Abstract
Hexamethylenediamine (HMDA) and other long chain aliphatic diamines can induce substrate-independent polymer film deposition from dopamine and several other catechols substrates at relatively low concentrations, however the mechanism of the diamine-promoted effect has remained little understood. Herein, we report data indicating that: (a) film deposition from 1 mM HMDA and dopamine is not affected by chemical oxidation with periodate but is markedly inhibited by resorcinol, which also prevents PDA film formation at 10 mM monomer concentration in the absence of HMDA; (b) N-acetylation of HMDA completely inhibits the effect on PDA film formation; (c) HMDA enables surface functionalization with 1 mM 5,6-dihydroxyindole (DHI) polymerization at pH 9.0 in a resorcinol-inhibitable manner. Structural investigation of the polymers produced from dopamine and DHI in the presence of HMDA using solid state 13C and 15N NMR and MALDI-MS suggested formation of covalent cross linked structures. It is concluded that HMDA enhances polydopamine adhesion by acting both on dopamine quinone and downstream, e.g., via covalent coupling with DHI. These results provide new insights into the mechanisms of PDA adhesion and disclose resorcinol as a new potent tool for targeting/mapping quinone intermediates and for controlling polymer growth.
Highlights
The substrate and material-independent adhesion and deposition of catechol-based thin films and coatings under wet conditions is a topic of growing interest in materials science for a broad range of technological and biomedical applications (Suárez-García et al, 2017; d’Ischia and Ruiz-Molina, 2018)
A most relevant finding was that hexamethylenediamine (HMDA) and other long chain aliphaticamines enable deposition of PDA films under low dopamine concentration conditions (
A marked, though not complete, inhibition of film deposition was again observed, suggesting coupling of resorcinol with quinone intermediates involved in adhesion and cross-linking (Figure 4). Overall these results provide evidence that resorcinol can target dopamine quinone hindering adhesion-producing coupling with HMDA, but do not allow to settle a critical issue relating to the actual role of dopamine quinone in the adhesion process, i.e.,: is the quinone the main structural determinant of adhesion, being directly involved in coupling with amine-containing chains, or is it the precursor of the species serving as the actual target for the amine groups involved in adhesion and cohesion?
Summary
The substrate and material-independent adhesion and deposition of catechol-based thin films and coatings under wet conditions is a topic of growing interest in materials science for a broad range of technological and biomedical applications (Suárez-García et al, 2017; d’Ischia and Ruiz-Molina, 2018). A most relevant finding was that hexamethylenediamine (HMDA) and other long chain aliphatic (di)amines enable deposition of PDA films under low dopamine concentration conditions (
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
