ポリマーにおける分子内回転と核磁気共鳴

抄録

Nuclear magnetic rosonance absorption measurements are reported for polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyvinyl acetate (PVAc), polymethacrylic acid, poly-n-butyl methacrylate, and their monomers, in the temperature range from -170 to 100°C.
It has recently been pointed out that methyl groups in PMMA are not active in re-orientating around C₃ axis at room temperature in contrast with the ones in molecular crystals. Results obtained on PMMA, PMA, and PVAc confirm that all methyl groups are not in freely rotational state below the temperature at which the main line narrowing occurs.
However, it should be noted that, in poly-methacrylic acid and poly-n-butyl methacrylate, the methyl groups seem to rotate fast enough at room temperature, and that in the crystalline state of methyl methacrylate and methyl acrylate monomers, the methyl group rotates freely even in the neighbourhood of -150°C.
In each case of PMA and PVAc, the “anomalous narrowing” is found in lower temperature region. This phenomenon seems to be similar to the one that is found in PMCA.
Observed line narrowing in PMA and PVAc is correlated satisfactorily with known dielectric and mechanical properties of the materials.
Lastly, interpretations of the rotational states of groups in polymers are given.