No abstract

A rapid and universal approach for multifunctional material coatings was developed based on a mussel-inspired dendritic polymer. This new kind of polymer mimics not only the functional groups of mussel foot proteins (mfps) but also their molecular weight and molecular structure. The large number of catechol and amine groups set the basis for heteromultivalent anchoring and crosslinking. The molecular weight reaches 10 kDa, which is similar to the most adhesive mussel foot protein mfp-5. Also, the dendritic structure exposes its functional groups on the surface like the folded proteins. As a result, a very stable coating can be prepared on virtually any type of material surface within 10 min by a simple dip-coating method, which is as fast as the formation of mussel byssal threads in nature.

The electrocatalytic activity of a bimetallic Pt0.5Ru0.5N(Oct4)Cl colloid toward the oxidation of CO and a CO/H2 gas mixture (simulated reformer gas) was measured. The particle size distribution with a mean diameter of 1.7 ± 0.5 nm was determined by high-resolution transmission electron microscopy, and the formation of stoichiometrically alloyed particles was verified by point-resolved energy dispersive X-ray analysis. The CO-stripping voltammetry of glassy carbon supported Pt0.5Ru0.5 clusters was found to be in excellent agreement with CO-stripping voltammetry data measured on well-characterized bulk alloy electrodes. The activity of the colloid toward the continuous oxidation of 2% CO in H2 was assessed in a rotating disk electrode configuration at 25 °C in 0.5 M H2SO4, leading to the conclusion that PtRu colloids are a promising route toward the preparation of bimetallic high-surface-area fuel cell catalysts.

Ultrathin films of a symmetrical polystyrene-block-poly(2-vinylpyridine) diblock copolymer with a degree of polymerization of 600 were prepared by spin coating from a nonselective solvent, i.e., CHCl3, on mica. The concentration of the casting solutions was chosen to be too low to allow homogeneous coverage of the substrate without significant stretching of the macromolecules. Scanning force microscopy demonstrated the formation of uniform polystyrene clusters with a height of about 5 nm and a distance of about 100 nm between them. In between the substrate was covered by ≈1 nm thick film of poly(2-vinylpyridine). The large periodicity of the two-dimensional phase pattern is explained by the strong interaction of poly(2-vinylpyridine) with mica, favoring a highly stretched conformation. X-ray photoelectron spectroscopy showed that about every third poly(2-vinylpyridine) unit was in chemical contact with the substrate. When the film thickness was increased, the X-ray photoelectron spectroscopy N(1s) signal decreased in comparison to the C(1s) signal indicating that the adsorbed poly(2-vinylpyridine) got increasingly covered by polystyrene. An estimation of the free energy indicates that the lateral phase separation is mainly controlled by the length of the polystyrene blocks affecting the incompatibility of the polystyrene and the poly(2-vinylpyridine) covered mica.

Material-independent and bioinert hierarchical polymer multilayer coatings are presented. Chemically active catecholic hyperbranched polyglycerols (hPGs) form a foundation layer on a versatile surface via multivalent anchoring and crosslinking, the activity of which is shielded by the bioinert catecholic hPGs. Mono-catecholic hPGs finally terminate all of the free catechols to build a flexible bioinert top layer. These coatings perfectly prevent protein and cell adhesion.