Nobuo Miyatake

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.

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 (

Isotactic and Syndiotactic Pentacontamers (50mers) of Methyl Methacrylate Obtained by Fractionation with Preparative SFC: The GPC Analysis of the 50mers and Their Stereocomplex.

\overline {DP}

Synthetic uniform polymers and their use in polymer science

= 28.6) and st-PMMA (

Controlled Synthesis of Isotactic and Symmetrical Poly(methyl methacrylate) Directed toward Uniform Polymers with High Crystallinity

\overline {DP}

Conformational Asymmetry of a Linear Perfluoroalkyl Chain in Solution. Dynamic Fluorine-19 NMR Spectroscopy of the Perfluoro-n-alkanes Carrying a Chiral End-Group as a Probe of Magnetic Nonequivalence

= 28.6) (sample load: 50 mg) by the SFC using a 10 mm i. d. x 250 mm column packed with silica gel. DP of each isolated oligomer was determined by FD mass spectroscopy, and the values agreed well with those calculated from the relative intensity of 1H NMR signals due to CH3O- and the terminal t-C4H9-groups. Glass transition temperature (Tg) of the it-28-mer measured by DSC was 34.5°C, which was higher than that of the it-PMMA by 6.5°C. Tg of both the it-and st-oligomers increased linearly with DP in the range of DP=20∼29. A 1: 1 mixture of the it- and st-27-mers annealed at 140°C showed an endothermic transition at 102.3°C which was attributable to melting of stereocomplex, whereas an annealed 1: 1 mixture of the it- and st-PMMAs had a much broader endotherm around 80∼140°C.