Temperature effects in hydrodynamic properties of comb-like polymer with laterally attached mesogenic units

The specific temperature effects in hydrodynamic properties (intrinsic visc osity, sedimentation velocity and translational diffusion) of side-on comb- like polymers with molecular weights from 5.70 x 10(5) to 3.02 x 10(6) were observed in dilute solution in two different solvents, benzene and chlorof orm, over a temperature range from 2 to 73 degrees C. The viscosity tempera ture coefficient dln[eta]/dT was found to be negative in sign in chloroform (- 0.007 K-1) and positive in benzene (+ 0.005 K-1). Increase in temperatu re leads to intensification of the excluded volume effects in real benzene solution of the polymer and to weakening of those in chloroform. Simultaneo usly, increase in temperature leads to decreasing unperturbed dimensions of the macromolecule chain in both the solvents. This effect is more pronounc ed in benzene (dln(h(2))/dT = - 0.005 K-1, where [h(2)] is the mean-square end-to-end distance) than in chloroform ( - 0.001 K-1). Origins of the temp erature effects are discussed with relation to the lateral structure of the macromolecule where every monomer unit contains the threecyclic mesogenic moiety which is laterally (with the middle part) attached to a side chain c onsisting of 11 carbon atoms. (C) 1999 Published by Elsevier Science Ltd. A ll rights reserved.