Birefringence thermal analysis of liquid crystalline monomers and their photopolymers

Birefringence analysis was used to measure thermal transitions in liquid crystal diacrylate monomers and their corresponding polymers. In this technique, linearly polarized light was used to probe the sample as the temperature increased via a linear ramp. Various phase transitions were observed in the liquid crystalline monomers. In addition, the monomers were isothermally photopolymerized in the liquid crystalline state and the resulting polymer networks retained their liquid crystalline order. Glass-to-rubber transitions as well as indications of further thermal polymerization and stress relaxation were detected. Results from birefringence experiments were compared to those of more traditional thermal analysis techniques including DSC and TMA.The authors would like to thank the National Science Foundation for sponsoring this research under NSF Grant No. DMR-9420357. We would also like to thank Mary Galaska and John Murphy, of the University of Dayton, for their help in conducting experiments, and Katy Weaver, also of the University of Dayton, for her help in sample preparation.