SOLID STATE NMR STUDY OF IMMOBILIZED POLYMERS

Polymers containing catechol functional groups, inspired by marine mussel adhesive proteins, have attracted significant interest for their potential applications as bio-inspired adhesives and composite materials. In this study, the structural interactions between poly(N-catechol dimethyl acrylamide) (PDMAA) and fumed silica (SiO₂) were investigated using solid-state nuclear magnetic resonance (NMR) spectroscopy to determine the nature of their bonding interactions. Solid-state NMR techniques, including 13C CP-MAS, 29Si MAS, and 29Si CP-MAS, were employed to analyze PDMAA-SiO₂ composites synthesized under acidic, neutral, and basic conditions. The 13C CP-MAS spectra confirmed the presence of PDMAA within the composites, identifying characteristic chemical shifts corresponding to key functional groups, while the 29Si MAS and 29Si CP-MAS spectra showed no significant shifts or new peaks indicative of covalent bond formation. The Q2, Q3, and Q4 silicon environments presented by the presence of similar peaks throughout all studied samples. Tn groups indicating -Si-R signals were not observed, suggesting the absence of covalent bond formation between silica and the polymer. These results indicate that the interaction between PDMAA and SiO₂ is non-covalent, likely mediated through hydrogen bonding, providing insights into the structural characteristics of PDMAA-SiO₂ composites for adhesive material development.