Koichi Hatada

Structurally controlled polymerizations of methacrylates and acrylates

Progress in the structure control of polymethacrylates and polyacrylates through stereospecific living polymerization are described. Three types of stereospecific living polymerizations have been developed for methacrylate polymerization: isotactic with t-C4H9MgBr, syndiotactic with xadt-C4H9Li/R3Al, and heterotactic with t-C4H9Li/bis(2,6-di-t-butylphenoxy)methylaluminium [MeAl(ODBP)2]. The last initiator system has been proved effective for monomer-selective living copolymerization of methacrylates. The living nature of these polymerizations allows extensive use for the syntheses of stereoregular block polymers and copolymers, and end-functionalized polymers such as macromonomers. Through stereospecific polymerizations and copolymerizations of macromonomers, comb polymers and graft copolymers with defined stereoregularities in the main chain and side chains could be obtained. Some properties of these stereoregular polymers are also described, including stereocomplex formation and solution viscosity. Stereospecific polymerizations of crotonates leading to diisotactic, diheterotactic and disyndiotactic polymers are also discussed. Supercritical fluid chromatography (SFC) has been proven to be useful for isolating uniform polymers from stereoregular poly(methyl methacrylate)s (PMMAs) with narrow molecular weight distribution. Uniform end-functionalized polymers have been used to construct more elaborate uniform polymer architectures such as stereoblock, star, and comb polymers, and copolymers. The uniform polymers have been proven quite useful for the studies of the relationship between structures and properties such as glass transition temperature, melting temperature and solution viscosity. Particularly interesting is the use of isotactic and syndiotactic uniform PMMAs for the understanding of stereocomplex formation in certain solvents such as acetone. Furthermore, a uniform stereoblock PMMA was found to undergo intramolecular complexation in addition to intermolecular complexation in acetone. Uniform star and comb PMMAs were also prepared and found useful for discussing the effect of branching on the solution viscosity. n n n n© 2000 Society of Chemical Industry

Living polymerization of primary alkyl acrylates with t-butyllithium/bulky aluminum Lewis acids

Anionic polymerizations of primary alkyl acrylates such as ethyl acrylate (EA) and n-butyl acrylate (n-BuA) with tert-butyllithium (t-BuLi) in the presence of bis(2,6-di-tert-butylphenoxy)alkylaluminums were carried out in toluene. The polymerizations with t-BuLi/bis(2,6-di-tert-butylphenoxy)ethylaluminum at low temperatures gave syndiotactic-rich polymers with narrow molecular weight distribution (MWD) in high yields, while those with t-BuLi/bis(2,6-di-tert-butylphenoxy)methylaluminum gave polymers with broader MWD in lower yields. The monomer addition experiment revealed the livingness of the former polymerizations. The initial monomer concentration and polymerization temperature were found to affect the MWD and the stereoregularity of the obtained polymers.

PREPARATION OF STAR-SHAPED POLYMER WITH STEREOREGULAR POLY(METHYL METHACRYLATE) ARMS

ABSTRACT Isotactic (it-) PMMA anions prepared with t-C4H9MgBr in toluene were reacted with ethylene glycol dimethacrylate (EGDMA) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to obtain a star shaped polymer. 1H NMR, SEC-LALLS and SEC-differential viscometric analyses of the polymer clearly indicated that the polymer is a highly branched star polymer with crosslinked dimethacrylate core; the number of arms was estimated to be 20–30. A similar reaction of syndiotactic (st-) PMMA anions formed with t-C4H9Li-(n-C4H9)3Al in toluene with EGDMA was unsuccessful. However, the use of butane-1,4-diol dimethacrylate instead of EGDMA resulted in the effective formation of star polymers having st-PMMA arms; the number of arms was estimated to be 139. As a result, two types of star -shaped polymethacrylates with it- and st-PMMA arms were obtained.

Revised patterns of reactivity scheme. VII. Revised patterns scheme and its relationship to carbon-13 NMR spectra

The electron density on a carbon atom determines the 13C chemical shift observed in the NMR spectrum. In a vinyl monomer, the same electron density must contribute strongly to polar effects involved in the addition of a radical to that monomer and possibly in the addition (to a double bond) of a radical terminated by a unit derived from that monomer. It is shown that the expected correlation exists when the polar effects in polymerization reactions are represented by the parameters of the revised patterns scheme.

Feature Article: Heterotactic Polymers of Methacrylates and Their Properties

Abstract Heterotactic (ht-) polymer is a kind of stereoregular polymer, which consists of an alternate arrangement of meso (m) and racemo (r) diads. Heterotactic polymerization requires a higher order of stereocontrol than isotactic and syndiotactic polymerizations, because opposite stereoselectivities, m-addition and r-addition, have to occur in an alternate manner for the formation of ht-sequence, …mrmrmr…. We have succeeded in preparing highly heterotactic polymers with mr contents over 90% by a living polymerization of methacrylates with t-C4H9Li and bis(2,6-di-t-butylphenoxy)methylaluminum. Mechanism of the stereoregulation was discussed with the aid of NMR and supercritical fluid chromatographic analyses of the stereoregularity both at in-chain and chain-ends. Some properties of ht-polymethacrylates are also described.

Carbon-13 NMR Spectra of Stereoregular Copolymers of Methyl and Butyl Methacrylates

Abstract Highly isotactic and syndiotactic copolymers of methyl methacrylate (MMA) and butyl methacrylate (n-BuMA) with random monomer sequence distribution were prepared in toluene at -78°C with t-C4H9MgBr and t-C4H9Li/(C2H5)3Al, respectively. 13C NMR spectra of carbonyl region of the copolymers were measured in chlorobenzene-d 5 at 115°C and 125 MHz and analyzed in regard to both monomer sequence and configurational sequence distributions. 13C NMR spectra of radically prepared poly(MMA-ran-n-BuMA)s were also analyzed based on the assignments established by the analysis of the spectra of the stereoregular copolymers.