Dielectric relaxation in poly(styrene-b-butadiene) copolymers with perfluorinated side chains

The dynamics of several poly(styrene-b-butadiene) (PS-PB) copolymers with f luorocarbon side chains have been studied with dielectric spectroscopy, cov ering two different mesophases with long spacings between 10 and 30 nm, and two different tail lengths. It is found that fluorination results in compa rably rigid side chains in the PB domains with highly anisotropic propertie s. In the glassy state an Arrhenius relaxation was found with an activation energy of 7.4 kcal/mol reflecting some local side chain relaxation. Above the PB glass transition a bimodal relaxation exists, comprising two coopera tive processes reflecting solely the anisotropic dynamics of the side chain . The dual relaxation resembles the anisotropic dielectric properties of si de chain liquid crystalline polymers in the absence of macroscopic orientat ion. (C) 2000 American Institute of Physics. [S0021-9606(00)50832-0].