Ferrocene fortified multifunctional hybrid polyurethane coatings: Synthesis, characterization and properties evaluation

Abstract

The present work delineates the development of ferrocene (Fc) fortified, multifunctional, hybrid polyurethane coating films. Initially ferrocene containing polyol (Fc-PL) was successfully synthesized with the assistance of catalyst free azide-alkyne click chemistry and each step of the synthesis was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), Ultraviolet-visible spectroscopy (UV/Vis) spectroscopy and Electrospray ionization mass (ESI-mass) spectrometry. Polyurethane coatings of varying concentrations of Fc-PL, polypropylene glycol (PPG), trimethylol propane (TMP) were prepared in such a way that to maintain Fc concentrations in 0, 5, 10, 15 weight percentages with respect to polyol mixture and mixed with polymeric diphenylmethane diisocyanate (PMDI) at a OH: NCO ratio of 1:1.05 and cured under atmospheric moisture to obtain corresponding polyurethane coatings and labeled as Fc-0, Fc-5, Fc-10, Fc-15. Successful incorporation of Fc into PU coatings was confirmed by energy-dispersive X-ray spectroscopy (EDS) analysis. Effect of ferrocene on thermal stability and thermo-mechanical properties was assessed by thermo-gravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) respectively and TGA suggests that onset decomposition temperature, 30 % weight loss temperature, 50 % weight loss temperature and weight % remaining at 500°C increased as Fc wt% increases from 0 to 15 wt%, which implies that thermal stability enhanced with increasing the ferrocene concentration. DMTA demonstrated that mechanical properties i.e., storage modulus enhanced and glass transition temperature (Tg) declined with increasing the ferrocene concentration, on account of redistribution of intermolecular hydrogen bonds and metal-polymer complex formation. Ferrocene effect on corrosion resistant property, water contact angle and anti-fungal susceptibility was studied by electrochemical polarization analysis, contact angle measurements and disk diffusion test respectively. Electrochemical polarization analysis revealed that corrosion resistant property improved as the ferrocene content increases from Fc-0 to Fc-15. Ferrocene additionally imparted hydrophobicity to synthesized PU coatings. Fc-5 PU coating sample showed better hydrophobicity than other samples i.e, Fc-0, Fc-10 and Fc-15. These PU coatings are anti-fungal in nature due to the presence of hydrogen bonded triazole ring formed by click chemistry.