Molecular Mobility in Liquid Crystalline Side-Chain Polyacrylates and Polymethacrylates with Cyanoazobenzene Side Groups: Dielectric Spectroscopy and Thermally Stimulated Depolarization Currents

Abstract

Molecular mobility in liquid crystalline (LC) side-chain polyacrylates and polymethacrylates with cyanoazobenzene side mesogens and methylene spacers of different lengths was investigated by dielectric spectroscopy and thermally stimulated depolarization currents methods. For both series of LC polymers, near glass transition temperature (T_g), two relaxations of cooperative character related to segmental motion (α process) and reorientation of mesogens around their short axis (δ process) are observed. Cooperativity of these processes decreases with increasing length of side chains being higher for the α process. Good correlation between dielectric spectroscopy and thermally stimulated depolarization currents methods is obtained for the temperature transitions of the α and δ processes.

Keywords:

• liquid crystaline side-chain polymers
• dielectric spectroscopy
• thermally stimulated depolarization currents
• molecular mobility
• α process
• δ process

Acknowledgments

This research has been co-financed by the European Union (European Social Fund, ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF). Research Funding Program: THALES.