Homochiral Evolution in Self-Assembled Chiral Polymers and Block Copolymers

Phase Separation Pathways of Chiral Macromolecules at Liquid-Liquid Interfaces

The phase behavior of chiral macromolecules is one of the key subjects in chemistry, biology, and materials science. Here we take poly(L-lactic acid) (PLLA) and mesomeric poly(D, L-lactic acid) (mPLA) mixtures as a model system and investigate the phase separation behaviors in double emulsion droplets. At high mPLA compositions, phase separation creates transient bicontinuous networks or discrete domains at the liquid-liquid interface and eventually generates eyeball-like microcapsules. At low mPLA compositions, phase separation occurs first but is trapped by the lateral crystallization of PLLA, leading to spindle-like microcapsules. The dynamic pathways of phase separation can be further modulated by PLA-based amphiphilic block copolymers, so that microcapsules are configurable between the eyeball-, spindle-, and Janus-like structures. By comparing with phase separation on a plane substrate, we unveil that the phase separation dynamics at the double emulsion interfaces are significantly affected by interfacial properties and hydrodynamic effects. This work clarifies the phase transition dynamics of PLLA/mPLA mixtures at liquid-liquid interfaces and sheds insight into the phase behaviors of chiral macromolecules for their structural modulation.

Chiral Communication between Enantiomeric Sergeants and Achiral Soldiers in Racemic Triblock Copolymers with Heterochiral Cores for Triggering Multiple Helicity Inversions

Amplification of asymmetry in complex supramolecular/polymer system results from the delicate interplay of chiral and achiral structures. Here, a novel approach to the racemic sergeants and soldiers (S&S) effect, using enantiomeric sergeants (Sgt.) and achiral soldiers (Sold.), achieves unique precise control over both intensity and sign of global chirality. Chiroptical assemblies of different dimensions in racemic S&S copolymers can be constructed in situ via polymerization-induced chiral self-assembly (PICSA). We systemically investigated chiral communication pathways between chiral-chiral, chiral-achiral, and two oppositely configured azobenzene (Azo) segments, which robustly affect the global chiroptical activity of the racemic S&S assemblies. Chain length-, Sgt./Sold. ratios-, and temperature-dependent CD/UV/Vis, small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results provided insights into the kinetics for chiroptical inversions. LC phase transitions, the helical preferences of the Sgt. and Sold. units, and the stability of the "chiral core" allow racemic S&S copolymer assemblies to exhibit chiral conflict between heterochiral blocks in an enantioselective fashion.

Real-Time Observation of Ultrafast Concerted Dynamics between Energy and Chirality Transfer by Femtosecond Time-Resolved Circular Polarization Luminescence Spectroscopy

Elucidating the underlying mechanism of effective chirality and energy transfer processes observed in biological assemblies has cross-disciplinary significance, and it is of special interest in the fields of chemistry and biology due to the pivotal role of chirality in life. Challenges in the field include how to achieve real-time monitoring of the chirality and energy transfer dynamics simultaneously, as well as how to distinguish whether these processes take place in the ground or excited state. Herein, we achieve the first attempt at real-time observation of the concerted ultrafast dynamics between the Förster resonance energy transfer (FRET) and the generation of circularly polarized luminescence (CPL) in the excited state in near-infrared CPL supramolecular nanofibers (SNFs) by using femtosecond time-resolved circularly polarized luminescence (fs-TRCPL) spectroscopy. Our findings reveal a cooperative interplay between FRET and CPL emission, unfolding over time scales from several to hundreds of picoseconds. Notably, we identify that the pivotal mechanism leading to a 0.045 glum value in SNFs is the difference in the FRET rates between left- and right-handed circularly polarized emission channels, which is a reason beyond the well-known relationship of the electronic and magnetic dipoles. Our results not only shed light on the understanding of the chirality transfer mechanism in the excited states but also pave the road for the development of novel CPL materials in the future.

