Nitrogen rich hyperbranched polyol via A₃ + B₃ polycondensation: thermal, mechanical, anti-corrosive and antimicrobial properties of poly (urethane-urea)

High performance, high solid and low in volatile organic content (VOC) multifunctional coatings have wide applications in protection and decoration of materials. This work describes the synthesis of novel hyperbranched polymer (HBP) based polyurethanes (PUs) that exhibit antimicrobial property and are environmentally benign. Nitrogen rich HBP having nitrogen atom as a core was synthesized by A₃ + B₃ polycondensation in two step reaction. In the first step, monomer A₃, a tricarboxylic acid, was synthesized by triethanolamine (B_3, the core) with succinic anhydride, while in the second step, monomers A₃ and B₃ were used to synthesize hyperbranched polyester polyol by polycondensation reaction. The HBP thus formed was reacted with 4,4′-methylenedicyclohexyl diisocyanate (H¹² MDI) in varying ratios of NCO to OH to form NCO- terminated PU prepolymers in a self-catalyzed reaction. The prepolymers were then coated onto mild steel panels as well as tin foils and stored at ambient conditions for 20 days to evaluate the moisture-cured PU-urea film properties. The formation of tribasic acid (A₃), HBP and PU was confirmed by ¹H NMR, ¹³C NMR, FTIR and ESI-mass spectroscopy. Thermal, mechanical, anti-corrosive and antimicrobial studies as well as the effect of varying NCO to OH ratio on these properties were investigated. The properties of PU-urea were found to be suitable for corrosion protection as well as biomedical and various other applications.