Versatile and facile preparation of chiral polyacetylene-based gel film and organic-inorganic composites

A new SiH-containing chiral polyacetylene, poly[p-[{(S)-2-methylbutyl}methylsilyl]-phenylacetylene] (1), with a moderate molecular weight (M_w 4.4 × 10⁴; M_w/M _n 2.4) was obtained with [RhCl(nbd)]₂-NEt₃ catalyst. IR and ¹H NMR studies revealed that the SiH group in 1 remains intact, with no side reactions such as hydrosilylation and hydrolysis. Furthermore, 1 readily turned into a transparent gel film with Si-O-Si linkages simply by standing in air at room temperature. The polymer 1 exhibited a quite large optical rotation ([α]_D = 600°, c = 0.12 g/dL in toluene at 25 °C), corresponding to large molar ellipticities ([θ]_ext = -5.1 × 10³ deg·cm ²·dmol^-1 at 326 nm and 4.7 × 10³ deg·cm²·dmol^-1 at 371 nm). The CD intensity of the gel film scarcely changed in the range from 25 to 85 °C, presumably due to Si-O-Si cross-linking. Moreover, organic-inorganic composite materials were easily obtained by stirring inorganic particles such as titania and silica gel in the polymer solution. The prepared composites were characterized by AFM, EDX, and SEM.