Dynamic Covalent Bonds-Mediated Color-Switchable Circularly Polarized Luminescence in Helical Assemblies of Achiral Liquid Crystal Block Copolymer Films

Circularly polarized luminescence (CPL) film attracted considerable attention in information storage and encryption, three-dimensional display, and chiral recognition. However, due to the limited molecular mobility within thin film, achieving a high asymmetry factor and non-contact modulation of CPL remain challenging. In this work, color-switchable homochiral CPL films with high luminescence asymmetry factor (glum~0.11) were constructed based on the co-assembly of a liquid crystal block copolymer (poly (ethylene oxide)-b-poly (methyl methacrylate) bearing cyanostilbene group) with axial chiral dinaphthalene diamine derivatives (R/S-DINBPA). Mechanistic investigation revealed that the efficient stacking of R/S-DINBPA with cyanostilbene groups and the liquid crystal field provide the driving force for chiral transfer and amplification. The dynamic covalent bonds of the cyanostilbene groups endow the film with chiral fixation ability and enable precise modulation of CPL luminescence bands under UV light irradiation, making it suitable for chiral patterned anti-counterfeit encryption. This facile strategy provides a general platform for designing intelligent chiroptical materials.

Photo-Induced Radical Generation of Supramolecular Gel with Sign-Inverted and White-Light Circularly Polarized Luminescence

The realization of persistent luminescence and in particular circularly polarized luminescence (CPL) of organic radicals remains a challenge due to their sensitivity to oxygen at ambient conditions and elusive excited state chirality control. Here, it is reported that UV-irradiation on a supramolecular gel from a chiral triarylamine derivative, TPA-Ala, led to the formation of luminescent radicals with bright CPL. TPA-Ala can form an organogel in chloroform with blue emission and supramolecular chirality as demonstrated by both CD and CPL signals. Upon UV 365 nm irradiation, an emission color change from blue to cyan is observed due to the formation of photo-induced radicals. Interestingly, it is found that the supramolecular gel radicals showed stable luminescence with a lifetime ≈ 10 days in dark environments and inverted CPL, which represents a scarce example with persistent CPL from doublet-state due to oxygen isolation ability of the gel network. Furthermore, doping a guest dye, Rhodamine B (RhB), into the supramolecular gel (RhB/TPA-Ala = 30% in molar ratio) successfully obtained a transient white-light CPL through the superposition of photo-induced radical and guest dye emissions. This work provides a useful methodology for the fabrication of radical-based CPL materials via a supramolecular assembly approach.

Odd-even effect in chiral side-chain cyanobiphenyl block copolymer assemblies prepared by polymerization-induced chiral self-assembly

The precise control of the chirality of polymer assemblies is a challenge faced by scientists and has received significant attention in recent years. In this study, we employed the polymerization-induced chiral self-assembly (PICSA) method to create chiral side-chain cyanobiphenyl (CB) block copolymer (BCP) assemblies. The flexible spacers in chiral CB monomers were regulated to exhibit two distinct odd-even effects in the supramolecular asymmetrical arrangement of the CB mesogens inside BCP assemblies. The research results indicated that the liquid crystalline properties of CB mesogens significantly influence the magnitude and sign of their chiroptical properties. These findings have significant implications for the design of polymer assemblies with designable chiroptical functions.

Homochiral π-Rich Covalent Organic Frameworks Enabled Chirality Imprinting in Conjugated Polymers: Confined Polymerization and Chiral Memory from Scratch

Optically active π-conjugated polymers (OACPs) have garnered increasing research interest for their resemblance to biological helices and intriguing chirality-related functions. Traditional methods for synthesizing involve decorating achiral conjugated polymer architectures with enantiopure side substituents through complex organic synthesis. Here, we report a new approach: the templated synthesis of unsubstituted OACPs via supramolecularly confined polymerizations of achiral monomers within nanopores of 2D or 3D chiral covalent organic frameworks (CCOFs). We show that the chiral π-rich nanospaces facilitate the in situ enantiospecific polymerization and self-propagation, akin to nonenzymatic polymerase chain reaction (PCR) system, resulting in chiral imprinting. The stacked polymer chains are kinetically inert enough to memorize the chiral information after liberating from CCOFs, and even after treatment at temperature up to 200 °C. The isolated OACPs demonstrate robust enantiodiscrimination, achieving up to 85 % ee in separating racemic amino acids. This underscores the potential of utilizing CCOFs as templates for supramolecularly imprinting optical activity into CPs, paving the way for synthetic evolution and advanced functional exploration of OACPs.

