Modular Synthesis and Patterning of High-Stiffness Networks by Postpolymerization Functionalization with Iron–Catechol Complexes
Declan P. Shannon, Joshua D. Moon, Christopher W. Barney, Nairiti J. Sinha, Kai-Chieh Yang, Seamus D. Jones, Ronnie V. Garcia, Matthew E. Helgeson, Rachel A. Segalman, Megan T. Valentine, Craig J. Hawker
Abstract
High Resolution Image Download MS PowerPoint Slide Bioinspired iron–catechol cross-links have shown remarkable success in increasing the mechanical properties of polymer networks, in part due to clustering of Fe 3+ –catechol domains which act as secondary network reinforcing sites. We report a versatile synthetic procedure to prepare modular PEG-acrylate networks with independently tunable covalent bis(acrylate) and supramolecular Fe 3+ –catechol cross-linking. Initial control of network structure is achieved through radical polymerization and cross-linking, followed by postpolymerization incorporation of catechol units via quantitative active ester chemistry and subsequent complexation with iron salts. By tuning the ratio of each building block, dual cross-linked networks reinforced by clustered iron–catechol domains are prepared and exhibit a wide range of properties (Young’s moduli up to ∼245 MPa), well beyond the values achieved through purely covalent cross-linking. This stepwise approach to mixed covalent and metal–ligand cross-linked networks also permits local patterning of PEG-based films through masking techniques forming distinct hard, soft, and gradient regions.