We report on the dielectric normal mode relaxation of the isoprene block chains in dilute and semidilute solutions of butadiene–isoprene (BI) diblock copolymers and butadiene–isoprene–butadiene (BIB) triblock copolymers. The dielectric loss ε'' curves in dilute solutions with a concentration close to the overlapping concentration C* agreed approximately with those predicted by the bead–spring model. Above a concentration about three times higher than C*, the ε'' curves broadened with increasing concentration indicating the strong concentration dependence of the distribution of the normal modes. Two maxima of the ε'' curves were observed for BIB solutions. In semidilute solutions of BIB, the ε'' peak located in the high frequency side shifted little with concentration but the ε'' peak in the low frequency side shifted towards low frequency with increasing concentration. This suggests that the lower order normal modes are affected by entanglement effects but the higher order modes are not, for semidilute solutions. We have attempted to explain the distribution of the normal modes in terms of the blob model.
Посилання на статтю:
Dielectric study of dynamics of subchains and distribution of normal mode relaxation times in dilute and semidilute solutions of miscible block copolymers / Keiichiro Adachi, Hitotsugu Hirano, Juan J. Freire // Polymer. – 1999. – N 40. – P. 2271–2279.