Self-Assembled Polythiophene-Based Nanostructures: Numerical Studies

Supramolecular polymerization: challenges and advantages of various methods in assessing the aggregation mechanism

Oligothiophenes with branched alkyl end groups show distinct aggregation in organic solvents. The process of supramolecular polymerization is assessed by three different methods (UV-vis absorption and fluorescence emission spectroscopy and dynamic light scattering) to exclude artifacts. An apparent dependence of the degree of aggregation on the concentration of the oligomers is observed. Above the upper limit of concentration (a lower micromolar range for the present class of compounds), experimental data delivered conflicting results and the concentration should not therefore be exceeded. Scanning force microscopy and molecular dynamics simulations confirm the formation of one-dimensional aggregates with presumably helical arrangement of the achiral monomers.

Structure of P3HT crystals, thin films, and solutions by UV/Vis spectral analysis

The shift in the absorption spectrum of P3HT when comparing solution, spin-coated thin films, and the bulk crystal can be reproduced by multiscale simulation and explained in terms of the degree of intramolecular torsion.

Self-assembling nanofibers from thiophene-peptide diblock oligomers: a combined experimental and computer simulations study

We report herein the synthesis of a novel type of hybrid compound that consists of a poly(ethylene oxide) (PEO) functionalized β-sheet peptide sequence covalently linked to an alkylated quaterthiophene moiety. Compounds of this class are highly promising for technological applications because their self-assembly and stimuli-responsive behavior, which is mainly caused by the peptide moieties, combined with the potential semiconducting properties of oligothiophenes provides unprecedented opportunities for the design of advanced materials at the nanoscale in such areas as, for example, organic electronics and sensor design for chemical and biomedical applications. The compound presented herein is experimentally shown to form stable fibrillar aggregates that are visualized by both transmission electron and atomic force microscopy. We developed a theoretical methodology to study the possible intermolecular arrangements and their characteristic features with the help of all-atom MD simulations, while simultaneously incorporating available experimental data into the model. Large-scale atomistic simulations of several fibrillar aggregates with different molecular arrangements were performed. The results of the simulations are compared with experimental data, which leads to the proposition of a likely model for the arrangement of the individual molecules within the observed aggregates.

Self-organizing bioinspired oligothiophene-oligopeptide hybrids

In this minireview, we survey recent advances in the synthesis, characterization, and modeling of new oligothiophene-oligopeptide hybrids capable of forming nanostructured fibrillar aggregates in solution and on solid substrates. Compounds of this class are promising for applications because their self-assembly and stimuli-responsive properties, provided by the peptide moieties combined with the semiconducting properties of the thiophene blocks, can result in novel opportunities for the design of advanced smart materials. These bio-inspired molecular hybrids are experimentally shown to form stable fibrils as visualized by AFM and TEM. While the experimental evidence alone is not sufficient to reveal the exact molecular organization of the fibrils, theoretical approaches based on quantum chemistry calculations and large-scale atomistic molecular dynamics simulations are attempted in an effort to reveal the structure of the fibrils at the nanoscale. Based on the combined theoretical and experimental analysis, the most likely models of fibril formation and aggregation are suggested.