Koichi Ute

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.

Glass transition temperature and melting temperature of uniform isotactic and syndiotactic poly(methyl methacrylate)s from 13mer to 50mer

Abstract Highly isotactic (it-) and highly syndiotactic (st-) poly(methyl methacrylate)s (PMMAs) were fractionated into the individual homologues (uniform polymers) from the 13mer to the 50mer by means of supercritical fluid chromatography. The glass transition temperature (Tg) and crystalline melting temperature of the uniform PMMA samples were determined by differential scanning calorimetry. The Tg values of the uniform PMMAs were higher than those of the non-uniform PMMAs which are equivalent to the uniform PMMAs in tacticity, number-average molecular weight, and end-group structure. Over the molecular weight range from 1359.6 (13mer) to 5064.0 (50mer), plots of Tg against the reciprocal molecular weight (M−1) are well fitted by a linear relationship: Tg (C)= (49.6±1.3)−(4.34±0.26) × 104 M−1 for the uniform it PMMAs and Tg (C)=(123.3±1.7)−(9.38±0.33)×104 M−1 for the uniform st PMMAs with a degree of polymerization (DP)≥28 crystallized from its methanol solution by evaporation of the solvent. The reciprocal equilibrium melting temperature (Tm−1) of the crystalline uniform it PMMAs increased linearly with increasing DP−1. Extrapolation of the linear relationship gave the Tm of it-PMMA at infinite DP as 171.1 C.

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.

Quality evaluation of Angelica acutiloba Kitagawa roots by 1H NMR-based metabolic fingerprinting

The prices of Angelica acutiloba Kitagawa (yamato-toki) and A. acutiloba Kitagawa var. sukiyamae Hikino (hokkai-toki) are now mainly determined according to the sensory quality determined by experts in addition to the physical properties. This method provides a low reliability result for differentiating and qualifying their qualities. In addition, the quality in terms of pharmacological efficiency is not taken into account for consideration in the ordinary sensory method. A combination of a 1H NMR technique and a multivariate analysis was preliminarily applied for the quality evaluation of both toki roots with regard to their geographical and variety differences. A broad range of metabolites was detected by a single-run 1H NMR spectrometry. Partial least-squares discrimination analysis (PLS-DA), a pattern recognition method, was applied to the 1H NMR spectra of aqueous extracts of toki samples having different sensory qualities. The PLS-DA result showed a clear clustering corresponding to the cultivation area between toki samples cultivated in Hokkaido (Japan) and those cultivated in the southern part of China and the Nara prefecture (Japan), while there was no separation corresponding to the tokis variety and sensory qualities, indicating the inconsistency of the sensory evaluation result. The chemical metabolites contributing to the discrimination of toki samples in relation to pharmacological and sensory properties were reported for the first time. A reliable multivariate calibration model used to predict the sensory quality was successfully carried out by PLS regression.

On-line GPC/NMR experiments using the isotactic poly(methyl methacrylate) with well-defined chemical structure

SummaryGel permeation chromatography of. isotactic PMMA has been performed on a Chromatograph linked to a 500 MHz 1H NMR spectrometer. 1H NMR spectra of good resolution and high S/N ratio were collected over the entire Chromatographic peak. The Mn of the polymer sample can be directly determined by intensity measurements of the proton signals due to the endgroup and monomeric units, since the polymers used were prepared by the living polymerization initiated by t-C4H9MgBr. A good linear relation was obtained between the log(Mn) and elution time.

The occurrence of geometric polyprenol isomers in the rubber-producing plant, Eucommia ulmoides oliver

The chain length and geometric isomerism of polyprenols from Eucommia ulmoides Oliver were analyzed using supercritical fluid chromatography. After intensive effort to establish separation conditions for geometric isomers, a phenyl-bonded silica gel-packed column was found that cleanly separated poly-trans and-cis prenols. The presence of longchain poly-trans prenols (>9 mers) was confirmed for the first time in plants. Trans isomers were found in the leaf, seed coat, and root, but not in the bark and seed. Poly-trans prenols in this plant may act as intermediates for trans-polyisoprene biosynthesis.

Stereoregular oligomers of methyl methacrylate

SummaryIsotactic (it-) and syndiotactic (st-) MMA oligomers from 19-mer to 29-mer could be isolated efficiently from it-PMMA (

Structure and Biosynthesis Mechanism of Rubber from Fungi

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