LOCAL CHAIN DYNAMICS OF POLY(CIS-1,4-ISOPRENE) IN DILUTE-SOLUTIONS STUDIED BY THE FLUORESCENCE DEPOLARIZATION METHOD

Local segmental motions of poly(cis-1,4-isoprene) (cis-PI) labeled with anthracene were examined by the method of fluorescence depolarization using 1,4-dioxane, n-dodecane, cyclohexane, benzene, ethylbenzene, and o-xylene as the solvents with a viscosity of less than 2cP. The anisotropy ratio was measured in these dilute solutions, and the mean relaxation time, T-m, for the chain local motion was obtained. The activation energy, E*, was obtained by using the theory of Kramers' diffusion limit. The reduced relaxation time, T-m/eta, for cis-PI was much shorter than that for polystyrene and was independent of the local segment density differing from that of polystyrene. The dependence of activation energy, E*, on the solvent was very weak, compared to that of polystyrene. These findings could be interpreted in terms of the dynamic flexibility of the polymer chain.