Thermotropic behavior of side-chain liquid-crystalline copolymers from maleic anhydride and mesogen-containing methacrylates

Abstract

SUMMARY: Side-chain liquid-crystalline copolymers (SCLCPs) were synthesized by copolymerization of maleic anhydride (MA) and mesogenic methacrylates. For copolymers with a hexyl spacer and methoxybiphenyl mesogens, smectic A1 and smectic E1 mesophases are observed. Furthermore, it has been found that the isotropization temperature increases and the width of the monotropic smectic A1 mesophase decreases with increasing MA content. For methoxybiphenyl-containing copolymers with about 25 mol-% MA, the glass transition temperature decreases with increasing spacer length, whereas the isotropization temperature shows little dependence on spacer length, although a small odd-even effect is observed. For octyl or shorter spacers, these polymers exhibit a smectic E mesophase, whereas for longer spacers smectic B mesophases were observed. These mesophases are succeeded by a smectic A1 mesophase for SCLCPs with heptyl or longer spacers. SCLCPs with cyanoazobenzene mesogens exhibit only a smectic Ad mesophase, whereas SCLCPs with cyanobiphenyl mesogens are not liquid crystalline.

Liquid Crystallinity and Other Properties in Complexes of Cationic Azo-Containing Surfactomesogens with Poly(styrenesulfonate)

“…It is noteworthy that Crivello et al observed a weak first-order and sharp second-order peak for an NC−O azo mesogen covalently bound by an alkyl spacer ( n = 4, 6, 8, 10) to a poly(α-methylstyrene) backbone . The extinction or reduction in intensity of the first-order peak is regularly reported in the literature (see, for example, refs , , and − ) and is generally attributed to an additional plane of electron density within the layers . The appearance of LC order in O 2 N−N(Me)10Q/PSS and NC−O10Q/PSS supports the attribution of the weak peaks observed in their DSC thermograms to the clearing temperature of a poorly developed LC phase.…”

Enhancing Long-Range Ordering of P3HT by Incorporating Thermotropic Biphenyl Mesogens via ATRP

“…Flexible side chains attached to the conjugated backbone support facile deposition, improve flexibility, and increase the mobilities. Methoxy biphenyl (MeOBP) was selected as the mesogen for this study due to its thermotropic behavior with high thermal stability and lamellae forming behavior. − In previous studies of homopolymers and copolymers of MeOBP, lamellar stacking has been observed in both crystalline and smectic phases. The ability of the biphenyl moiety to undergo π stacking in the crystalline and smectic phases enables the formation of well-defined microdomains .…”

Photoresponding ionic complex containing azobenzene chromophore for use in birefringent film

“…In addition, the first-order reflection peak is very weak and the second-order reflection peak is the most intense. This might be related to interference effects of an additional plane of symmetry in their lamellar electron density profile [22][23][24].…”