Influence of patch size and chemistry on the catalytic activity of patchy hybrid nonwovens

Abstract

In this work, we provide a detailed study on the influence of patch size and chemistry on the catalytic activity of patchy hybrid nonwovens in the gold nanoparticle (Au NP) catalysed alcoholysis of dimethylphenylsilane in <i>n</i>-butanol. The nonwovens were produced by coaxial electrospinning, employing a polystyrene solution as the core and a dispersion of spherical or worm-like patchy micelles with functional, amino group-bearing patches (dimethyl and diisopropyl amino groups as anchor groups for Au NP) as the shell. Subsequent loading by dipping into a dispersion of preformed Au NPs yields the patchy hybrid nonwovens. In terms of NP stabilization, <i>i.e.</i>, preventing agglomeration, worm-like micelles with poly(<i>N</i>,<i>N</i>-dimethylaminoethyl methacrylamide) (PDMA) patches are most efficient. Kinetic studies employing an extended 1^st order kinetics model, which includes the observed induction periods, revealed a strong dependence on the accessibility of the Au NPs' surface to the reactants. The accessibility is controlled by the swellability of the functional patches in <i>n</i>-butanol, which depends on both patch chemistry and size. As a result, significantly longer induction (<i>t</i> _ind) and reaction (<i>t</i> _R) times were observed for the 1^st catalysis cycles in comparison to the 10^th cycles and nonwovens with more polar PDMA patches show a significantly lower <i>t</i> _R in the 1^st catalysis cycle. Thus, the unique patchy surface structure allows tailoring the properties of this "<i>tea-bag</i>"-like catalyst system in terms of NP stabilization and catalytic performance, which resulted in a significant reduction of <i>t</i> _R to about 4 h for an optimized system.