Polymerization Of Styrene Derivatives Catalyzed By Half-Sandwich Scandium Complexes

The study of catalyst systems used for homo(co)polymerization of styrene and its derivatives to synthesise functionalized polystyrene has always been a hot and difficult issue in the research of coordination polymerization. In this thesis, the relationship between catalyst structures and catalytic properties in the (co)polymerization of styrene and its derivatives is systematically analyzed. The development of new organo rare earth metal complexes have high chemical activity and selectivity, which are superior to the existing ones in (co)polymerization of styrene and its derivatives, to achieve a series of high performance functionalized polystyrene with a great potentical application.1. The catalytic activity and selectivity of polymerization of styrene derivatives are effected by the auxiliary ligands and central metal of half-sandwich scandium dialkyl complexes, the electrical property and steric hindrance of substituent group in styrene derivatives. The polymerization of styrene and styrene derivatives with electron-donating groups (NMe2, NEt2, Me) in para-position afford atactic polymers catalized by C5H5-ligated scandium complex (C5H5)Sc(CH2C6H4NMe2-O)2 (1-Sc). Howerver, the polymerization of styrene derivatives with NPh2 group affords syndiotactic polymer in the presence of 1-Sc. The polymerization of styrene, styrene derivatives with electron-donating groups (NMe2, NEt2, NPh2, Me) and electron-withdrawing groups (Cl, Br) in para-position afford syndiotactic polymers catalyzed by CsMe4SiMe3-ligated scandium complex (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 (3-Sc). The polymerization of styrene and styrene derivatives with electron-donating groups (NMe2, NEt2, NPh2, Me) in para-position afford syndiotactic polymers catalyzed by (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (4), however, the acatic polymers are obtained when the electron-withdrawing groups (Cl, Br) are in the styrene derivatives.2. By using of scandium catalyst system 1-Sc/[Ph3C][B(C6F5)4], the copolymerization of 1,3-butadiene (BD) and isoprene (IP) take place in a living, cis-1,4-selective fashion, yielding the random BD-IP copolymers with high cis-1,4 content of both monomer units. The incorporation of atactic polystyrene blocks into high cis-1,4 content BD-IP copolymers was realized in a wide range of St content (17?76 mol%) by carrying out the polymerization in the presence of the three monomers styrene (St), BD and IP with varying feed ratios. The NMR and DSC analyses suggest that the resulting copolymers are multi-block St-BD-IP terpolymers polystyrene blocks, high cis-1,4-IP (selectivity up to 98%) and high cis-1,4-BD (selectivity up to 96%) units.3. The copolymerization of styrene derivatives with conjugated dienes has been investigated in the presence of 1-Sc,3-Sc and 4 combined with one equivalent of [Ph3C][B(C6F5)4]-The copolymerization of p-methylstyrene (MeSt) with isoprene and butadiene affords MeSt-BD-IP copolymers with atactic poly(MeSt) blocks, high cis-1,4 conjugated diene catalyzed by 1-Sc, and MeSt-BD-IP copolymers with syndiotactic poly(MeSt), cis-1,4-PBD and main 3,4-PIP in the case of 3-Sc. The copolymerization of p-chlorostyrene (CISt) with isoprene and butadiene affords CISt-BD-IP copolymers with syndiotactic poly(ClSt), main 1,4-PBD and 3,4-PIP uints in the case of 3-Sc, and CISt-BD-IP copolymers with atactic poly(ClSt), main 1,4-PBD and equivalent content of 1,4-PIP and 3,4-PIP uint in the case of 4.