Synthesis and Properties of Polyacetylenes Containing Terphenyl Pendent Group with Different Spacers

Abstract

Liquid-crystalline, monosubstituted acetylenes containing terphenyl pendent group with varying spacer lengths [HCC(CH2) n O-terphenyl-CN, AnCN, n = 1, 6] and its polymers PAnCN were synthesized. Also, the effects of the structural variation on their properties, especially their mesomorphism, UV and photoluminescence behaviors, were studied. The monomers are prepared by simple Suzuki coupling reactions. High yields and high trans-content of polyacetylenes were obtained by polymerization using [Rh(nbd)Cl]2 catalyst. The polymer with long spacers (hexamethylene), that is, PA6CN, formed a nematic mesophase when heated and cooled, however the polymer with short spacers (methylene), that is, PA1CN, could not exhibit liquid crystallinity at elevated temperatures. Upon photoexcitation by keep the constant photons of excitation, PA1CN emits ultraviolet emission (λmax ∼ 311 nm) but PA6CN gives a stronger emission (λmax∼308 nm), indicating that the emission intensity increases with the spacer length due to orientation of main chain by alignment of mesogenic pendant. Short spacer between polyacetylene and mesogens hindered alignment of the main chain, consequently lower fluorescence emission, and loss mesophase of the polymer was induced by short spacer due to disturbance of rigid main chain.

Preparation of a solution‐processable, nanostructured ionic polyacetylene

“…The position of the modes indicates the dodecyl chains are well‐ordered in the solid state, adopting predominately an all‐ trans conformation. The propargyl modes are observed at 3194 cm −1 (ν(CCH) stretch), 2123 cm −1 (ν(CC) stretch), 970, 948 (ν(CCH) wag), and 680 cm −1 (ν(CCH) bend) …”

Synthesis and liquid crystalline behavior of 2,5-disubstituted styrene-based random copolymers: Effect of difference in length of the rigid core on the mesomorphic behavior of mesogen-jacketed liquid crystalline polymers

“…According to SelfCompacting Chain Model, the entropy gain of the side groups obtained from liquidemesophase transition of the copolymer would be less than that of the homopolymer, resulting in a less tendency for a copolymer to form a mesomorphic state [35,36,40]. 4.85 P 9 5.09 P 12 5.56 Fig. 13.…”

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.…”