6533b85afe1ef96bd12b9ed7

RESEARCH PRODUCT

Differences between smectic homo‐ and co‐polysiloxanes as a consequence of microphase separation

subject

description

This paper compares smectic phases formed from LC‐homo‐ and LC‐co‐polysiloxanes. In the homopolysiloxane, each repeating unit of the polymer chain is substituted with a mesogen, whereas in the copolysiloxanes mesogenic repeating units are separated by dimethylsiloxane units. Despite a rather similiar phase sequence of the homo‐ and co‐polysiloxanes—higher ordered smectic, smectic C* (SmC*), smectic A (SmA) and isotropic—the nature of their phases differs strongly. For the copolymers the phase transition SmC* to SmA is second order and of the ‘de Vries’ type with a very small thickness change of the smectic layers. Inside the SmA phase, however, the smectic thickness decreases strongly on approaching the isotropic phase. For the homopolymer the phase transition SmC* to SmA is first order with a significant thickness change, indicating that this phase is not of the ‘de Vries’ type. This difference in the nature of the smectic phases is probably a consequence of microphase separation in the copolymer, which ...