Responsive hydrogels applied in the biomedical area show great potential as synthetic extracellular matrix mimics and as host medium for cell growth. The hydrogels often lack the characteristic mechanical properties that are typically seen for natural gels. Here, we demonstrate the unique responsive and mechanical properties of hydrogels based on oligo(ethylene glycol) functionalized polyisocyanopeptides. These stiff helical polymers form gels upon warming at concentrations as low as 0.006 %-wt polymer, with materials properties almost identical to those of their intermediate filaments, a class of cytoskeletal proteins. Using a combination of macroscopic rheology and molecular force microscopy the hierarchical relationship between the macroscopic behaviour of theses peptide mimics has been correlated with the molecular parameters.

The use of bottom-up approaches to construct patterned surfaces for technological applications is appealing, but to date is applicable to only relatively small areas (approximately 10 square micrometers). We constructed highly periodic patterns at macroscopic length scales, in the range of square millimeters, by combining self-assembly of disk-like porphyrin dyes with physical dewetting phenomena. The patterns consisted of equidistant 5-nanometer-wide lines spaced 0.5 to 1 micrometers apart, forming single porphyrin stacks containing millions of molecules, and were formed spontaneously upon drop-casting a solution of the molecules onto a mica surface. On glass, thicker lines are formed, which can be used to align liquid crystals in large domains of square millimeter size.

We have investigated in detail the self-assembly of a chiral porphyrin trimer in different solvents and correlated this behavior to the aggregation of the molecule at a solid-liquid interface. In n-hexane and cyclohexane, CD spectroscopy and dynamic and static light scattering studies showed that the porphyrin trimer self-assembles already at micromolar concentrations into long, chiral supramolecular polymers, which precipitate as fibers when the solution is drop-cast onto a mica surface. In contrast, in chloroform, the compound is molecularly dissolved up to concentrations of 0.2 mM and when micromolar solutions are drop-cast onto mica, no precipitation of large assemblies occurs. Instead, at the moment that the chloroform film becomes subject to spinodal dewetting and the porphyrin trimers within this film start to self-assemble, extended patterns of equidistant lines of single molecule thick columnar stacks are formed.

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