The synthesis of poly(arylthiols) and their utilization in the preparation of cross-linked dynamic covalent polymer nanoparticles and hydrogels

Abstract

Dynamic covalent bonds can be utilized to endow polymer-based structures, such as nanoparticles or hydrogel networks, with the abilities to adapt their structures or compositions in response to an external stimuli. In this work we investigate the potential of aromatic thiols, which because they exhibit vastly different reactivities, pK_a's and nucleophilicities in comparison to aliphatic thiols, present an alternative reversible thiol/disulfide system for utilization within polymer-based structures. We demonstrate that water-soluble arylthiol pendant-functional random copolymers capable of forming dynamic disulfide bonds can be prepared and show how they can be cross-linked into polymeric nanoparticles and hydrogel networks through the formation of disulfide cross-links which can then be cleaved to reafford the initial aromatic thiol-functionalized polymers. We highlight how careful control of reaction conditions is required to drive the self-assembly of these polymers into nanoparticles in a process which is predominately under kinetic control. The potential of these arylthiol appended polymers to be utilized within a more complex orthogonal dynamic covalent polymer system also featuring polymer chains cross-linked through reversible imine bond formation was also investigated. This work expands the utility of aromatic disulfides in dynamic polymer systems and will broaden the range and versatility of dynamic covalent disulfide-based materials available to researchers in the fields of nanochemistry and functional materials.