Cholesteric Liquid-Crystalline Elastomers Prepared from Ionic Bis–Olefinic Crosslinking Units

Abstract

ABSTRACT:A series of cyclosiloxane-based cholesteric LCEs were synthesized by using a LC monomer cholest-5-en-3-ol(3)-4-(2-propenyloxy)benzoate and an ionic divinyl monomer 2,2 0 -(1,2-ethenediyl)-bis [5-[(4-undecenoyloxy)phenyl]-azo]-benzenesulfonic acid. The polymers were prepared in a one-step reaction with ionic crosslinking contents ranging between mass content 0 and 11.8%. Their chemical structures and liquid-crystalline properties were characterized by FT IR, 1 H NMR, DSC, POM and X-ray measurement. The effective crosslink density (M c ) was determined by swelling experiments in mixed buffer/organic solvent mixtures, using Brannon-Peppas models. All the polymers exhibit thermotropic LC properties and reveal cholesteric phase. With increase of ionic crosslinking component in the polymers, the melting behavior disappears and the temperature of clear point decreases. Reflection spectra of cholesteric mesophase of the series of polymers showed that the reflected wavelength becomes broad and shifts to long wavelength with increase of the ionic crosslinking component in the polymer systems. [DOI 10.1295/polymj.37.277] KEY WORDS Liquid-Crystalline Elastomer / Sulfonate Groups / Cholesteric Phase / Polysiloxane / Slightly crosslinked liquid crystalline (LC) polymers that combine the properties of liquid crystalline phases and the elastic properties and form stability of polymeric networks are known as liquid crystalline elastomers (LCEs). They possess unique features originating from rubber elasticity, and the orientation of the mesogens can be controlled by mechanical forces as well as by electric and magnetic fields. As a result of these remarkable characteristics LCEs are promising materials for optoelectrical applications, including polarization halography, optical memory, integrated optical circuitry, and nonlinear optical generators.

Mesomorphic behavior and optical properties of liquid‐crystalline polysiloxanes bearing different chiral groups

“…For nematic and cholesteric structure of polymer systems, no strong peak appeared in the SAXS curves. However, a broad peak at 2θ ≈ 20° and 2θ ≈ 17° was observed in the WAXD curves of nematic and cholesteric polymers, respectively 28, 29. Therefore, it is a very important characteristic for judging cholesteric structure that broad diffraction angles appear at lesser angles than those of nematic structures in WAXD.…”

“…However, a broad peak at 2y % 20 and 2y % 17 was observed in the WAXD curves of nematic and cholesteric polymers, respectively. 28,29 Therefore, it is a very important characteristic for judging cholesteric structure that broad diffraction angles appear at lesser angles than those of nematic structures in WAXD. It suggests that the average distance between two neighbor LC molecules within the layers of the mesophase become broad due to the helix structure of cholesteric LC polymers.…”

Nanopillar Templating Augments the Stiffness and Strength in Biopolymer Films

“…Ionic cross-linkers may act to destabilize aligned mesophases. 55 To evaluate if an ionic cross-linked system would demonstrate the templated effect, we applied the technique to a purely ionic cross-linking system of chitosan and tripolyphosphate (TPP). We did not observe an increase in mechanical performance with the application of nanopillar topography (Table S8).…”

Cholesteric Liquid-Crystalline Thermosets Derived from Side-Chain Liquid-Crystalline Epoxy Oligomers

“…LC networks with cholesteric structures (Ch-LCNs) have attracted considerable interest due to their outstanding optical properties, in particular the selective reflection of circular polarized light and the angular dependence of the reflection wavelength [7]. In the past decade, research into Ch-LCNs have expanded rapidly due to their unique properties and potential applications in numerous areas, especially in the fields of nonlinear optical materials and electro-optical materials [8][9][10][11]. According to the cross-link density, two classes of Ch-LCNs emerge: highly cross-linked cholesteric liquid crystalline thermosets (ChLCTs)1 and lightly cross-linked cholesteric liquid crystalline elastomers (ChLCEs).…”