Tatsuki Kitayama

Stereoregular polymerization of α-substituted acrylates

Abstract This article reviews recent investigations on the stereospecific polymerization and oligomerization of α-substituted acrylates by radical and anionic initiators, including the preparation of highly isotactic and syndiotactic PMMAs and also a heterotactic PMMA. Side reactions in the anionic polymerizations by organolithium and -magnesium compounds are discussed in detail. Matrix and plasma polymerizations, group transfer polymerization and preparation of macromonomers are reviewed from the viewpoint of stereoregularity. Tacticity dependence of properties and reactivity of polymethacrylates and polyacrylates, as well as recent developments in the analysis of tacticity of polymethacrylates, are also described.

Highly syndiotactic poly(methyl methacrylate) with narrow molecular weight distribution formed by tert-butyllithium-trialkylaluminium in toluene

SummaryPolymerization of MMA with t-C4H9Li in toluene in the presence of trialkylaluminum(alkyl=methyl, ethyl, butyl, isobutyl, and octyl) was examined at various Al/Li ratios. Triethyl-, tributyl and trioctylaluminums worked quite effectively in the polymerization to give highly syndiotactic PMMA with narrow molecular weight distribution (MWD) at the Al/Li ratio of 3 and higher than 3. The highest syndiotacticity of 96% was attained with t-C4H9Li/(n-C8H17)3Al (1/3) at −93°C. The polymerization was initiated by t-C4H9 anion and proceeded in a living manner. The structure of the syndiotactic PMMA is chemically identical to that of isotactic PMMA prepared with t-C4H9MgBr. Consequently, highly isotactic and syndiotactic PMMAs with narrow MWD and with the same chemical structure from α-end to ω-end were obtained.

Synthesis and properties of poly(ether ether ketone)-poly(ether sulfone) block copolymers

Two series of block copolymers composed of poly(ether ether ketone) (PEEK) and poly(ether sulfone) (PES) components were prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction. In the first series of block copolymers, the Mn of the PEEK segment was fixed at 10 000, while the Mns of the PES segments ranged from 250 to 9330. (The PES contents of the copolymers varied from 2.2 to 46.2%.) For the other series of block copolymers, the compositions were kept almost constant (PES content ∼36%), while the segment lengths were changed. Various properties of the copolymers were investigated by differential scanning calorimetry (d.s.c.), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (t.g.a.), and dynamic mechanical analysis (d.m.a.). The results showed that the copolymers exhibited no phase separation and the relationship between the glass transition temperature and the compositions of the copolymers approximately followed the formula, Tg = Tg1W1 + Tg2W2. The crystallization behaviour, thermal properties and dynamic mechanical behaviour of the copolymers were investigated and it was found that both the PES content and the segment length of the copolymers had a significant influence on their crystallization behaviour.

DEFINITIONS OF TERMS RELATING TO REACTIONS OF POLYMERS AND TO FUNCTIONAL POLYMERIC MATERIALS (IUPAC Recommendations 2003)

The document defines the terms most commonly encountered in the field of polymer reactions and functional polymers. The scope has been limited to terms that are specific to polymer systems. The document is organized into three sections. The first defines the terms relating to reactions of polymers. Names of individual chemical reactions are omitted from the document, even in cases where the reactions are important in the field of polymer reactions. The second section defines the terms relating to polymer reactants and reactive polymeric materials. The third section defines the terms describing functional polymeric materials.

Preparation of highly isotactic and syndiotactic poly(methyl methacrylate) macromonomers having the same chemical structure and their polymerization

SummaryHighly isotactic living poly(methyl methacrylate) (PMMA) anion prepared with t-C4H9MgBr in toluene at −78°C reacted quantitatively with p-bromomethylstyrene (p-BMST) in the presence of hexamethylphosphoramide or 1,8-diazabicyclo[5.4.0]-undec-7-ene to give the PMMA macromonomer with narrow molecular weight distribution. Highly syndiotactic PMMA macromonomer was also prepared by the reaction of p-BMST and the living PMMA anion formed by t-C4H9Li-(n-C4H9),Al (Al/Li=3) initiation in the presence of tetramethylethylenediamine. Radical polymerization and copolymerization of these macromonomers were studied in some detail. The results showed the higher reactivity of the isotactic PMMA macromonomer than the syndiotactic one.

Separation of poly(methyl methacrylate)s according to their tacticity

SummaryThe unconventional liquid chromatography of polymers under limiting conditions of their solubility was applied to poly(methyl methacrylate)s differing in their tacticity. The polymers were dissolved in thermodynamically good solvents and injected into an appropriate size exclusion chromatographic (SEC) column flushed with matched, moderately strong nonsolvents. The set of (limiting) conditions was found under which less soluble syndiotactic poly(methyl, methacrylate) moved along the column together with the zone of its initial solvent while better soluble isotactic poly(methyl methacrylate) was eluted according to the SEC mechanism. This indicates the potential of liquid chromatography under limiting conditions to characterize the tacticity of poly(methyl methacrylate)s.

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.

REMARKABLE EFFECT OF STRUCTURE OF BULKY ALUMINUM PHENOXIDES ON STEREOSPECIFICITY OF METHACRYLATE POLYMERIZATION

Abstract Polymerizations of methyl methacrylate and ethyl methacrylate with combinations of t-butyllithium and several bulky alkylaluminum bisphenoxides were carried out in toluene at −78°C. Methylaluminum bisphenoxide derivatives gave heterotactic polymers which comprise an alternating sequence of meso and racemo diads. On the other hand, ethyl or isobutylaluminum bis(2,6-di-t-butylphenoxide) exhibited syndiotactic-specificity. The effect of structure of bulky aluminum phenoxide on stereospecificity of polymerization was discussed based on the stereochemical analysis of the polymers.

Stability and Degradation of Polymethacrylates with Controlled Structure

Abstract Thermal degradation behaviors for homo- and copolymers of methacrylates prepared by stereospecific living polymerizations as well as radical polymerization were studied. Thermal stability of radically prepared PMMAs can be improved by careful control of end groups and by incorporation of methyl acrylate into the chain. The mechanism of the stabilization was elucidated. Tacticity dependence of thermal stability of PMMAs was examined using isotactic and syndiotactic PMMAs with molecular weights ( M n ) of 2,500–500,000 under nitrogen. Syndiotactic PMMAs showed higher degradation temperatures than the isotactic PMMAs of the same M n when the M n was lower than 25,000, and vice versa for the higher M n . A similar M n and tacticity dependence was observed in degradation in air, and the critical M n was found to be about 10,000. These phenomena are discussed in terms of zip length of degradation and the difference in flexibility between isotactic and syndiotactic PMMA chains. Thermal degradation behav...

9: Definitions of Terms Related to Polymer Blends, Composites, and Multiphase Polymeric Materials (2004)

The document defines the terms most commonly encountered in the field of polymer blends and composites. The scope has been limited to mixtures in which the components differ in chemical composition or molar mass and in which the continuous phase is polymeric. Incidental thermodynamic descriptions are mainly limited to binary mixtures although, in principle, they could be generalized to multicomponent mixtures. The document is organized into three sections. The first defines terms basic to the description of polymer mixtures. The second defines terms commonly encountered in descriptions of phase domain behavior of polymer mixtures. The third defines terms commonly encountered in the descriptions of the morphologies of phase-separated polymer mixtures. Reproduced from: Pure Appl. Chem., Vol. 76, No. 11, pp. 1985–2007, 2004.