Bernd Reck

The underlying mechanisms for self-healing of poly(disulfide)s.

Recently, self-healing polymers based on disulfide compounds have gained attention due to the versatile chemistry of disulfide bonds and easy implementation into polymeric materials. However, the underlying mechanisms of disulfide exchange which induce the self-healing effect in poly(disulfide)s remain unclear. In this work, we elucidate the process of disulfide exchange using a variety of spectroscopic techniques. Comparing a model exchange reaction of 4-aminophenyl disulfide and diphenyl disulfide with modified reactions in the presence of additional radical traps or radical sources confirmed that the exchange reaction between disulfide compounds occurred via a radical-mediated mechanism. Furthermore, when investigating the effect of catalysts on the model exchange reaction, it could be concluded that catalysts enhance the disulfide exchange reaction through the formation of S-based anions in addition to the radical-mediated mechanism.

Phase Separation Driven On-Demand Debondable Waterborne Pressure-Sensitive Adhesives

A waterborne pressure-sensitive adhesive (PSA) that shows high adhesive performance and easy debondability on demand without leaving residues on the substrate (adhesive failure) has been developed. A key component of the PSA is a semicrystalline phase that is beneficial for the adhesive properties and that becomes fluid when heated above the melting temperature. Migration of this liquid-like polymer to the substrate-adhesive interface and hardening upon cooling results in a hard non-tacky interface that facilitates debonding. The effect of the particle morphology on the debonding ability is discussed.