Synthesis of Well-Defined Halogenated Styrenic (CO)polymers: Polymerisation Catalyzed by Half-Titanocenes and Their Post-Modification

Abstract

Well-defined halogenated syndiotactic polystyrenes and ethylene/styrene copolymers were synthesized by 1) coordination polymerisation of p-trimethylsilylstyrene (p-TMSSt) using half-titanocene catalysts and 2) subsequent post-modification under mild conditions. Syndiospecific styrene polymerisation of p-TMSSt using a (Me3SiC5H4)TiCl2(O-2,6-iPr2C6H3) (7)−MAO system yielded high-molecular-weight polymers with a unimodal distribution as well as exclusive syndiotactic stereo-regularity (>99%). Ethylene copolymerisation with p-TMSSt using the 7– and (tBuC5H4)TiCl2(O-2,6-iPr2-4-SiEt3-C6H2) (2)–MAO systems also yielded high-molecular-weight polymers, ranging from 73,800 to 292,000 (Mw/Mn = 1.88–2.27). Ethylene copolymers with high p-TMSSt contents (>50 mol%) were also prepared. Exclusive halogenation of the silylated polymers was achieved by silicon–halogen exchange using iodine chloride or N-bromosuccinimide to produce poly(iodostyrene)s or poly(bromostyrene)s, respectively. Thus, various functionalized polystyrenes have been prepared from poly(iodostyrene)s via cross-coupling reactions. In addition, the ethylene copolymers showed promising elastic properties; the elongation, tensile strength, toughness, and self-healability could be tuned by varying the comonomer content and aromatic substituents.