title: Nitro-Group Functionalization of Dopamine and its Contribution to the Viscoelastic Properties of Catechol-Containing Nanocomposite Hydrogels.
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.
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931, USA.
authors.forename: Xiaochu
authors.initials: X
authors.lastname: Ding
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931, USA.
authors.forename: Giri K
authors.initials: GK
authors.lastname: Vegesna
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Meng
authors.affiliation: Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931, USA.
authors.forename: Bruce P
authors.initials: BP
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Michigan Technological University, Houghton, MI 49931, USA.
authors.forename: Audra
authors.initials: A
authors.lastname: Winter
keywords: catechol; hydrogels; interfacial binding; nanocomposites; nitro-group functionalization