Sybrand van der Zwaag

A translation of the structure of mussel byssal threads into synthetic materials by the utilization of histidine-rich block copolymers

Mussel byssal threads are well-known due to their self-healing ability after the mechanical stress caused by waves. The proposed mechanism demonstrates the importance of reversible histidine–metal interactions as well as the block copolymer-like hierarchical architecture of the underlying protein structure. Taking these two aspects as inspiration for the design of synthetic analogs, different histidine-rich block copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. The hard domain was mimicked using polystyrene and the soft domain consists of n-butyl acrylate (BA) as well as histidine moieties as ligands. The block copolymers were crosslinked using different zinc(II) salts and the resulting metallopolymers were investigated with respect to their self-healing abilities. The observed two-step mechanism of the self-healing process was studied in detail. Furthermore, the mechanical properties were determined by nanoindentation and were correlated with other results.

Predicting the cooperative effect of Mn–Si and Mn–Mo on the incomplete bainite formation in quaternary Fe–C alloys

ABSTRACT Predicting the effect of alloying elements on the degree of incomplete austenite to bainite transformation in low carbon steels is of great industrial importance. This study introduces an extended Gibbs energy balance model which makes use of an additive approach to calculate the coupled effect of Mn, Si and Mo on the fraction of bainitic ferrite after the incomplete transformation in multicomponent steels. The model predicts significant effects of Mn and Mo and the negligible effect of Si levels on the fraction of bainitic ferrite. This is attributed to the high value of dissipation of Gibbs energy caused by interfacial diffusion of Mn and Mo and low values caused by Si diffusion. The model predictions for quaternary Fe–C–Mn–Si system are comparable with the experimentally measured values of bainite fraction. For the Fe–C–Mn–Mo system, the agreement is less accurate and the accuracy decreases with increasing Mo content, which is attributed a substantial carbide formation but interaction effects between Mn and Mo or a temperature dependent binding energy cannot be ruled out.