Dieletric Behaviour of Poly (Vinyl Acetate) in Solution

概要

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Dielectric properties of dilute solutions of PVAc have been investigated for five samples (M^^-_n=0.79-16.34×10^4) in the frequency range of 10^6-1.5×10^8Hz. In toluene solutions, a transition phenomenon was observed at a certain temperature between -33° and 0℃, depending on molecular weight and concentration. It was also observed in carbon tetrachloride solutions between 22° and 44℃. Above the transition temperature, T_t, the relaxation time is independent of the molecular weight, while below T_t, it depends on the molecular weight. The activation energy above T_t has a small value of 3.5-4.2kcal/mole which is about a half of that below. The dipole moment for a repeat unit below T_t is by about 0.1D larger than that above. It was concluded that above T_t the molecule is in a random coil state, where the dipoles rotate freely, and a change in the conformation occurs at T_t which restricts the dipole rotation below T_t.
社団法人日本物理学会の論文
1973-05-05