Polymer, heal thyself! Supramolecular ABA triblock copolymers formed by dimerization of 2-ureido-4-pyrimidinone (UPy) end-functionalized polystyrene-b-poly(n-butyl acrylate) (PS-b-PBA) AB diblock copolymers have been synthesized, resulting in a self-healing material that combines the advantageous mechanical properties of thermoplastic elastomers and the dynamic self-healing features of supramolecular materials.

A strong beta-sheet forming peptide was conjugated to PEO and utilized to guide the structure formation process toward well-defined, tape-like structures with millimeters in length, about 2 mum width, and approximately 50 nm height. The aggregation tendency of the peptide was temporarily suppressed for ease of synthesis by the integration of multiple switch-peptide defect segments into the peptide backbone. A subsequent rearrangement in the defects re-establishes the native peptide backbone and triggers the assembly by switching the aggregation properties on.

Synthesis and peptide-guided self-assembly of an organo-soluble peptide-polymer conjugate, comprising a sequence-defined polypeptide and a poly(n-butyl acrylate), are described. The amino acid sequence of the peptide encodes a high tendency to adopt an antiparallel beta-sheet motif, and thus programs the formation of tapelike microstructures. Easy synthesis and controllable self-assembly is ensured by the incorporation of structure breaking switch defects into the peptide segment. This suppresses temporarily the aggregation tendency of the conjugate as shown by circular dichroism, infrared spectroscopy (FT-IR), and atomic force microscopy (AFM). A pH-controlled rearrangement in the switch segments restores the native peptide backbone, triggering the self-assembly process and leading to the formation of densely twisted tapelike microstructures as could be observed by AFM and transmission electron microscopy. The resulting helical superstructures, when deposited on a substrate, are 2.9 nm high, 10 nm wide, and up to 2.3 mum long. The helical pitch is about 37 nm, and the pitch angle is 48 degrees . The helical superstructures undergo defined entanglement to form superhelices, leading to the formation of soft, continuous organo-gels. A twisted two-dimensional core-shell tape is proposed as a structure model, in which the peptide segments form an antiparallel beta-sheet with a polymer shell.

Investigation of self-organization behavior of organic (semi)-conductors became very important recently, since their physical properties and performance in organic electronic devices strongly depend on ordering effects, on both molecular and nanoscale levels. [1] In this respect, bioinspired functionalization of conjugated systems might greatly enhance the diversity of electronically interesting assemblies, and potentially allow for the rational design of hierarchically ordered nanostructures.[2] Thus, from possible hybrids of conjugated backbones, the combination of oligo-or polythiophenes with biomolecules, such as nucleotides, [3] carbohydrates, [4] or peptides, [5] are interesting. Particularly, the latter appears to be attractive, because interplay between different intermolecular forces in the peptide and oligothiophene segments results in competing self-assembly motifs. Hence, very specific organization properties can be expected. Whereas thiophene-based materials typically form well-organized 2D lamellar superstructures due to van der Waals interactions of alkyl side chains, and stack into the third dimension via p-p interactions, [6] secondary structures of peptides, preferentially bsheets or a-helices, are governed by stronger and directed hydrogen-bond formation.[7] The high tendency of peptides to adopt well-defined secondary-structure motifs has been exploited recently to guide self-organization of a broad range of synthetic polymers.[8] Attention has mainly been devoted to the b-sheet motif, leading to anisotropic fibrillar or fiber-like structures. [9] However, other highly interesting assembly motifs, for example the coiled-coil motif, were exploited, resulting in distinct nanoobjects by the lateral assembly of amphiphilic a-helices. [10] We recently presented the first conjugate between a regioregularly alkylated quaterthiophene and a pentapeptide consisting of a silk-inspired sequence of alanine-glycine repeats, which is known to adopt b-sheet structures.[5a] Unexpected and novel 3D nanostructures were found, suggesting that short peptide sequences may indeed influence the nanoscale structure, and ultimately, properties of organic semiconducting materials.The versatility of this class of hybrid oligo-/polymers is certainly not exploited, considering the diversity of both the conjugated oligo-/polymer platforms and the bioorganic segments. It becomes increasingly evident that such materials will envelop by far more structural and functional space as, for example, common AB-block copolymer systems.[11]Here, we present the synthesis and self-organization behavior of a symmetrically substituted A-B-A-type bioinspired semiconductor, quaterthiophene-peptide hybrid 8 (Scheme 1b), by combining a central quaterthiophene segment (B) with two peptide-poly(ethylene oxide) bioconjugates (A).As outlined in Scheme 1, the oligothiophene segment was substituted on both sides with an amino acid sequence Gly-(ThrVal) 3 -Gly-aPhe-Gly (Scheme 1, structure 2), with Gly ¼ glycine, Val ¼ valine, Thr ¼ threonine, ...