Phase Transitions in Narrow Molecular Mass Samples of Side-Chain Liquid Crystalline Polymers: Molecular Mass Dependence
CASE WESTERN RESERVE UNIV CLEVELAND OH DEPT OF MACROMOLECULAR SCIENCE
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The molecular mass dependence of phase transitions in narrow molecular mass samples of smectic side-chain polyvinyl ethers is discussed in this paper with reference to earlier data by Stevens et al and Percec et al on narrow fractions of smectic side-chain polysiloxanes and polymethacrylates. The constant heat of isotropization and the proportionality between glass temperature T sub g and reciprocal degree of polymerization DP observed for polysiloxanes and polymethacrylates indicate that the order within the smectic layers and the penetration of the flexible main chains of the smectic layers was not appreciably affected by changes in DP. The polyvinyl ethers on the other hand exhibited a pronounced decrease in Delta h sub i with increasing DP and a more complex correlation between T sub g and DP indicative of an increasing disturbance by the flexible main chains of the smectic layers on increasing DP. These differences between polysiloxanespolymethacrylates and polyvinyl ethers s were also found to have profound effects on the DP dependence of the isotropization temperature.
- Polymer Chemistry