Synthesis of optically active poly(N-propargylsulfamides) with helical conformation

Fluorescence-Selective Absorption and Circularly Polarized Fluorescence Energy Transfer Assist the Generation of Multicolor Circularly Polarized Luminescence in Chiral Helical Polyacetylene-Based Janus Nanofibers

Chiroptical nanomaterials with circularly polarized luminescence (CPL) performance have aroused increasing attention. Herein, multicolor CPL-active Janus nanofibers are prepared through a simple parallel electrospinning method using chiral helical polyacetylenes as the chiral source and achiral fluorophores as the fluorescent source. Interestingly, despite a direct spatial isolation between the chiral component and the fluorescent component, blue and green CPL emissions can still be obtained due to the fluorescence-selective absorption behavior of chiral helical polyacetylenes, with a satisfactory dissymmetric factor (glum) of 2 × 10-2 and 2.5 × 10-3, respectively. Moreover, by taking advantage of the circular polarization fluorescence energy transfer process, red CPL emission is further achieved using the obtained blue and green CPL as energy donors and the achiral red fluorophore as an energy acceptor. The present work offers a facile approach to prepare multilevel-structured chiroptical materials with promising application potentials in a flexible photoelectric device.

Synergism between LDLB and true CD to achieve angle-dependent chiroptical inversion and switchable polarized luminescence emission in nonreciprocal nanofibrous films

Chiroptical nanomaterials including chiralized advanced functional nanofibers have attracted ever-increasing interest in multi-disciplinary fields. Nowadays, electronic circular dichroism (CD) is the most widely used technique to evaluate chiral properties. Numerous studies have shown that the occurrence of linear dichroism and linear birefringence (LDLB) phenomenon in chiral micro-/nano-architectures makes it challenging to distinguish their inherent chiral information. However, tactfully combining LDLB with true circular dichroism (true CD) may lead to a new class of chiroptical materials. In this study, we demonstrate that transparent nanofibrous films infiltrated with poor solvents can show unique LDLB properties, which allows achiral nanofibrous films to exhibit these features regularly opposite Cotton signals by simply flipping the two faces of the same film or even rotating the testing angles of the sample around its optical axis in a single face. More importantly, we can quantitatively distinguish the contribution of LDLB from true CD in the chiral composite nanofibrous system and even effectively combine them into a single unity. This kind of adjustable flexible film material shows outstanding value in the field of optoelectronics. Its large intrinsic LDLB feature and angle-dependent, non-reciprocal transmission for polarized lights are exploited to fabricate programmable polarized light-emitting devices through the resin encapsulation process. This study may provide an easy and powerful way for the construction and implementation of novel polarization optical materials towards future intelligent optical encryption and advanced anti-counterfeiting devices.

Organocatalytic chiral polymeric nanoparticles for asymmetric aldol reaction

Chiral polymeric particles (CPPs) were studied extensively in recent years due to their importance in pharmaceutical applications. Here, nanosized CPPs were synthesized and applied as catalysts for direct asymmetric aldol reaction. The CPPs were prepared by miniemulsion or inverse miniemulsion based on various chiral amino acid derivatives and characterized by dynamic light scattering and scanning electron microscopy. The nanoparticles with spherical structure between 250 and 400 nm and high chiral surface area were used as catalysts in the aldol reaction at room temperature without additional solvent. l-tryptophan gave the highest enantiomeric excess, >86% with similar catalytic performance four times.

Chiral Helical Polymer/Perovskite Hybrid Nanofibers with Intense Circularly Polarized Luminescence

Chiral perovskites with circularly polarized luminescence (CPL) performance have attracted tremendous attention. This contribution reports a convenient and universal strategy for constructing chiral helical polymer/perovskite hybrid nanofibers with outstanding CPL properties. The hybrid nanofibers are prepared through a one-step electrospinning method in which chiral helical polyacetylenes, perovskite nanocrystals, and polyacrylonitrile serve as a handed-selective fluorescence filter, fluorescent source, and electrospinning matrix, respectively. Specially, perovskite nanocrystals are in situ formed during the electrospinning process, which avoids the tedious process for preparing and purifying perovskites. The prepared hybrid nanofibers all exhibit good long-time stability in air, owing to the effective protection effect of polymer matrix. More importantly, intense CPL emissions with high dissymmetry factor up to 10^-2 level are obtained in the hybrid nanofibers. Furthermore, the emission color of CPL can be easily tuned by adjusting the precursors of perovskites. This work provides an efficient technique toward various kinds of CPL-active perovskite nanomaterials for both scientific research and future practical applications.

Helically twining polymerization for constructing polymeric double helices

Double helical substituted polyacetylenes (DHSPs) were successfully prepared by a novel chiral induction–helically twining polymerization strategy.

Optically active helical polyacetylene/Fe3O4 composite microspheres: prepared by precipitation polymerization and used for enantioselective crystallization

The precipitation polymerization for constructing chiral, magnetic microspheres based on substituted polyacetylene and Fe₃O₄ nanoparticles: preparation and application in enantioselective crystallization.

Preparation and application of abietic acid-derived optically active helical polymers and their chiral hydrogels

A novel chiral monomer N-propargyl abietamide, M1, was synthesized from abietic acid and catalytically polymerized with (nbd)Rh+B-(C6H5)4 (nbd=norbornadiene), providing polymer [poly(1)] with a molecular weight of 13,000-36,000 at a yield of 59-84%. Poly(1) did not form stable helices in tetrahydrofuran at room temperature whereas copolymerization of M1 and the achiral N-propargylamide monomer, M2, led to the formation of helical optically active copolymers as indicated by circular dichroism studies, UV-vis spectroscopy, and specific optical rotation measurements. Hydrogels were prepared based on an optically active helical copolymer, poly(M1(0.32)-co-M2(0.68)) that exhibited enantioselective recognition toward l-alanine. The novel chiral polymers derived from abietic acid are expected to find applications in such areas as chiral recognition, chiral resolution, and chiral catalysis.