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) |
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Authors: | Adolfo Zambelli Michela Caprio Alfonso Grassi Daniel E. Bowen |
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Abstract: | Copolymers sPS‐B consisting of blocks of syndiotactic polystyrene (sPS) and polybutadiene (B) have been prepared using CpTiX3 (Cp = C5H5, X = Cl, F; Cp = C5Me5, X = Me) and TiXn (n = 3, X = acetylacetonate (acac); n = 4, X = O‐tert‐Bu) activated with methylaluminoxane (MAO). If proper conditions are used, copolymers containing a range of styrene and butadiene molar fractions can be prepared. Structural analysis of these copolymers by means of 13C NMR spectroscopy allowed the assignment of different monomer diads (SS, SB, BB; S = styrene, B = butadiene) and the calculation of reactivity ratio products r1·r2. Differential scanning calorimetry (DSC) analysis further confirmed the block‐like structure of these copolymers. The melting points (Tm) 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 polydispersity values (Mw/Mn) determined by GPC suggest that these copolymers are produced by a single site catalyst. |
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