Vapour-Induced Liquid Crystallinity and Self-Recovery Mechanochromism of Helical Block Copolymer

New molecular design of conjugated polymer that possess high sensitivity to vapour and self-recovering property against pressure is proposed. We synthesised a rod-rod diblock copolymer, poly(3-((3S)-3,7-dimethyl-octyl)-thiophene)-block-poly(4-octyl phenylisocyanide) (PTh- b -PPI), composed of a π-conjugated polymer and a rod-type helical coiled polymer. Introduction of PPI block in the block copolymer architecture enabled PTh- b -PPI film to exhibit solid-to-liquid crystal phase transition by exposure to chloroform vapour, accompanied with colour change (purple-to-yellow), which is the first report on a new phenomenon of "vapour-induced liquid crystallinity". In addition, PTh- b -PPI film showed colour change (purple-to-vermillion) during mechanical shearing, and spontaneously recovered under ambient conditions. We concluded that rod-type helical coiled polymer PPI block performs crucial roles as intrinsically vapour-induced liquid crystallinity and self-reassembling property in the architecture of PTh- b -PPI.