Cooperative forms of molecular mobility in liquid-crystalline side-chain polymers

Dielectric behavior of LC side-chain polymers with oligomethylene spacers a nd mesogenic side groups with different structures has been investigated. N ear T-g transition, two cooperative relaxation processes, alpha and delta, were observed. Relaxation times (tau), activation energies (U), and transit ion temperatures for the alpha and delta processes were determined from log tau=phi (1/T) dependences. In the LC state these dependences are approxima ted by straight or curved lines. If the delta process is observed both in t he LC and in the isotropic state, the log tau=phi (1/T) dependences are app roximated by two lines with a break near T-cl. Kinetic parameters of the al pha and delta processes are mainly dependent on main chain structure, while the intensities are determined by parallel and perpendicular components of the dipole moment of mesogenic group.