Glass transition relaxation and fragility in a side-chain liquid crystalline polymer: a study by TSDC and DSC

The technique of thermally stimulated depolarisation currents (TSDC) was us ed to study the molecular dynamics in two samples of different molecular we ight of a side-chain liquid crystalline polymer. The glass transition relax ation was carefully studied in these materials using the thermal sampling p rocedure. It is suggested that the amplitude of the deviation from the zero entropy prediction is related to the fragility of the glass, and a definit ion of fragility based on the TSDC results is proposed. Results previously obtained on other side-chain liquid crystalline polymers, on the low molecu lar weight organic glass former glycerol and on the orientationally disorde red glass cyano-adamantane have also been discussed. Moreover, the physical ageing behaviour of the metastable glass below T-g was studied by the tech niques of TSDC and differential scanning calorimetry. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.