Cross-domain Chirality Transfer in Self-Assembly of Chiral Block Copolymers

Chirality transfer is essential to acquire helical hierarchical superstructures from the self-assembly of supramolecular materials. By taking advantage of chirality transfers at different length scales through intra-chain and inter-chain chiral interactions, helical phase (H*) can be formed from the self-assembly of chiral block copolymers (BCPs*). In this study, chiral triblock terpolymers, polystyrene-b-poly(ethylene oxide)-b-poly(L-lactide) (PS-PEO-PLLA), and polystyrene-b-poly(4-vinylpyridine)-b-poly(L-lactide) (PS-P4VP-PLLA) are synthesized for self-assembly. For PS-PEO-PLLA with an achiral PEO mid-block that is compatible with PLLA (chiral end-block), H* can be formed while the block length is below a critical value. By contrast, for the one with achiral P4VP mid-block that is incompatible with PLLA, the formation of H* phase would be suppressed regardless of the length of the mid-block, giving cylinder phase. Those results elucidate a new type of chirality transfer across the phase domain that is referred as cross-domain chirality transfer, providing complementary understanding of the chirality transfer at the interface of phase-separated domains.

Self-Assembled Homopolymeric Spherulites from Small Molecules in Solution

Polymeric spherulites are typically formed by melt crystallization: spherulitic growth in solution is rare and requires complex polymers and dilute solutions. Here, we report the mild and unique formation of luminescent spherulites at room temperature via the simple molecule benzene-1,4-dithiol (BDT). Specifically, BDT polymerized into oligomers (PBDT) via disulfide bonds and assembled into uniform supramolecular nanoparticles in aqueous buffer; these nanoparticles were then dissolved back into PBDT in a good solvent (i.e., dimethylformamide) and underwent chain elongation to form spherulites (rPBDT) in 10 min. The spherulite geometry was modulated by changing the PBDT concentration and reaction time. Due to the step-growth polymerization and reorganization of PBDT, these spherulites not only exhibited robust structure but also showed broad clusterization-triggered emission. The biocompatibility and efficient cellular uptake of the spherulites further underscore their value as traceable drug carriers. This system provides a new pathway for designing versatile superstructures with value for hierarchical assembly of small molecules into a complicated biological system.

Homohelical Self-Assembly of Trimer of α-Cyclodextrin and Octamolybdate

The ability to conceptually mimic biomolecules to construct emergency-functional homospiral aggregates remains a long-standing challenge. Herein, we report artificial homohelical assembly by blending inorganic polyoxometalates (POMs) and organic cyclodextrin molecules. The chiral double-helical chains have been achieved by a left-hand arrangement of trimer-trimer. The trimer is formed by three {Mo8}@α-CD inclusive complexes as a Whittaker-style paddle wheel. During the process of assembly, chiral transfer and amplification from molecule to superstructure were observed. The enantioselective adsorption of the homohelical aggregate toward (R/S)-1,1'-binaphthyl-2,2'-diamine was further demonstrated. The interaction of {Mo8} and α-CD in solution was investigated. This work opens a wide scope for the design of a homohelix, enriching POM-based inorganic-organic materials.

Helix-Induced Asymmetric Self-Assembly of π-Conjugated Block Copolymers: From Controlled Syntheses to Distinct Properties

