105.立体規則性ポリメチルメタクリレイトの双極子モーメント

概要

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Iso-PMMA was prepared by using t-C_4H_9MgBr as the initiator in toluene at -60℃ and syn-PMMA, by t-C_4H_9Li-(C_2H_5)_3Al in toluene at -78℃. Their tacticities determined by NMR measurements are mm=97% (isotactic triad) and rr=87% (syndiotactic triad), respectively. Dipole moments of the PMMA samples were determined from measurements of the dielectric constants and densities in dilute benzene solution at seven different temperatures ranging from 25 to 55℃. The dipole moments of the PMMAs and their temperature dependence showed a marked difference depending on the tacticity of the samples; the iso-PMMA gives greater values of the dipole moment (μ) than those for the syn-PMMA, and with increasing temperature, the μ value of the iso-PMMA showed little change, but that of the syn-PMMA continuously increased; e.g. 1.457D (25℃) and 1.460D (55℃) were obtained for the iso-PMMA, and 1.323D (25℃) and 1.399D (55℃) for the syn-PMMA. The comparison of the experimental results with the calculated ones leads to a conclusion that the difference in the μ values between the iso- and syn-PMMA could be interpreted as due to different conditions for the internal rotations of polar side groups in the iso- and syn-PMMA chains.
東京女子大学の論文
1994-03-15