Cyano-Substituted Oligo(p-phenylene vinylene) Derivatives with Aggregation-Induced Enhanced Emissions and Mechanofluorochromic Luminescence

Developing red fluorescence emitters with simple structures via convenient synthetic routes is highly desirable yet challenging. Herein, two novel donor-acceptor-type red emitters, DCFOPV-TPA and SCFOPV-TPA, featuring the intramolecular charge transfer effect were designed by integrating triphenylamine and trifluoromethyl into a CN-substituted oligo(p-phenylene vinylene) backbone. Both chromophores exhibited aggregation-induced enhanced emission and solvatochromic behavior. Moreover, DCFOPV-TPA also displayed reversible mechanofluorochromic properties under external force.

Control of Properties through Hydrogen Bonding Interactions in Conjugated Polymers

Molecular design is crucial for endowing conjugated polymers (CPs) with unique properties and enhanced electronic performance. Introducing Hydrogen-bonding (H-bonding) into CPs has been a broadly exploited, yet still emerging strategy capable of tuning a range of properties encompassing solubility, crystallinity, electronic properties, solid-state morphology, and stability, as well as mechanical properties and self-healing properties. Different H-bonding groups can be utilized to tailor CPs properties based on the applications of interest. This review provides an overview of classes of H-bonding CPs (assorted by the different H-bond functional groups), the synthetic methods to introduce the corresponding H-bond functional groups and the impact of H-bonding in CPs on corresponding electronic and materials properties. Recent advances in addressing the trade-off between electronic performance and mechanical durability are also highlighted. Furthermore, insights into future directions and prospects for H-bonded CPs are discussed.

Synthesis and folding behaviour of poly(p-phenylene vinylene)-based β-sheet polychromophores

This contribution describes the design and synthesis of β-sheet-mimicking synthetic polymers comprising distinct poly(p-phenylene vinylene) (PPV) and poly(norbornene) (PNB) backbones with multiple turns.

This contribution describes the design and synthesis of β-sheet-mimicking synthetic polymers comprising distinct poly(p-phenylene vinylene) (PPV) and poly(norbornene) (PNB) backbones with multiple turns. The rod–coil–coil–rod tetrablock copolymers, synthesized using ring-opening metathesis polymerization (ROMP) and featuring orthogonal face-to-face π–π stacking and phenyl/perfluorophenyl interactions, show persistent folding both in bulk and at the single molecule level, irrespective of the number of β-turns. Single molecule polarization studies reveal that the copolymers are more anisotropic than the corresponding homopolymers. Examination of the spectral signatures of the single molecules shows a dominant emissive chromophore in the linked materials compared to the homopolymer. The lack of significant spectral changes of the folded materials along with the existence of a dominant emission spectrum supports the proposed structure of well-aligned, minimally-interacting chromophores. Utilization of this reliably folding, phenyl/perfluorophenyl functionality could provide an extremely useful tool in future functional materials design.

Morphological Control of Coil-Rod-Coil Molecules Containing m-Terphenyl Group: Construction of Helical Fibers and Helical Nanorings in Aqueous Solution

Rod-coil molecules, composed of rigid segments and flexible coil chains, have a strong intrinsic ability to self-assemble into diverse supramolecular nanostructures. Herein, we report the synthesis and the morphological control of a new series of amphiphilic coil-rod-coil molecular isomers 1-2 containing flexible oligoether chains. These molecules are comprised of m-terphenyl and biphenyl groups, along with triple bonds, and possess lateral methyl or butyl groups at the coil or rod segments. The results of this study suggest that the morphology of supramolecular aggregates is significantly influenced by the lateral alkyl groups and by the sequence of the rigid fragments in the bulk and in aqueous solution. The molecules with different coils self-assemble into lamellar or oblique columnar structures in the bulk state. In aqueous solution, molecule 1a, with a lack of lateral groups, self-assembled into large strips of sheets, whereas exquisite nanostructures of helical fibers were obtained from molecule 1b, which incorporated lateral methyl groups between the rod and coil segments. Interestingly, molecule 1c with lateral butyl and methyl groups exhibited a strong self-organizing capacity to form helical nanorings. Nanoribbons, helical fibers, and small nanorings were simultaneously formed from the 2a-2c, which are structural isomers of 1a, 1b, and 1c. Accurate control of these supramolecular nanostructures can be achieved by tuning the synergistic interactions of the noncovalent driving force with hydrophilic-hydrophobic interactions in aqueous solution.

Effects of molecular architecture on morphology and photophysics in conjugated polymers: from single molecules to bulk

A definitive comprehension of morphology and photophysics in conjugated polymers at multiple length scales demands both single molecule spectroscopy and well-controlled molecular architectures.

Conjugated polymers (CPs) possess a wide range of desirable properties, including accessible energetic bandgaps, synthetic versatility, and mechanical flexibility, which make them attractive for flexible and wearable optoelectronic devices. An accurate and comprehensive understanding about the morphology–photophysics relations in CPs lays the groundwork for their development in these applications. However, due to the complex roles of chemical structure, side-chains, backbone, and intramolecular interactions, CPs can exhibit heterogeneity in both their morphology and optoelectronic properties even at the single chain level. This molecular level heterogeneity together with complicated intermolecular interactions found in bulk CP materials severely obscures the deterministic information about the morphology and photophysics at different hierarchy levels. To counter this complexity and offer a clearer picture for the properties of CP materials, we highlight the approach of probing material systems with specific structural features via single molecule/aggregate spectroscopy (SMS). This review article covers recent advances achieved through such an approach regarding the important morphological and photophysical properties of CPs. After a brief review of the typical characteristics of CPs, we present detailed discussions of structurally well-defined model systems of CPs, from manipulated backbones and side-chains, up to nano-aggregates, studied with SMS to offer deterministic relations between morphology and photophysics from single chains building up to bulk states.