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

The dynamics of several poly(styrene-b-butadiene) (PS-PB) copolymers with fluorocarbon side chains have been studied with dielectric spectroscopy, covering two different mesophases with long spacings between 10 and 30 nm, and two different tail lengths. It is found that fluorination results in comparably rigid side chains in the PB domains with highly anisotropic properties. 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 cooperative processes reflecting solely the anisotropic dynamics of the side chain. The dual relaxation resembles the anisotropic dielectric properties of side chain liquid crystalline polymers in the absence of macroscopic orientation. (C) 2000 American Institute of Physics. [S0021-9606(00)50832-0].