Dielectric Chain Dynamics of Side-Chain Liquid Crystalline Polymer

Both chain dynamics and statistics of side-chain liquid crystalline polymer are experimentally explored. Dielectric measurements over a wide range of frequencies and temperature windows demonstrate that the chain dynamics in the liquid crystalline phase (SmA) is retarded and has higher apparent activation energy compared to that in isotropic melt. The molecular weight dependence of the normal mode relaxation time in the isotropic melt conforms to the Zimm model with excluded volume effect, while it shows Rouse behavior in the liquid crystalline phase. The mean squared end-to-end distance of polymer chain in the liquid crystalline phase decreases compared to that in the isotropic melt. The main chain takes a self-avoiding walk with ⟨R_e²⟩ ∼ N^2ν, ν = 0.54-0.6 in the isotropic melt, whereas a random walk between smectic layers with ν ≅ 0.5, consistent with the results from chain dynamics.