Masanao Kawabe

Syndiospecific living polymerization of 4-methylstyrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminium catalytic system

The polymerization of 4-methylstyrene with the (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe3)/tris(pentafluorophenyl)borane (B(C6F5)3)/trioctylaluminium (AlOct3) catalytic system at –20°C was carried out. The number-average molecular weight (Mn) of the polymers increased linearly with increasing monomer conversion. The propagating chain ends were successfully reacted with tert-butyl isocyanate, and the Mn of the polymer determined by 1H NMR was in good agreement with the Mn determined by GPC measurement. It is concluded that this catalytic system promoted the syndiospecific living polymerization of 4-methylstyrene.

Syndiospecific Living Block Copolymerization of Styrenic Monomers Containing Functional Groups, and Preparation of Syndiotactic Poly{(4-hydroxystyrene)-block-[(4-methylstyrene)-co-(4-hydroxystyrene)]}

At -25 °C, the sequential block copolymerizations of 4-(tert-butyldimethylsilyloxy)styrene (TBDMSS) and 4-methylstyrene (4MS) were investigated by using a syndiospecific living polymerization catalyst system composed of (trimethyl)pentamethylcyclopentadienyltitanium (C p *TiMe 3 ), trioctylaluminum (AlOct 3 ) and tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ). The number-average molecular weight (M n ) of the poly(TBDMSS)s increased linearly with increasing the polymer yield up to almost 100 wt.-% consumption of TBDMSS used as 1 st monomer. The M n value of the polymer after the second monomer (4MS) addition continued to increase proportionally to the polymer yield. The molecular weight distributions (MWDs) of the polymers remained constant at around 1.05-1.18 over the entire course of block copolymerization. It was concluded that the block copolymerizations of TBDMSS and 4MS with the C p *TiMe 3 /B(C 6 F 5 ) 3 /AlOct 3 catalytic system proceeded with a high block efficiency. The 13 C NMR analysis clarified that the block copolymers obtained in this work had highly syndiotactic structure. By the deprotection reaction of silyl group with conc. hydrochloric acid (HCl), syndiotactic poly{(4-hydroxystyrene)-block-[(4- methylstyrene)-co-(4-hydroxystyrene)]} (poly[HOST-b- (4MS-co-HOST)]) was successfully prepared.

Solvent Effect on β-Hydride Elimination Reaction in Syndiospecific Styrene Polymerization with Cyclopentadienyltitanium Trichloride (CpTiCl3)/Methylalumoxane (MAO) Catalytic System

The influence of the type of solvent on styrene polymerization behavior with cyclopentadienyltitanium trichloride (CpTiCl 3 ) and methylalumoxane (MAO) catalytic system at 25°C was investigated. It was found that the number-average molecular weight (M n ) of the polystyrene produced was correlated with the dielectric constant of solvent (e). The maximum M n was obtained by using the solvents having proper dielectric constant at e = 4.0-4.2. The kinetic analyses and 1 H NMR measurements strongly suggested that this solvent effect was induced by the decrease of rate constant of β-hydride elimination (K tr β ). The correlation between the kinetic parameters and the dielectric constant of solvent suggests competitive equilibrium between coordination of solvent and β-agostic interaction should exist.

Synthesis of Block Graft Copolymer with Syndiospecific Living Polymerization of Styrene Derivatives by (Trimethyl)pentamethylcyclopentadienyltitanium/Tris(pentafluorophenyl)borane/Trioctylaluminium Catalytic System

Two kinds of syndiotactic AB type block copolymers were prepared, which were (1) poly(4-methylstyrene)-block-polystyrene {Poly(4MS-b-S), (A: poly(4MS), B: polystyrene (S))}, (2) poly(4-methylstyrene)-block-poly(styrene-co-3-methylstyrene) {poly[4MS-b-(S-co-3MS)] (A: poly(4MS), B: styrene/3-methylstyrene (3MS) copolymer)}. For the syntheses of these diblock copolymers, the living polymerization catalytic system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe3) premixed with trioctylaluminium (AlOct3), and tris(pentafluorophenyl)borane (B(C6F5)3) was used at –25°C. Chlorination of the methyl groups of poly[4MS-b-(S-co-3MS)] was conducted by aqueous sodium hypochlorite (NaOCl) and phase-transfer catalyst such as tetrabutylammonium hydrogensulfate (TBAHS). The novel tapered densely grafted diblock copolymer was synthesized with by coupling reaction of living poly(2-vinyl pyridine)lithium (Poly(2VP)Li) with the partly chloromethylated poly[4MS-b-(S-co-3MS)].