We report on the solution-state assembly of all-conjugated polythiophene diblock copolymers containing nonpolar (hexyl) and polar (triethylene glycol) side chains. The polar substituents provide a large contrast in solubility, enabling formation of stably suspended crystalline fibrils even under very poor solvent conditions for the poly(3-hexylthiophene) block. For appropriate block ratios, complexation of the triethylene glycol side chains with added potassium ions drives the formation of helical nanowires that further bundle into superhelical structures.

http://absimage.aps.org/image/MAR11/MWS_MAR11-2010-005155.pdf

Hierarchical Helical-Assembly of Conjugated Poly(3-hexylthiophene)- b-poly(3-triethylene glycol-thiophene) Diblock Copolymers

Self-assembly, as a typical bottom-up strategy for the fabrication of functional materials, has been applied to fabricate chiral materials with subtle chiral nanostructures. The chiral nanostructures exhibit great potential in asymmetric catalysis, chiral sensing, chiral electronics, photonics, and even the realization of several biological functions. According to existing studies, the supramolecular chirality transfer process combined with hierarchical self-assembly plays a vital role in the fabrication of multiscale chiral structures. This progress report focuses on the hierarchical self-assembly of chiral or achiral molecules that aggregate with asymmetric spatial structures such as twisted bands, helices, and superhelices in different environments. Herein, recent studies on the chirality transfer induced self-assembly based on a variety of supramolecular interactions are summarized. In addition, the influence of different environments and the states of systems including solutions, condensed states, gel systems, interfaces on the asymmetric hierarchical self-assembly, and the expression of chirality are explored. Moreover, both the driving forces that facilitate chiral bias and the supramolecular interactions that play an important role in the expression, transfer, and amplification of the chiral sense are correspondingly discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202002132

Supramolecular Chirality Transfer toward Chiral Aggregation: Asymmetric Hierarchical Self-Assembly

Circularly polarized luminescent (CPL) materials are currently drawing ever-increasing interest. This contribution reports the first success in simply combining chiral helical substituted polyacetylenes (HSPAs) with achiral luminophores to fabricate CPL materials demonstrating a high dissymmetry factor (glum) up to 10–1, despite neither covalent nor noncovalent interactions occurring between the two components. Circularly polarized scattering and fluorescence-selective absorption mechanisms are proposed for the generation of CPL, and a “matching rule” is further established for selecting chiral polymers and achiral luminophores for the purpose. Taking advantage of the circularly polarized scattering effect, full-color tunable CPL materials are prepared from the combination of achiral fluorescent dyes and chiral HSPAs. Following the fluorescence-selective absorption mechanism, functional composite films with on–off and switchable CPL performance are fabricated. Also, remarkably, the glum value in the prepa...

Combining Chiral Helical Polymer with Achiral Luminophores for Generating Full-Color, On–Off, and Switchable Circularly Polarized Luminescence

Introducing fluorescent chromophores to helical architectures can generate circularly polarized luminescence (CPL). Herein, a series of fluorescent chiral helical monosubstituted polyacetylenes showing both intense optical activity and CPL are prepared by copolymerizing achiral fluorescent acetylenic monomer and a chiral monomer. The luminescence dissymmetry factor (glum) values of the obtained copolymers can reach up to +0.136 and −0.264. The formation of predominantly one-handed helical structures in the copolymer backbones has proved to play crucial roles in achieving the intense CPL. The dynamic helical polymer chains further enable the CPL-active materials to exhibit both solvent sensitivity and temperature sensitivity. Moreover, the helical polymer structures can also helpfully restrain the aggregation-caused quenching (ACQ) effect of fluorescent groups. Therefore, the helical polymers play double roles: providing helical chirality for generating CPL and simultaneously circumventing ACQ effect of ch...

Intense Circularly Polarized Luminescence Contributed by Helical Chirality of Monosubstituted Polyacetylenes

The first example of luminescent monosubstituted polyacetylenes (mono-PAs) is presented, based on a contracted cis-cisoid polyene backbone. It has an excellent circularly polarized luminescence (CPL) performance with a high dissymmetric factor (up to the order of 10-1 ). The luminescence stems from the helical cis-cisoid PA backbone, which is tightly fixed by the strong intramolecular hydrogen bonds, thereby reversing the energy order of excited states and enabling an emissive energy dissipation. CPL switches are facilely achieved by the solvent and temperature through reversible conformational transition. By taking advantages of fast response and high sensitivity, the thin film of mono-PAs could be used as a CPL-based probe for quantitative detection of trifluoroacetic acid with a wider linear dynamic range than those of photoluminescence and circular dichroism. This work opens a new avenue to develop novel smart CPL materials through modulating conformational transition.

