Abstract
The homopolymerization of styrene (Sty) and norbornene (NBE) was investigated in the presence of the nickel stearate (NiSt)/methylaluminoxane (MAO) catalytic system in toluene and in chlorobenzene at 20°C. The fully saturated structure of polynorbornene indicates that the two monomers polymerize by an ethylenic type addition reaction. The synthesis of true copolymers shows that one type of active species is operating for the tow monomers. Determination of reactivity ratios (rNBE = 20.8 and rSty = 0.02) indicates a much higher reactivity of NBE, which is interpreted by a coordination mechanism. The styrene-norbornene copolymers exhibit glass transition temperatures (Tg) which range from 100°C to 320°C and follow Kovacs' law. The absence of crystallinity and the homogeneous repartition of monomer units along the chains yield highly transparent materials of high thermal stability.
Published Version
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