Individually separated supramolecular polymer chains toward solution-processable supramolecular polymeric materials

Herein, we present a simple design concept for a monomer that affords individually separated supramolecular polymer chains. Random introduction of alkyl chains with different lengths onto a monomer prevented its supramolecular polymers from bundling, permitting the preparation of concentrated solutions of the supramolecular polymer without gelation, precipitation, or crystallization. With such a solution in hand, we succeeded in fabricating self-standing films and threads consisting of supramolecular polymers

Two‐Dimensional Living Supramolecular Polymerization: Improvement in Edge Roughness of Supramolecular Nanosheets by Using a Dummy Monomer

Supramolecular polymers are formed through nucleation (i. e., initiation) and polymerization processes, and kinetic control over the nucleation process has recently led to the realization of living supramolecular polymerization. Changing the viewpoint, herein we focus on controlling the polymerization process, which we expect to pave the way to further developments in controlled supramolecular polymerization. In our previous study, two-dimensional living supramolecular polymerization was used to produce supramolecular nanosheets with a controlled area; however, these had rough edges. In this study, the growth of the nanosheets was controlled by using a ‘dummy’ monomer to produce supramolecular nanosheets with smoothed edges

Molecular and electronic structure investigation of encapsulated polytiophenes

Insulated molecular wires (IMWs) are expected to be applied to various optoelectronic applications due to their unique photophysical, electronic, and mechanical properties which originate from the absence of -stacking.[1] Kazunori et al have succeeded in the synthesis of a self-threading polythiophene with a polyrotaxane-like 3D architecture (PSTB, see Figure 1a), for which an intrawire hole mobility of 0.9 cm2 V−1 s−1 has been measured.[2] In this study we aim to evaluate for the first time the extension of the -conjugation in encapsulated polythiophenes. A comparison between the experimental Raman spectra of the self-threading PSTB polymer with their correspondent oligomers (i.e. 2STB-5STB) suggests that the effective conjugation length in the polymer is longer than five monomer units. Whether the effective conjugation length of the polymer is better described by using the long oligomer extrapolation approach or periodic DFT calculations of the polymer is discussed in detailed by exploiting the very recent potentialities of state-of-the-art quantum chemical simulations of vibrational properties for crystalline solids.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Raman Fingerprints of π-Electron Delocalization in Polythiophene-Based Insulated Molecular Wires

Insulated polythiophenes with a polyrotaxane-like 3D architecture have shown excellent intrawire hole mobility, allowing their use in interesting optoelectronic applications. This is due to the isolation of the π-conjugated backbones that warrants for stabilization of the quasi-planar conformation of the polythiophene core and prevents electronic communication between adjacent chains. Thus, polythiophene-based insulated molecular wires (IMWs) constitute ideal test-beds to evaluate the structural changes within the conjugated polymer chain, such as intrachain conformation and π-electron delocalization. Here, we investigate the structure and spectroscopic response of fully and partially insulated polythiophene-based IMWs. An experimental investigation of Raman spectra supported by density functional theory (DFT) calculations allows us to give a detailed interpretation of intramolecular interactions, highlighting differences in π-electron conjugation revealed by the presence of an intensity transfer between the two main Raman modes associated with the C═C/C–C stretching vibrations. This study proves the sensitivity of Raman spectroscopy as a technique to monitor structural changes in self-encapsulated conjugated polymers.This work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00) and Junta de Andalucía (UMA18-FEDERJA-080, P09FQM-4708, and P18-FR-4559) projects. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) Center of the University of Malaga. Funding for open access charge: Universidad de Málaga / CBUA