Conspectusπ-Conjugated polymers have gained significant interest because of their potential applications in optoelectronics, bioelectronics, and other domains. The controlled synthesis of π-conjugated block polymers optimizes their performance and enables novel properties and functions. However, precise control of the self-assembled architectures of π-conjugated polymers remains a formidable challenge. Inspired by the precise helical architectures of biomacromolecules, the helical polymers and the supramolecular helical assemblies have gained significant attention. Helical polymers with an excess of one-handed helicity can be optically active with a strong tendency toward self-assembly. Incorporating a helical polymer into a π-conjugated polymer can induce asymmetric helical assemblies, leading to novel chiral materials with unique functionalities.To control the self-assembly of architectures, π-conjugated polymers are usually synthesized into block copolymers by incorporating a polymer with self-assembling characteristics. Although various π-conjugated block copolymers have been produced, precise and asymmetric self-assembly is still challenging and has rarely been addressed. Incorporating helical polymers into the π-conjugated polymers can induce a precise and asymmetric self-assembly, which transfers the chirality of the helical polymer block to the π-conjugated polymer, resulting in chiral supramolecular architectures with unique chiroptical properties and functionalities. However, synthesizing hybrid block copolymers containing two distinct polymer blocks is complicated. Some general strategies such as connecting the chain ends of two preformed homopolymers and extending the chain of a prefabricated π-conjugated polymer with a second monomer are time-consuming and require complex synthetic protocols. Therefore, developing novel strategies for the facile synthesis of π-conjugated block copolymers with a predictable molar mass, low dispersity, and tunable composition is of practical importance.Recently, we investigated a controlled synthesis of helical polyisocyanides, helical polyallenes, and helical polycarbenes by developing advanced Pd(II) and Ni(II) catalysts. These helical polymers were successfully incorporated into π-conjugated polymers, including polythiophene, polyfluorene, and poly(phenyleneethynylene), via a one-pot sequential living block polymerization of the two distinct monomers using Pd(II)- or Ni(II)-complexes as catalysts. As a result, a variety of well-defined π-conjugated block copolymers containing helical polymeric blocks were readily synthesized. Although the copolymerized monomers possess different structures and polymerization mechanisms, the one-pot block copolymerization followed a living polymerization mechanism and provided the desired π-conjugated block copolymers in high yields with controlled molar mass, narrow size distribution, and tunable composition.Remarkably, the helical polymeric block induces the π-conjugated block copolymer asymmetric self-assembly into a supramolecular, one-handed helical architecture resulting in distinct optical properties. More interestingly, by utilizing the crystallization of conjugated blocks and one-handed helical blocks, the crystallization-driven and helix-induced precise asymmetric living self-assembly yielded a family of uniform and single-handed helical architectures with controlled dimensions, narrow distribution, and well-defined helicity. The transfer of helical chirality to the supramolecular architectures rendered the achiral π-conjugated blocks with unique chiroptical properties such as the emission of white light over a broad optical spectrum and the circularly polarized luminescence.

Chiral Polymer Dots Show Unexpected Versatility of Highly Ordered Self-Assembly into Chiroptical Liquid Crystals, Ultra-Thin Films, and Long-Ribbons

Compared to the organic counterparts, chiral self-assembly of nanomaterials shows persistency to kinetic factors such as solvent environments, and consequently, dynamic modulation of self-assembly and functions remains major challenge. Here, it is shown that alkylated, chiral polymer dots (c-PDs) give highly ordered self-assemblies with amplified chirality adaptive to solvent environments, and one-to-many hierarchical aggregation can be realized. The c-PDs tended to self-assemble into nanohelices with cubic packing in the solid state, which, thanks to the thermo-responsiveness, transformed into thermic liquid crystals upon heating. Cotton effects and circularly polarized luminescence evidenced the chirality transfer from central chirality to supramolecular chirality. At the air-water interface, the c-PDs are self-assembled into monolayers, which further stack into multiple layers with chirality transfer and highly ordered packing. In addition, undergoing a good/poor solvent exchange, the c-PDs afforded ultra-long microribbons up to a length scale of millimeters, which are constituted by the bilayer lamellar stacking. The versatile chiral self-assembly modalities with long-range ordered packing arrays of carbonized c-PDs via solvent strategy are realized. This feature is comparable to the organic species, although the c-PDs have no atomic precise structures. This work would surely expand the applications of quantum dot ordered self-assembly with adaptiveness to kinetic factors.

Helical Crystals in Aliphatic Copolyesters: From Chiral Amplification to Mechanical Property Enhancement

We demonstrate herein a bottom-up strategy for achieving helical crystals via chiral amplification in copolyesters by incorporating a small amount of (d)-isosorbide into semicrystalline polyester, poly(ethylene brassylate) (PEB). During bulk crystallization of poly(ethylene-co-isosorbide brassylate)s, the molecular chirality of isosorbide in the amorphous region is transferred to PEB crystal chirality and amplified by the formation of right-handed helical crystals. Increasing isosorbide content or reducing crystallization temperature leads to thinner PEB lamellae crystals, strengthening chiral amplification by forming superhelices with a smaller helical pitch. Moreover, the superhelices with smaller helical pitch (larger chiral amplification) endow aliphatic copolyesters with enhanced modulus, strength, and toughness without sacrificing elongation-at-break. The principle outlined here could apply to the design of strong and tough materials.

