Chiral Photonic Liquid Crystalline Polyethers with Widely Tunable Helical Superstructures

Abstract

Liquid crystalline polymers with tunable structures on the scale of visible wavelength are important in optical technology due to their enhanced mechanical stability, processability, and structural integrity. Herein, we report a series of cholesteric liquid crystalline (CLC) polyethers with a widely tunable pitch length and a broad CLC phase window through a bottom-up structural design. The well-defined multicomponent polyethers were successfully synthesized by utilizing monomer-activated anionic ring-opening polymerization. Through adjustment of the composition of chiral cholesteryl (Ch) and photochromic azobenzene (Az) mesogenic moieties, rich phase behaviors have been discovered, and a phase boundary diagram was constructed consequently, wherein cholesteric helical superstructures in a broad composition range and temperature window straight down to the glassy state at room temperature were achieved. Particularly, the planar oriented helical superstructures can exhibit widely tunable and switchable reflections over the entire visible range across red, green, and blue colors through temperature and light control, which are closely related to the extraordinary flexibility of the polyether backbone. Their thermo-light dualresponsive properties provide an alternative opportunity to fabricate smart and switchable polymeric LC materials for optical applications.

Quasi-Living Copolymerization of Aryl Isocyanates and Epoxides

“…In this work, we adopted the approach of Lewis pair polymerization, which has demonstrated great potential to fine-tune the polymerization process with regard to reaction conditions and livingness, as well as chemo- or regioselectivity. − A weak Lewis base of onium salt (e.g., NOct 4 Br) as a nucleophilic anion initiator was particularly introduced in order to afford anionic copolymerization, in which a large-sized cation is expected to shield the growing anionic species and thus minimize the chain backbiting and the formation of oxazolidinones. Lewis acid of i -Bu 3 Al is combined to foster the ring-opening of epoxides on the one hand; − on the other hand, its successive coordination with the propagating chain end and the incoming monomer could potentially mediate alternating copolymerization of isocyanates and epoxides, which is further supported by the DFT calculations.…”

Cholesteric Liquid Crystalline Polyether with Broad Tunable Circularly Polarized Luminescence

“…The monomers of Ch and CB were prepared according to the procedure reported previously. The Ch and CB homopolymers were synthesized via anionic ring-opening polymerization by following the methods described previously. ,− …”

“…In order to tailor CPL behaviors, various CLC materials containing different chiral motifs have been designed. − Among them, polymeric CLC materials have drawn particular attention due to their good processability, mechanical stability, structural integrity, and capability to incorporate diverse functionalities. To fabricate CLC polymers, the introduction of chiral mesogens to form side-chain LC polymers (LCPs) is a common approach. ,,− However, loss of chiral superstructures is generally observed, and an achiral smectic LC polymer is usually obtained. Recently, we have reported a CLC polyether with tunable and switchable reflections by copolymerization of chiral mesogens and photoresponsive groups, where the flexible polyether backbone was found to play a crucial role to facilitate the twisting of the chiral mesogens and alleviate the steric hindrance imposed by the backbone, and ordered helical packing in the LCP with high tunability can be eventually achieved.…”

Supramolecular Chirality in Azobenzene-Containing Polymer System: Traditional Postpolymerization Self-Assembly Versus In Situ Supramolecular Self-Assembly Strategy

“…The results demonstrated the presence of supramolecular interactions between the neighboring side-chain Azo chromophores along the polymer backbone, which is similar to the previous results from Angiolini and coworkers. Taken together, many excellent works have been published for chiral Azo-polymers in the solid film [183][184][185][186][187][188], which further enhance our understanding of supramolecular chirality and offer many opportunities to develop new functional materials.…”