1. Department of Biomedical Engineering, Michigan Technological University, Houghton, MI, USA;2. Department of Chemistry, Michigan Technological University, Houghton, MI, USA
Abstract:
Linear polyacrylamide (PAAm) is modified with dopamine or nitrodopamine (PAAm‐D and PAAm‐ND, respectively) to evaluate the effect of nitro‐group modification on the interfacial binding properties of polymer‐bound catechol. Nanocomposite hydrogels are prepared by mixing PAAm‐based polymers with Laponite and the viscoelastic properties of these materials are determined using oscillatory rheometry. The incorporation of a small amount of catechol (≈0.1 wt% in swollen hydrogel) drastically increases the shear moduli by 1–2 orders of magnitude over those of the catechol‐free control. Additionally, PAAm‐ND exhibits higher shear moduli values than PAAm‐D across the whole pH range tested (pH 3.0–9.0). Based on the calculated effective crosslinking density, effective functionality, and molecular weight between crosslinks, nitro‐group functionalization of dopamine results in a polymer network with increased crosslinking density and crosslinking points with higher functionality. Nitro‐functionalization enhances the interfacial binding property of dopamine and increases its resistant to oxidation, which results in nanocomposite hydrogels with enhanced stiffness and a viscous dissipation property.
