Advances in liquid crystalline conjugated polymers

Abstract

ABSTRACT:We review advances in liquid crystalline (LC) conjugated polymers by focusing on (i) ferroelectric and (ii) photoresponsive LC conjugated polymers. In Part 1, LC polyphenylene derivatives were synthesized through substitution of fluorine-containing chiral LC groups into side chains. Poly (para-phenylene) [P1] and poly (meta-phenylene) [P2] derivatives showed chiral smectic C phases responsible for ferroelectricity. They exhibited quick response to electric field, giving switching times of \1 s between two bistable states. The spontaneous polarization (P S ) of P2 remained unchanged even after the electric field became zero, affording the residual polarization (P R ) whose value was the same as that of P S . This indicates that P2 has a potential memory function based on FLC nature. In Part 2, poly (para-phenylenevinylene)[P5] and poly(bithienylene-phenylene) [P6] derivatives were synthesized by introducing dithienylethene moieties into side chains. Drastic quenching of fluorescence occurred when the photoresponsive moiety changed from an open form to a closed one upon an irradiation of ultraviolet light. The quenched fluorescence was recovered through a photoisomerization from the closed form to the open one. Macroscopically aligned P6 film exhibited a linearly polarized fluorescence with significant anisotropy. Reversible quenching and emitting behavior in anisotropic fluorescence was controlled by the photochemical switching.

Formation of perfluorinated polyphenylenes by multiple pentafluorophenylation using C6F5Si(CH3)3

“…against decafluorobiphenyl (1a) provided pentafluorophenyl derivative 2a as the main product, accompanied by nonafluorobiphenyl derivative 3a via successive pentafluorophenylation against the para-position of 2a (Table 1, Entry 1). Furthermore, multiple attack of C 6 F 5 Si(CH 3 ) 3 against the terminal positions occurred for 3a to provide tridecafluoroterphenyl derivative 4a (Table 1, Entries 2 and 3). Although these perfluorinated oligo(phenylene)s 2a-4a have been reported previously [6,14], detailed assignments of 19 F NMR peaks have not been established.…”

“…We assigned the 19 F NMR peaks of linear perfluoroaryl compound 2a-4a using a 19 F-19 F homodecoupling method and employed the assignments of our previous study [18]. In similar fashion to 1a, octafluorotoluene (1b) provided linear perfluoroaryl derivatives 2b, 3b, and 4b by the terminal position attack of C 6 F 5 Si(CH 3 ) 3 (Table 1, Entries 4 and 5). In the 19 F NMR spectra, although CF 3 groups of the linear perfluoroaryl compound 2a-4a appeared as triplet peaks coupled with the ortho-fluorines, a weak doublet CF 3 peak appeared in the [ ( S c h e m e _ 1 ) T D $ F I G ] Scheme 1.…”

“…In our pentafluorophenylation method using C 6 F 5 Si(CH 3 ) 3 described herein, a straightforward reaction procedure was used which differed from the previously reported unstable organometallics, C 6 F 5 Li and C 6 F 5 MgBr. The pentafluorophenylation with C 6 F 5 Si(CH 3 ) 3 was performed in a Teflon 1 vessel at ambient temperature without an inert atmosphere.…”

“…reaction of the latter compound with (C 6 F 5 )Si(CH 3 ) 3 , multiple pentafluorophenylation at the para-positions occurred to provide nonafluorobiphenylyl derivatives, the structures of which were determined by NMR and DFT analyses. In the present study, we target several perfluoroarenes as possible precursors of perfluoro(polyphenylene)s and furthermore investigate a substituent effect in the aromatic ring for the multiple pentafluorophenylation of (C 6 F 5 )Si(CH 3 ) 3 , mainly using NMR and the MALDI-TOF-MS techniques.…”

A new class of nanostructured supramolecular organic semiconductors based on intertwined multi-lamellar co-assemblies in π-conjugated liquid-crystalline side-chain polymers

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] The first class of materials takes advantage of the block copolymer's ability for phase separation into well-ordered morphologies (spherical, cylindrical or lamellar) to form separate conduction pathways for charge carriers, thanks to the antagonistic chemical nature of each block at the origin of the nanosegregation. [24][25][26][27] However, the optimal charge transport properties also require the formation of long-range correlated structures with an orientational control of regular pathway alternation.…”