Phosphate functionalized nonisocyanate polyurethanes with bio-origin, water solubility and biodegradability

Abstract

Nonisocyanate polyurethanes (NIPUs) are an emerging class of polyurethanes produced by circumventing the use of hazardous isocyanates and phosgene in their synthetic routes. In this study, we introduce a novel class of water-soluble/dispersible nonisocyanate polyurethanes (NIPUs) containing phosphate pendant groups, referred to as NIPU phosphate monoesters, by applying green chemistry principles. Linear NIPU polymers with number average molecular weight (M_n) values ranging between 7400 and 13 600 Da and weight average molecular weight (M_w) values between 13 900 and 27 800 Da were synthesised by the polymerization of bio-derived cyclic biscarbonates 4,4′-(((furan-2,5-diylbis(methylene)) bis(oxy))bis(methylene)) bis(1,3-dioxolan-2-one) (FuBCC) and bis((2-oxo-1,3-dioxolan-4-yl)methyl) succinate (SuBCC) with 1,5-pentanediamine (cadaverine) by utilizing green solvents. Subsequent functionalization of the resultant NIPUs via mild and selective phosphorylation using tetrabutylammonium dihydrogenphosphate (TBAP) as a phosphate source delivered NIPU phosphate monoesters containing up to 50% phosphate functionality as determined by ¹H NMR. Interestingly, these phosphate-containing NIPUs were soluble/dispersible in water without the need for any external surfactants/co-solvents and demonstrated inherent aerobic biodegradability (56–75% in 28 days). Furthermore, the NIPU phosphate monoesters exhibited remarkable biocompatibility, showing slight to no growth inhibition of human keratinocyte HaCaT cells at concentrations up to 1 mg mL⁻¹. In vitro skin irritation assays on reconstructed human epidermis confirmed their non-skin irritant properties. These NIPU phosphate monoesters also exhibited multifunctional characteristics including oil-in-water emulsion stabilization ability and antimicrobial activity. This work emphasizes the scope and potential of these bio-derived, non-toxic and biodegradable nonisocyanate polyurethane phosphate monoesters as multifunctional additives in personal care/cosmetic applications.