Synthesis and Properties of Liquid Crystalline Polyacetylenes with Different Spacer Lengths and Bridge Orientations

Abstract

A group of mesomorphic polyacetylenes with different lengths of alkyl spacer −{HCC[(CH 2 ) m −OCO−Biph−OC7H15]} n − [1(m), m = 2, 3, 4, 9] and orientations of ester bridge −{HCC[(CH2)3−CO 2 −Biph−OC7H15]} n − [2(3)] are synthesized, and the effects of the structural variables on the properties of the polymers are investigated. The liquid crystalline acetylene monomers n-{[(4‘-heptoxy-4-biphenylyl)oxy]carbonyl}-1-alkynes 3(m) and 5-{[(4‘-heptoxy-4-biphenylyl)carbonyl]oxy}-1-pentyne 4(3) are prepared by consecutive etherification and esterification reactions. The T m and T i values of 3(m) decrease with an increase in the spacer length (m). While 3(3) shows a monotropic SmA phase, its counterpart with a different ester orientation 4(3) exhibits an enantiotropic SmB phase. The monomers are polymerized by transition-metal halides and carbonyls, and the polymerizations catalyzed by WCl6−Ph4Sn under optimal conditions produce polymers with high molecular weights (up to 1.2 × 105) in high yields (up to 92%). The structures and properties of the polymers are characterized and evaluated by IR, UV, TGA, DSC, POM, and XRD analyses. With the increase in the spacer length, the thermal stability of the polymers increases, their T g and T i decrease, and the packing arrangements in their mesophases change from mixed mono- and bilayer structures to a homogeneous monolayer structure. Compared to 1(3), 2(3) shows a blue-shifted absorption spectrum (Δλ max >30 nm), a higher T g and T i (ΔT ∼40 °C), and a better packed SmAd structure.

Liquid Crystalline and Light Emitting Polyacetylenes: Synthesis and Properties of Biphenyl-Containing Poly(1-alkynes) with Different Functional Bridges and Spacer Lengths

“…The polymer samples for the XRD measurements were prepared by freezing the molecular arrangements in the liquid crystalline states by liquid nitrogen as previously reported. [6][7][8] Monomer Synthesis. The alkyne monomer 3(3) was synthesized by etherization of 4′,4-biphenol with 5-chloro-1-pentyne followed by esterification of the resulting alcohol with lauric acid in the presence of DCC, TsOH, and DMAP (cf., Scheme 1).…”

“…7 In our previous work, we studied the mesomorphic properties of a pair of polyacetylenes with different bridge orientations and spacer lengths and revealed that the structural variables affected the mesomorphism of the polymers to a considerable extent. 8 To collect more information and to gain further insights into how structural variations affect mesomorphic properties of liquid crystalline polyacetylenes, in this study, we investigated the effects of functional bridge and spacer length on the mesomorphism of another pair of polyacetylenes, that is, poly- (5-{[(4′-{[(undecyl)carbonyl]oxy})-4-biphenylyl]oxy}-1-pentyne) [1(3)] and poly [m-({[(4′-{[(undecyl) Liquid crystals and light emitters are complementary in property; a polymer with the two electrooptical features (both liquid crystalline and light emitting) is of practical value, which may offer an array of exciting opportunities for high-tech innovations. Such a polymer, for example, may emit polarized light when aligned, which may be utilized for the construction of lighting and orientating layers in liquid crystal optical display devices, thus obviating the use of backlight lamps, polyimide films, and polarizing sheets.…”

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.…”

Synthesis, helicity, thermal stability, and low infrared emissivity of optically active polyacetylenes carrying tyrosine pendants

“…As a result, it can induce the polymer chain to spiral in a helical conformation. [19][20][21] Moreover, a variety of polyacetylenes containing mesogenic and chromophoric groups with ester, [22,23] ether, [24][25][26][27] amine, [28][29][30] thio, [31,32] and cyano [33,34] functionalities have been successfully synthesized and potentially used as liquid crystals, mesomorphic luminescent and conductive materials, and so on. Natural amino acids have been generally applied in the preparation of optically active materials as one of the most significant chiral resources.…”

“…[22][23][24][25][26][27][28][29][30][31][32][33][34] However, we had an interest in directly connecting chiral amino acid pendants to the polyacetylene backbone, and in this study, we made our best efforts to polymerize monosubstituted propiolamides (HC≡CCONHR), in which the triple bond was directly attaching to the carbonyloxy group. We used propiolic acid and tyrosine methyl esters in the synthesis of the monomer containing tyrosine derivatives as a functional group.…”