Polyhydroxyurethanes (PHUs) Derived from Diphenolic Acid and Carbon Dioxide and Their Application in Solvent- and Water-Borne PHU Coatings

To develop biobased polyurethanes (PUs) via a less hazardous, nonisocyanate route, herein we synthesize a series of biobased polyhydroxyurethanes (PHUs) by reacting a new biobased cyclocarbonate (derived from renewable diphenolic acid and carbon dioxide) with ethylenediamine (EDA), diethylenetriamine (DETA), and isophoronediamine (IPDA), corresponding to PHU-EDA, PHU-DETA, and PHU-IPDA, respectively. Their molecular structures are identified from 1H NMR and FTIR analyses. Gel permeation chromatography (GPC) analysis shows that the molecular weights of these PHUs grow to as high as 5 kDa in a short reaction time (4 h) at a relatively low reaction temperature (80 degrees C). Subsequently, the solvent-borne (in acetone) coatings of these PHUs are successfully fabricated with diglycidyl ether of bisphenol A as the cross-linker. The cured PHU coatings on aluminum panels show the high pencil hardness (up to 4 H), adhesive force (up to grade 1), glass transition as high as 116 degrees C, and initial thermal degradation temperature up to 190 degrees C. Furthermore, we realize the good dispersion of these PHUs in water by introducing chemically bonded carboxylic anions into the molecular backbone to form a stable aqueous emulsion with well-controlled particle sizes and further demonstrate its application in a water-borne PHU coating with good mechanical and thermal properties. Overall, we develop a facile yet effective method to prepare sustainable, biobased PHUs based on diphenolic acid and carbon dioxide via a safer, greener nonisocyanate route and furthermore demonstrated their use as solvent-borne coatings and greener water-borne coatings of reduced environmental impact.