Brightening up Circularly Polarized Luminescence of Monosubstituted Polyacetylene by Conformation Control: Mechanism, Switching, and Sensing

Optically active helical random copoly(phenylacetylene)s were prepared from structurally similar monomers, (+)-3-hexadecylcarbamoyl-5-[((S)-1-phenylethyl)carbamoyl]phenylacetylene and 3-hexadecylcarbamoyl-5-(benzylcarbamoyl)phenylacetylene, under the catalysis of Rh[C(C6H5)═C(C6H5)2](nbd)(4-FC6H4)3P (nbd = 2,5-norbornadiene). The chiral amplification followed either normal or abnormal “sergeants-and-soldiers” rule depending on the solvent nature. In apolar solvents (i.e., CHCl3 and THF), contracted cis-cisoid M- and P-helices were selectively induced for the copolymers containing chiral units below or above 74 mol %, respectively. In polar solvent (i.e., CHCl3/CH3OH, 70/30, v/v), a cis-cisoid to cis-transoid transition occurred and stretched M-helices were dominantly formed, the optical activity of which scaled up nonlinearly with increasing chiral component. This unusual phenomenon was rationalized by the distinct competing interactions between the vicinal chiral/achiral and chiral/chiral unit pairs in t...

Conformation Shift Switches the Chiral Amplification of Helical Copoly(phenylacetylene)s from Abnormal to Normal ``Sergeants-and-Soldiers'' Effect

A pair of enantiomeric cis-poly(phenylacetylene)s (PPAs) substituted at the meta-positions of pendant phenyl rings by an achiral methoxycarbonyl group and a chiral 1-methylpropyloxycarbonyl group (i.e., sP-Me-C4/rP-Me-C4) as well as two cis-PPAs bearing either just a methoxycarbonyl (i.e., m-aP-Me) or a 1-methylpropyloxycarbonyl (i.e., m-sP-C4) meta substituent were synthesized under the catalysis of [Rh(nbd)Cl]2 (nbd = norbornadiene). Various techniques including 1H NMR, FTIR, Raman, UV–vis, CD, DSC, STM, DLS/SLS, and computer calculation were applied to characterize the helical structures of these polymers in both solution and solid states. sP-Me-C4/rP-Me-C4 adopted contracted cis-cisoid helical conformations in THF, toluene, CH2Cl2, and ClCH2CH2Cl but cis-transoid ones in CHCl3 and Cl2CHCHCl2. The cis-cisoid helices were considered to be stabilized by the existence of six n → π* interaction bands along the polyene backbones between vicinal carbonyl groups. Such interactions were insensitive to the diel...

Cis-Cisoid Helical Structures of Poly(3,5-disubstituted phenylacetylene)s Stabilized by Intramolecular n → π* Interactions

A novel series of amphiphilic rod–rod block copolymers (PPAm-b-PrmEOn) based on achiral phenylacetylene (PA) and chiral 3,5-disubstituted phenylacetylene (rmEO) were synthesized through sequential living polymerizaitons using the catalyst Rh[C(C6H5)═C(C6H5)2](nbd)(4-FC6H4)3P (nbd = norbornadiene) (Rh-cat) The living nature of the polymerization of rmEO using Rh-cat was proved These block copolymers consist of a hydrophobic achiral stretched cis–transoid helical PPA block and a hydrophilic one-handed contracted cis–cisoid helical PrmEO block The amphiphilic block copolymers could self-assemble into well-defined aggregates in THF/H2O The effects of the composition of block copolymers, water contents, and initial copolymer concentration on the formation of aggregates were investigated The block copolymers with short corona-forming blocks formed vesicles, while those with long corona-forming blocks formed novel multiarm worm-like micelles As the water content increased, the aggregates transformed from t

Amphiphilic Rod–Rod Block Copolymers Based on Phenylacetylene and 3,5-Disubstituted Phenylacetylene: Synthesis, Helical Conformation, and Self-Assembly

The cis-trans isomerization of amides plays a vital role in all kinds of structural changes and biological activities, involving protein folding, protein misfolding, and even protein molecular reco...

Ge Shi

Papers

Brightening up Circularly Polarized Luminescence of Monosubstituted Polyacetylene by Conformation Control: Mechanism, Switching, and Sensing

Conformation Shift Switches the Chiral Amplification of Helical Copoly(phenylacetylene)s from Abnormal to Normal ``Sergeants-and-Soldiers'' Effect

Cis-Cisoid Helical Structures of Poly(3,5-disubstituted phenylacetylene)s Stabilized by Intramolecular n → π* Interactions

Amphiphilic Rod–Rod Block Copolymers Based on Phenylacetylene and 3,5-Disubstituted Phenylacetylene: Synthesis, Helical Conformation, and Self-Assembly

Thermoswitching of Helical Inversion of Dynamic Polyphenylacetylenes through cis-trans Isomerization of Amide Pendants