Syndiotactic styrene-butadiene block copolymers synthesized with CpTiX3/MAO (Cp = C5H5, X = Cl, F; Cp = C5Me5, X = Me) and TiXn/MAO (n=3, X = acac; n=4, X = O-tert-Bu)

Copolymers sPS-B consisting of blocks of syndiotactic polystyrene (sPS) and polybutadiene (B) have been prepared using CpTiX3 (Cp = C5H5, X = Cl, F; C p = C5Me5, X = Me) and TiXn (n = 3, X = acetylacetonate (acac); n = 4, X = O- tert-Bu) activated with methylaluminoxane (MAO). If proper conditions ar e used, copolymers containing a range of styrene and butadiene molar tracti ons can be prepared. Structural analysis of these copolymers by means of C- 13 NMR spectroscopy allowed the assignment of different monomer diads (SS, SB, BB; S = styrene, B = butadiene) and the calculation of reactivity ratio products r(1) . r(2). Differential scanning calorimetry (DSC) analysis fur ther confirmed the block-like structure of these copolymers. The melting po ints (T-m) of syndiotactic styrene sequences decrease as the styrene molar fraction decreases, whereas the glass transition temperature (Tg) increases with decreasing butadiene molar fraction in the copolymer. The polydispers ity values ((M) over bar(w)/(M) over bar(n)) determined by GPC suggest that these copolymers are produced by a single site catalyst.