A thioglycerol route to bio-based bis-cyclic carbonates: poly(hydroxyurethane) preparation and post-functionalization†
The present work is dedicated to the design of novel sulfur-substituted cyclic carbonates from thioglycerol, fatty acids and sugar derivatives. In this methodology, a sulfur atom is inserted in the β position of 5-membered ring cyclic carbonates via a two-step synthesis including the thiol–ene coupling of thioglycerol on fatty acid derivatives, followed by a transcarbonation. A similar strategy was adopted to prepare glycolipid-based cyclic carbonates in order to bring biodegradability to the final poly(hydroxyurethane)s. The so-formed monomers were characterized by NMR spectroscopies, HPLC and DSC. The enhanced reactivity of sulfur-substituted cyclic carbonates was demonstrated through a 1H NMR spectroscopy kinetic study of a model reaction with hexylamine. Fatty acid- and glycolipid-based sulfur-substituted bis-cyclic carbonates were then polymerized with diamines in a solvent using a catalyst-free process. FTIR, NMR, SEC, DSC and TGA were performed to investigate the PHUs’ chemical structure, molar masses and thermal properties. Finally, the so-formed PHUs were post-functionalized by sulfonation with m-CPBA taking advantage of thioether functions. The impact of the chemical modification was mostly studied on the polymer solubility and thermal stability.