Induced Circular Dichroism and Circularly Polarized Luminescence for Block Copolymers with Chiral Communications

Many sophisticated chiral materials are found in living organisms, giving specific functions and required complexity. Owing to the remarkable optical properties of chiral materials, they have drawn significant attention for the development of synthetic materials to give optical activities for appealing applications. In contrast to a top-down approach, the bottom-up approach from self-assembled systems with chiral host-achiral guest and achiral guest-chiral host for induced circular dichroism and induced circularly polarized luminescence has greatly emerged because of its cost-effective advantage with easy fabrication for mesoscale assembly. Self-assembled hierarchical textures with chiral sense indeed give significant amplification of the dissymmetry factors of absorption and luminescence (g_abs and g_lum ), resulting from the formation of well-ordered superstructures and phases with the building of chromophores and luminophores. By taking advantage of the microphase separation of block copolymers via self-assembly, a variety of well-defined chiral nanostructures can be formed as tertiary superstructures that can be further extended to quaternary phases in bulk or thin film. In this article, a conceptual perspective is presented to utilize the self-assembly of chiral block copolymers with chiral communications, giving quaternary phases with well-ordered textures at the nanoscale for significant enhancement of dissymmetry factors.

Fabrication of Multilayered Two-Dimensional Micelles and Fibers by Controlled Self-Assembly of Rod-Coil Block Copolymers

Fabricating hierarchical nanomaterials by self-assembly of rod-coil block copolymers attracts great interest. However, the key factors that affect the formation of the hierarchical nanomaterials have not been thoroughly researched. Herein, we have synthesized two diblock copolymers composed of poly(3-hexylthiophene) (P3HT) and polyethylene glycol (PEG). Through a heating, cooling, and aging process, a series of multilayered hierarchical micelles and fibers were prepared in alcoholic solutions. The transition from fibers to hierarchical micelles are strictly influenced by the strength of the π-π stacking interaction, the PEG chain length, and solvent. In isopropanol, the P3HT₂₂-b-PEG₄₃ could self-assemble into hierarchical micelles composed of several two-dimensional (2D) laminar layers, driven by the π-π stacking interaction and van der Waals force. The P3HT₂₂-b-PEG₄₃ could not self-assemble into well-defined nanostructures in methanol and ethanol, but could self-assemble into fibers in isobutanol. However, the P3HT₂₂-b-PEG₁₁₃ with a longer corona block only self-assembled into fibers in four alcoholic solutions, due to the increase in dissolving capacity and steric hindrance. The sizes and the size distributions of the nanostructures both increased with the increase in polymer concentration and the decrease in solvent polarity. This study shows a method to fabricate the hierarchical micelles.

