In situ synthesis of a microbial fouling resistant, nanofibrillar cellulose-hyperbranched epoxy composite for advanced coating applications

High performance polymeric materials have a wide variety of applications right from household smart paints and coatings to biomedical devices. This study reports a novel in situ synthesis of a hyperbranched epoxy nanocomposite (HENC). Nanofibrillar cellulose (NFC) was modified with a branch generating moiety, triethanol amine (MNFC) and simultaneously embedded with silver nanoparticles. This MNFC was utilized as a core to synthesize HENC via an in situ approach by reacting with bisphenol A and epichlorohydrin. The chemical structure of HENC was confirmed by FTIR, 1H and 13C NMR studies, with degree of branching 0.83. The poly(amido amine) cured HENC thermosets exhibited very high tensile strength (up to 160.34 MPa), without compromising the elongation at break (25.7%). Further, excellent wood to wood substrate adhesion (∼2423 MPa) was provided by the HENC. Inherent antimicrobial activity of silver nanoparticles was conferred onto HENC, as evident from the assays against Staphylococcus aureus (minimum inhibition concentration, MIC ∼120 μg/mL) and Candida albicans (MIC ∼132 μg/mL). The HENC system thus renders a microbial fouling resistant, mechanically strong coating material with excellent adhesive power. The most fascinating part of the investigation is the synthetic protocol, which is devoid of tedious solution or melt-mixing methods to generate nanocomposite.