Wettability and surface free energy of NIPU coatings based on bis(2,3-dihydroxypropyl)ether dicarbonate

Non-isocyanate poly(hydroxyurethanes) (NIPUs) are a new class of polymers prepared without using toxic and harmful phosgene and isocyanates. The formation of NIPUs based on an environmentally friendly method from cyclic carbonates and amines is an alternative to the chemistry of conventional polyurethanes. For the first time, the surface free energy of NIPUs coatings is widely presented in the literature. In this work, we present selected properties of NIPUs coatings based on bis(2,3-dihydroxypropyl)ether dicarbonate obtained from a commercially available diglycerol and various amines. The surface free energy and its dispersion and polar components were calculated using various methods based on static measurements of contact angle of diiodomethane and water. Owens-Wendt, Fawkes and Wu methods were used in order to determine surface free energy. Moreover, wetting envelopes of NIPU coatings are presented. NIPUs exhibited high hydrophilicity due to the pendant hydroxyl groups in the macromolecule. Furthermore, the contact angle of water increases when the lengthening of a diamine carbon chain increases in NIPUs based on aliphatic amines. These results will provide valuable guidance for the application of NIPUs in coatings and adhesives. The results reveal that potential applications of NIPUs are significantly limited by high hydrophilicity of surface of NIPUs coatings.