Well-Ordered Nanonetwork Metamaterials from Block Copolymer Templated Syntheses

ConspectusThrough the morphological evolution to give highly optimized complex architectures at different length scales, fine-tuned textures for specific functions in living organisms can be achieved in nature such as a bone core with very complicated porous architecture to attain a significant structural efficiency attributed to delicately structured ligaments and density gradients. As inspired by nature, materials with periodic network structures (i.e., well-defined porous textures) in the nanoscale are appealing and promising for innovative properties. Biomimicking from nature, organic and/or inorganic nanonetworks can be synthetically fabricated, giving broadness and effectiveness when tuning the desired properties. Metamaterials are materials whose effective properties do not result from the bulk behavior of the constituent materials but rather mainly from their deliberate structuring. The performances of fabricating metamaterials will depend on the control of size, shape, order, and orientation of the forming textures. One of the appealing textures for the deliberate structuring is network architecture. Network materials possess self-supporting frameworks, open-cell character, high porosity, and large specific surface area, giving specific functions and complexity for diverse applications. As demonstrated by recent studies, exceptional mechanical performances such as negative thermal expansion, negative Poisson's ratio, and twisting under uniaxial forces can be achieved by the effect of the deliberate structuring with nanonetwork textures. In contrast to a top-down approach, a bottom-up approach is cost-effective, and also it can overcome the size limitation to reach nanoscale fabrication. It can be foreseen that network metamaterials with a feature size of tens of nanometers (referred as nanonetwork metamaterials) may provide new comprehension of the structure and property relationships for various materials. The self-assembly of block copolymers (BCPs) is one of the most used methods to build up well-ordered nanostructured phases from a bottom-up approach with precise control of size, shape, and orientation in the thin films for realistic applications. In this account, we summarize recent advancements in the fabrication of nanohybrids and nanoporous materials with well-ordered nanonetwork textures even with controlled helicity by combining block copolymer self-assembly and templated syntheses for mechanical and optical applications with superior properties beyond nature as metamaterials as well as chiral metamaterials with new properties for chiroptic applications such as chiral plasmonics, beam splitter, and negative refraction. The description of the fundamental facets of a nonconventional structure-property relationship with the characters of metamaterials and the state-of-the-art methodologies to fabricate nanonetworks using block copolymer self-assembly will stimulate research activities for the development of nanonetwork metamaterials with exceptional individual and multifunctional properties for futuristic devices.

Breaking Mirror Symmetry of Double Gyroids via Self-Assembly of Chiral Block Copolymers

Significant enhancement of segment-scale chirality, as measured by vibrational circular dichroism (VCD), is observed in the helical phase (H*) of polylactide-based chiral block copolymers (BCPs*) due to the mesoscale chirality of the microphase-separated domains. Here, we report a weaker, yet meaningful, enhancement on the VCD signal of a double gyroid phase (DG) as compared to a double diamond phase (DD) and disordered phase from the same diblock BCPs*. Residual VCD enhancement indicates a weak degree of chiral symmetry breaking, implying the formation of a chiral double gyroid (DG*) instead of the canonical achiral form. Calculations on the basis of orientational self-consistent field theory, comparing coupling between the segmental-scale preference of an intradomain twist and morphological chirality, show that a transition between DG and DG* takes place above the critical chiral strength, driving a weak volume asymmetry between the two enantiomeric single networks of DG*. The formation of nanostructures with controllable mesoscale chiral asymmetry indicates a pathway for the amplification of optical activity driven by self-assembly.

Crystallization of polylactides examined by vibrational circular dichroism of intra- and inter-chain chiral interactions

Herein, vibrational circular dichroism (VCD) measurements were carried out to study the kinetics of cold-crystallized poly(D-lactide) (PDLA) at the molecular level via qualitative analysis. The amplification of the VCD signals from intra- and inter-chain chiral interactions suggests the formation of partially ordered PDLA, followed by heterogeneous nucleation for crystallization. These results were further supported by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and Fourier transform infrared (FTIR) spectroscopy analyses.

From a single helix to a helical porous metalloenzyme catalyst based on temperature sensitive polyionic liquids

It is a challenging task to construct helical structures through the assembly of achiral polymers.

Achiral copper clusters helically confined in self-assembled chiral nanotubes emitting circularly polarized phosphorescence

Achiral Cu5− cluster coassembled with a chiral amphiphile to afford helical nanotubes, where the Cu5− cluster was confined within the nanotubes, forming helical arrangement with emerged chiroptical activities (CD and CPP), with a large gabs up to 0.018.

Artificial Chiral Interfaces against Amyloid-β Peptide Aggregation: Research Progress and Challenges

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by an imbalance between the production and clearance of amyloid-β (Aβ) species. AD not only influences the life quality of the patients but also heavily burdens the families and society. Therefore, it is an urgent mission to research and develop some new anti-amyloid aggregation drugs. In recent years, there were research and development of engineered nanostructures as Aβ amyloid inhibitors have attracted extensive attention and become a new frontier in nanomedicine. The effects of nanostructural surface properties (e.g., morphology, charge, hydrophobicity) on inhibition of Aβ aggregation are modulated by adsorbed Aβ peptides. Nevertheless, chirality has been seldom considered in recognition of Aβ species and modulation of Aβ aggregations. Moreover, a more relevant question for chiral inhibitors is little known about the molecular mechanism of how to interface chiral effects Aβ targeting recognition and effective mitigation of amyloidosis at the molecular level. Herein, we review recent experimental and theoretical results acquired in the specific areas of artificial chiral nanostructure inhibitors. This article will be essential to provide a microlevel insight into the effects of chiral nanointerfaces on amyloidosis processes as well as the development of chiral inhibitor drugs against Aβ fibrillation.

