Large spontaneous deformation of uniaxially oriented main-chain liquid–crystalline elastomers composed of BB-n mesogens

ABSTRACT

We observed the spontaneous shape change of a uniaxially oriented liquid–crystalline elastomer composed of smectic main-chain liquid–crystalline polyesters in a cyclic heating–cooling process. Although the elastomer contracted by about 650% on heating up to the isotropic phase, the sample length recovered by about 450% on cooling to room temperature in the first heating–cooling process. In contrast, the elastomer exhibited completely reversible deformation in the second heating–cooling process. The shape change occurred with almost no change in the orientational order of mesogens in the temperature region of the liquid–crystalline phase. The mechanism of the spontaneous thermotropic shape change is discussed.

GRAPHICAL ABSTRACT

KEYWORDS:

• Chain folding
• cybotactic nematics
• liquid–crystalline elastomers
• main-chain liquid–crystalline polymers (LCPs)
• polymer networks
• shape memory
• smectic clusters
• spontaneous deformation

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the The Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (A Grant-in-Aid for Scientific Research (C) [#25410]).