Sugar-Based Hydrophilic Polyurethanes and Polyureas

Novel linear homogeneous polyurethanes and polyureas with enhanced hydrophilic character have been successfully prepared from sugar-based monomers having their hydroxyl groups free or partially protected. By the reaction of primary hydroxyl groups of xylitol with dimethyl hexamethylene dicarbamate (HMDC) or di-tert-butyl-4,4'-diphenyl methyl dicarbamate (MDC), two new linear semicrystalline polyurethanes [PU(X-HMDC) and PU(X-MDC)] have been prepared. Likewise, by the reaction of xylitol with the analogous diisocyanates hexamethylene diisocyanate (HMDI) or 4,4'-methylenebis(phenyl isocyanate) (MDI), similar polyurethanes [PU(X-HMDI) and PU(X-MDI)] were obtained. However, these latter polyurethanes present some degree of crosslinking because of the higher reactivity of the diisocyanate comonomers. Linear hydrophilic polyureas having free hydroxyl groups joined to the main chain have also been prepared by the reaction of the same diisocyanates (HMDI and MDI) with 1,6-diamino-1,6-dideoxy-D-mannitol and 1,6-diamino-1,6-dideoxy-3: 4-O-isopropylidene-D-mannitol. As far as we are aware, this kind of polyhydroxylated polyurea has not been previously described in the literature. The new polymers were characterized by standard methods (elemental analyses, gel permeation chromatography, IR, and NMR). The polyurethanes were hydrolytically degradable under physiological conditions, in contrast with less-hydrophilic linear polyurethanes previously described. The thermal properties of the novel polymers were investigated by thermogravimetric analysis and differential scanning calorimetry. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1953-1961, 2011