Chirality in peptide-based materials: From chirality effects to potential applications

Chirality is ubiquitous in nature with primary cellular functions that include construction of right-/left-handed helix and selective communications among diverse biomolecules. Of particularly intriguing are the chiral peptide-based materials that can be deliberately designed to change physicochemistry properties via tuning peptide sequences. Critically, understanding their chiral effects are fundamental for the development of novel materials in chemistry and biomedicine fields. Here, we review recent researches on chirality in peptide-based materials, summarizing relevant typical chiral effects towards recognition, amplification, and induction. Driven forces for the chiral discrimination in affinity interaction as well as the handedness preferences in supramolecular structure formation at both the macroscale and microscale are illustrated. The implementation of such chirality effects of artificial copolymers, assembled aggregates and their composites in the fields of bioseparation and bioenrichment, cell incubation, protein aggregation inhibitors, chiral smart gels, and bionic electro devices are also presented. At last, the challenges in these areas and possible directions are pointed out. The diversity of chiral roles in the origin of life and chirality design in different organic or composite systems as well as their applications in drug development and chirality detection in environmental protection are discussed.

Biased Symmetry Breaking and Chiral Control by Self-Replicating in Achiral Tetradentate Platinum (II) Complexes

Obtaining homochirality from biased symmetry-breaking of self-assembly in achiral molecules remains a great challenge due to the lack of ingenious strategies and controlling their handedness. Here, we report the first case of biased symmetry breaking from achiral platinum (II) liquid crystals which self-organize into an enantiomerically enriched single domain without selection of handedness in twist grain boundary TGB ^[ *^] phase. Most importantly, the chiral control of self-organization can be achieved by using above the homochiral liquid crystal films with determined handedness (P or M) as a template. Moreover, benefiting from self-assembled superhelix, these complexes exhibit prominent circularly polarized luminescence with high |g_lum | up to 3.4×10^-3 in the TGB ^[ *^] mesophase. This work paves a neoteric avenue for the development of chiral self-assemblies from achiral molecules.

Constructing helical nanowires via polymerization-induced self-assembly

While reliable strategies for constructing block copolymer (BCP) nanowires have been developed, helical nanowires are rarely reported in polymerization-induced self-assembly (PISA). Herein, in this work, a new strategy for constructing helical nanowires was developed via PISA mediated by a fluorinated stabilizer block. Ultralong nanowires with helical structure can be readily produced in a wide range of block compositions. In addition, the generality of this strategy was well testified by expanding monomer types. The achiral BCP nano-objects underwent a morphology transition from spheres to helical nanowires during aging. We believe this work will provide a general strategy for producing helical nanowires through PISA of achiral BCPs.

Enantiomeric Switching of the Circularly Polarized Luminescence Processes in a Hierarchical Biomimetic System by Film Tilting

Circularly polarized luminescence (CPL) switching has attracted great attention due to the potential applications in chiral photonics and electronics. However, the lack of examples to achieve switchable CPL within a single material in the dry solid state hampers the scope of applications. Herein, we demonstrate a crystalline chiral polymer film as a polarizing medium consisting of radially assembled twisted crystallites, where achiral aggregation-induced emissive luminogens (AIEgens) are confined between the twisted crystalline stacks, eventually yielding handedness-switchable CPL by simple film tilting. Hierarchically organized twisted crystallites create the selective reflection activity of the polarizing medium. Upon film tilting, enantiomeric switching is realized by selectively collecting transmitted and reflected CPL components. The confined AIEgens in the crystalline polarizing system show a great enhancement of the luminescence efficiency. Moreover, the approach is general with broadband activity, and various AIEgens could be applied to generate full-color-tunable CPL. Additionally, the rigid and continuous nature of this polarizing system affords enhanced optical stability and facile modulation, developing a general route for designing chiroptical materials.

