Syndiospecific Synthesis of Longer <i>p-n-</i>Alkyl<i>-</i>Substituted Polystyrenes Using Monocyclopentadienyl-Type Titanium Catalysts

Abstract

Substituted styrenes with linear alkyl substituents (C 6 to C 12 ) at the para position on the ring were synthesized and polymerized using the (Me) 5 CpTi(OMe) 3 /MAO catalytic system. Increased polymerization activities were observed for longer alkyl group (>C 6 ) substituted styrenes; all resulting polymers were highly syndiospecific (>99% rr) regardless of alkyl chain lengths. Syndiotactic poly( p -alkylstyrene)s were characterized by SEC, 1 H and 13 C NMR, DSC, and X-ray diffraction. No melting transition was observed for polymers prepared from p -methyl-, p - n -hexyl, and p - n -octylstyrenes. Side-chain-induced crystallization was observed for linear C 10 and C 12 alkyl-substituted polystyrenes ( T m ≈ 90 °C). The T g decreased with an increase in the length of alkyl side chain up to C 8 length; above C 10 side-chain length, the T g slightly increased. The T g 's of syndiotactic poly( p - n -alkylsyrene)s were significantly higher than those reported for the corresponding nontactic analogues.