 1,4 regularity (about 70%) and crystalline syndiotactic polystyrene (sPS, [rrrr]>99%) sequences were successfully synthesized through sequential addition of St, BD, and St monomers. The catalytic system showed high polymerization activities for St and BD in a controlled manner. The crystalline styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymers were obtained by hydrogenation of the above SBS copolymers. The observation of a strong endothermic peak at 266 degrees C in their differential scanning calorimetry (DSC) curves confirmed the existence of the sPS blocks in the crystalline SEBS different from the industrial product Kraton SEBS-1652. Thermal degradation temperature of the crystalline SEBS (418 +/- 2 degrees C) indicated the well thermostability and process window of this polymer. (c) 2017 Wiley Periodicals, Inc.