Incorporating dynamic bonds into polymers enables static thermosets to be transformed into active materials, possessing the reprocessability of thermoplastics while maintaining the bulk properties of fully crosslinked networks. This new class of materials, termed covalent adaptable networks (CANs), has helped bridge the gap between traditional thermosets and thermoplastics. Here, epoxy-based adaptable networks were synthesized by combining a diepoxide monomer with an oligosiloxane prepolymer containing aminopropyl groups, which crosslink irreversibly, and silanolate end-groups, which participate in dynamic bonding. Two separate diepoxide crosslinkers were used to give a range of soft to stiff materials with a Young’s modulus varying from 12 MPa to 2.2 GPa. This study documents how the thermal and mechanical properties (e.g., glass transition temperature and modulus) are affected by compositional changes in these silanolate networks. Dynamic bonding also results in self-healing properties, offering the ability to repair structural polymers and composites. When combined with tunable mechanical properties, self-healing capabilities make these materials well-suited to be sustainable alternatives for many traditional thermosets. For example, we demonstrated the ability to weld a stiff epoxy thermoset to a dissimilar soft material, a feature traditional epoxies do not permit. Graphical abstract

Achieving adhesive bonding in wet environments remains a significant challenge in both day-to-day life and industrial applications. Inspired by how marine shellfish stick to rocks, a wide variety of innovative polymer adhesives containing catechol moieties have been developed by several research groups. Despite displaying impressive performance, these adhesives have not yet emerged on the market. Difficulties associated with translating small-scale academic research to industrial production have persisted. In this paper, we focus our attention on poly(vinylcatechol-styrene), a biomimetic polymer that has shown considerable bonding in both dry and underwater conditions. Herein, we tackled three issues to help bring this polymer beyond academic laboratories: monomer sourcing, polymerization processes, and deprotection steps. Thus, we propose a new route to produce poly(vinylcatecholstyrene) made of (i) a 3,4-dimethoxystyrene monomer preparation from 3′,4′-dimethoxyacetophenone, a low-cost and highavailability reagent, (ii) a suspension polymerization to yield the intermediate poly(3,4-dimethoxystyrene-styrene) at the large scale, and (iii) an iodocylohexane-induced methyl cleavage to obtain the final poly(vinylcatechol-styrene). In our laboratory, we could synthesize this adhesive polymer at up to 60 g scales, avoided harsh reaction conditions, and reduced the cost of the polymer by half. Cost calculations are described both for materials only and also when considering labor and energy. An unexpected bonus was improved performance in both dry and wet conditions.

Human-in-the-loop experimentation enables interactive machine learning for continuous flow chemistry reaction planning and optimization.