On the Optical Activity of Poly(L-Lactic Acid) (PLLA) Oligomers and Polymer: Detection of Multiple Cotton Effect on Thin PLLA Solid Film Loaded with Two Dyes

Optical rotatory dispersion (ORD) is a beautiful analytical technique for the study of chiral molecules and polymers. In this study, ORD was applied successfully to follow the degree of polycondensation of l-(+)-lactic acid toward the formation of poly(lactic acid) oligomers (PLAO) and high molecular weight poly(L-lactic acid) (PLLA) in a simple esterification reaction equipment. PLLA is a biodegradable polymer obtainable from renewable raw materials. The racemization of the intrinsically isotactic PLLA through thermal treatment can be easily followed through the use of ORD spectroscopy. Organic or molecular electronics is a hot topic dealing with the combination of π-conjugated organic compounds and polymers with specific properties (e.g., chirality) which can be exploited to construct optoelectronic devices, such as organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) high efficiency cells, switchable chirality devices, organic field-effect transistors (OFETs), and so on. ORD spectroscopy was applied to study either the gigantic optical rotation of PLLA films, as well as to detect successfully the excitonic coupling, occurring in thin solid PLLA green film loaded with a combination of two dyes: SY96 (a pyrazolone dye) and PB16 (the metal-free phthalocyanine pigment). The latter compound PLLA loaded with SY96 and PB16 shows a really gigantic optical activity in addition to typical ORD signal due to exciton coupling and may be considered as a simple and easily accessible model composite of a chiral polymer matrix combined with π-conjugated dyes for molecular electronics studies.

Networks with controlled chirality via self-assembly of chiral triblock terpolymers

Nanonetwork-structured materials can be found in nature and synthetic materials. A double gyroid (DG) with a pair of chiral networks but opposite chirality can be formed from the self-assembly of diblock copolymers. For triblock terpolymers, an alternating gyroid (G^A) with two chiral networks from distinct end blocks can be formed; however, the network chirality could be positive or negative arbitrarily, giving an achiral phase. Here, by taking advantage of chirality transfer at different length scales, G^A with controlled chirality can be achieved through the self-assembly of a chiral triblock terpolymer. With the homochiral evolution from monomer to multichain domain morphology through self-assembly, the triblock terpolymer composed of a chiral end block with a single-handed helical polymer chain gives the chiral network from the chiral end block having a particular handed network. Our real-space analyses reveal the preferred chiral sense of the network in the G^A, leading to a chiral phase.

Spiral Hierarchical Superstructures from Twisted Ribbons of Self-Assembled Chiral Block Copolymers

Spiral hierarchical superstructures were found in the self-assembly of chiral block copolymers (BCPs*) composed of a chiral poly(l-lactide) (PLLA) and an achiral polystyrene (PS) as major and minor blocks, respectively. The PLLA helical chain with semiflexible rod-like character as compared to the random coil of PS results in self-assembly with a conformational asymmetry effect overwhelming the compositional one. Consequently, instead of the forming PS cylinder microdomains in the PLLA matrix, a smectic liquid-crystal-like bilayer sandwiched with PLLA and PS microdomains will be formed. Owing to twisting and bending due to the chiral cholesteric liquid-crystal-like force field combined with steric hindrance at the chiral interface, the forming bilayers (twisted ribbon) will develop into either a concentric lamellar texture from scrolling or roll-cake textures from spiraling. This study might bring a concept for the formation of spiral hierarchical superstructures from self-assembled bilayers for device application.

Secondary structure drives self-assembly in weakly segregated globular protein–rod block copolymers

Imparting secondary structure to the polymer block can drive self-assembly in globular protein–helix block copolymers, increasing the effective segregation strength between blocks with weak or no repulsion.

Mesochiral phases from the self-assembly of chiral block copolymers

Self-assembly of block copolymers with chiral sense gives mesochiral phases possessing helical sense. With the controlled chirality of the helical cylinder and chiral network, it is appealing to fabricate chiral materials for applications.