Supramolecular double-stranded Archimedean spirals and concentric toroids

Connecting molecular-level phenomena to larger scales and, ultimately, to sophisticated molecular systems that resemble living systems remains a considerable challenge in supramolecular chemistry. To this end, molecular self-assembly at higher hierarchical levels has to be understood and controlled. Here, we report unusual self-assembled structures formed from a simple porphyrin derivative. Unexpectedly, this formed a one-dimensional (1D) supramolecular polymer that coiled to give an Archimedean spiral. Our analysis of the supramolecular polymerization by using mass-balance models suggested that the Archimedean spiral is formed at high concentrations of the monomer, whereas other aggregation types might form at low concentrations. Gratifyingly, we discovered that our porphyrin-based monomer formed supramolecular concentric toroids at low concentrations. Moreover, a mechanistic insight into the self-assembly process permitted a controlled synthesis of these concentric toroids. This study both illustrates the richness of self-assembled structures at higher levels of hierarchy and demonstrates a topological effect in noncovalent synthesis

Effect of Conjugated Backbone Protection on Intrinsic and Light-Induced Fluorescence Quenching in Polythiophenes

Polythiophenes (PTs), particularly regioregular poly(3-hexylthiophene-2,5-diyl) (rr-P3HT), are important materials in photo-voltaics. The photophysical properties of PTs are still poorly understood, because of their aggregation tendency and formation of interchain species which can be avoided by insulating the conjugated backbone via self-threading. We investigated two polymers, rr-P3HT and its insulated analog, imbedded in PMMA at low concentrations. The exciton decay dynamics and fluorescence quantum yield were analyzed as a function of excitation power densities over the range from 1 x 10(-4) to 100 W/cm(2). For both polymers, substantial (up to S times) photoinduced fluorescence quenching was observed owing to singlet-triplet annihilation and quenching by other long-living charged photoproducts. We found that chain insulation eliminates static (or ultrafast) fluorescence quenching, but has no effect on slow dynamic quenching at time scales longer than 10 ps. We propose that static quenching is solely due to chain aggregation, whereas the dynamic quenching is a consequence of intrachain processes

Synthesis and Fluorescence Resonance Energy Transfer Properties of an Alternating Donor–Acceptor Copolymer Featuring Orthogonally Arrayed Transition Dipoles along the Polymer Backbone

We have synthesized a new entity of polymer structures composed of π-conjugated molecules: alternating donor–acceptor (D–A) copolymers featuring orthogonally arrayed transition dipoles along the polymer backbone. Such a unique structure could lead to novel functional fluorescent materials; therefore, we examined fluorescence resonance energy transfer (FRET) properties of the D–A copolymers using absorption, fluorescence, and fluorescence lifetime measurements based on the principle of FRET. The results suggested that the orthogonal and alternating D–A copolymer could potentially lead to a new FRET system in which the efficiency is sensitive to the polymer conformation

Electrochemical Generation and Spectroscopic Characterization of Charge Carriers within Isolated Planar Polythiophene

In order to unveil the nature of charge carriers in a doped polythiophene, a sterically isolated polythiophenene, poly­(<b>1EDOT</b>), was electrochemically synthesized on electrodes. Generation of charge carriers was induced upon controlled electrochemical doping and investigated through various spectroscopic methods; the charge carriers were identified based on spin concentration (ESR spectra), aromatic character (Raman spectra), and electronic transition (UV–vis–NIR absorption spectra) of the polythiophene. Peculiarity of this study lies in the fact that the electrochemistry of the poly­(<b>1EDOT</b>) reflects the p-doping process of a single polythiophene wire because interwire interaction (i.e., π–π stacking) is effectively prevented; therefore, the results should be essential and informative to understand polythiophene-based materials and devices. Upon electrochemical doping, ESR active polarons were generated. Further doping concentrated the polarons, which led to the formation of polaron pairs. Eventually, the polaron pairs merged into bipolarons at the doping level of about 30–35%. Such a transformation of charge carriers under different doping levels has been extrapolated from studies using oligomeric model compounds. To the best of our knowledge, this is the first example addressing the nature of the charge carriers generated in a single polythiophene wire by exploiting the unique structure of the isolated polythiophene. Importantly, the comparison of poly­(<b>1EDOT</b>) with common polythiophenes such as poly­(3,4-ethylenedioxythiophene) (i.e., poly<b>EDOT</b>) implied that π–π stacking strongly affects the generation and stability of charge carriers. Furthermore, we found that the polaron pair plays an important role in charge hopping transport in the conduction mechanism