Mesomorphic Properties of Main-Chain Chiral-Smectic Elastomers Cross-Linked in Different Phases

Abstract

We investigate the mesomorphic properties of main-chain chiral-smectic elastomers cross-linked in different phases, analyzing three samples prepared by photo-cross-linking a chiral smectic C (SmC*) polymer in the SmC*, SmA, and isotropic (Iso) phases. The SmC*-cross-linked elastomer exhibits successive SmC*-SmA-Iso transformations similarly to the precursor polymer. However, only the orthogonal molecular alignment due to the SmA structure appears in the SmA-cross-linked elastomer. Moreover, isotropic alignment remains in most of the Iso-cross-linked elastomer even at room temperature. Since the effect of the fixed orientation is not localized in the vicinity of cross-links because of the direct coupling between the mesogenic orientation and the polymeric conformation in main-chain smectic elastomers, the transformation from the cross-linked phase to a higher-order phase might be forbidden.

Keywords:

• Chiral
• elastomers
• helix
• liquid-crystalline polymers (LCP)
• main-chain
• polymer networks
• spiral
• X-ray

Acknowledgments

We thank Professor Dr. Junji Watanabe and Professor Dr. Masatoshi Tokita for their advice on the synthesis of the BB-n polymers and networks. We also thank Ihara Chemical Co., Ltd. for kindly supplying p,p’-bibenzoate. This work was supported by a Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).