High Hole Mobility for a Side‐Chain Liquid‐Crystalline Smectic Polysiloxane Exhibiting a Nanosegregated Structure with a Terthiophene Moiety

Abstract

Side-chain liquid-crystalline siloxane polymers bearing terthiophene moieties as mesogenic pendant groups have been synthesized. An alkenylterthiophene derivative was treated with poly(hydrogenmethylsiloxane) and poly(dimethylsiloxane-co-hydrogenmethylsiloxane)s in Me(2)SiO/MeHSiO ratios of 1:1 and 7:3, respectively, in the presence of the Karstedt catalyst, to produce pale yellow polymers. The degrees of introduction of the mesogenic unit were 100, 50, and 30%, respectively. The polymers exhibit ordered smectic phases at room temperature. The copolymers with dimethylsiloxane units form smectic phases as a consequence of nanosegregation between the mesogenic units and siloxane backbones with the alkylene spacers. Time-of-flight measurement reveals that the hole mobility exceeds 1×10(-2) cm(2) V(-1) s(-1) in the ordered smectic phase of the copolymer with a degree introduction of the mesogenic units of 50%. This value is comparable to that of the highly ordered mesophases of low-molecular-weight derivatives of phenylnaphthalene and terthiophene. Because of the segregation behavior induced by the flexible backbone, a closer molecular packing structure favorable for fast carrier transport may be formed in the smectic phase of the copolymer in spite of the low density of the mesogenic groups.

Progress in side-chain thiophene-containing polymers: synthesis, properties and applications

“…Alternatively, postfunctionalizing nonconjugated prepolymers with electroactive unites as pendant side chains is a promising strategy to precisely synthesize such electroactive polymer materials for a number of organic electronic applications. Particularly, approaches to post-functionalize flexible polymer backbones with thiophene-based units include weak interaction (e.g., hydrogen bonds [63] and ionic interactions [64]) and covalent bond [26,[65][66][67][68].…”

Design of liquid-crystalline electronic functional materials through nanosegregation

“…The introduction degrees of the terthiophene side-chains were 100 %, 50 %, and 30 % for 2a, 2b, and 2c, respectively (Figure 3(a)). 24 These LC polymers exhibit a smectic E (SmE) phase at room temperature and do not crystallize even when they are cooled to -50 ºC. An observation of the optical textures of polymer 2b using a polarizing optical microscope reveals the formation of domain structures whose sizes are several hundred μm (Figure 3(b)).…”

Functional liquid-crystalline polymers and supramolecular liquid crystals

“…For example, functional main-chain LC polymers 5 have been prepared to exhibit electron conductivities and luminescence properties. 11,12 Photofunctional, 13,14 electro-active, [15][16][17][18] and ion-active [19][20][21][22][23][24] groups have been incorporated into the side chains of LC polymers. For example, LC polymers 6 and 7 bearing electroactive moieties are obtained by using π-conjugated molecules as mesogenic units.…”

“…For example, LC polymers 6 and 7 bearing electroactive moieties are obtained by using π-conjugated molecules as mesogenic units. [15][16][17][18] The introduction of azobenzene moieties into the side chain of LC polymers leads to the development of photoresponsive optical systems 8 and photo-actuators. 25,26 Anisotropic two-dimensional (2D) ion-conductive materials 9 and 10 are achieved by incorporation of ionic moieties or oligo(oxyethylene) units complexed with inorganic salts in the spacer or the terminal group of the side-chain LC polymers.…”