Local intramolecular mobility in linear polyesters simulating the structure of thermotropic polymers

Local intramolecular mobility in regular linear polyesters with flexible si loxane and more rigid ester aromatic fragments providing in some cases LC s tate was studied by dielectric spectroscopy. The dielectric transitions rel ated to the local mobility in the ester aromatic fragment were observed. It was shown that two local relaxation processes (beta' and beta ") with diff erent mechanisms of mobility took place in these systems. One of them, the beta " process. having the shortest relaxation times (tau similar to 10(-7) s) is connected with the motion of ester groups and phenyl rings. It is de termined only by intramolecular interactions. The second local process, bet a', reflects the motion of the polar ester group including the central part of the ester aromatic fragment (tau similar to 10(-1)-10(-4) s). This moti on can be realized at the beginning of flipping of the aromatic ring. Param eters of the beta' process depend on intra- and intermolecular interactions . (C) 1999 Elsevier Science Ltd. All rights reserved.