Dielectric Normal and Segmental Modes in Undiluted Poly(butylene oxide)

Dielectric measurements were carried out on undiluted poly(butylene oxide) (PBO) with various molecular weights. The dielectric normal mode relaxation due to fluctuation of the end-to-end vector and the segmental relaxation due to local motions were observed. The relaxation time τ n for the normal mode and τ s for the segmental mode conformed to the Vogel−Fulcher equation, and the ratio of τ n /τ s did not depend on temperature. From the relaxation strengths for the normal and segmental modes, the parallel and perpendicular components of the dipole moment were determined. With the aid of the literature data of the end-to end distance, the dipole moment per unit contour length of PBO chains was also determined. It was found that the M dependence of τ n changed around the characteristic molecular weight M c (=6000), i.e., in the range of M < M c, τ n is proportional to M 2.0, and in the range M > M c τ n is proportional to M 3.4 . The relationship between the segmental dynamics and chain dynamics is discussed.