AB type polyaddition route to thermoplastic polyurethanes from fatty acid derivatives

Abstract

Naturally occurring oleic acid and undecylenic acid derivatives were successfully utilized to synthesize a series of new semi-crystalline polyurethanes via the AB-type polycondensation approach. A set of four novel AB-type monomers was prepared via the use of environmentally benign thiol–ene chemistry. These AB-type monomers were self-polycondensed (with or without catalyst) in two ways: (a) the hydroxyl–acyl azide approach and (b) the melt transurethane method in order to obtain reasonably high molar mass polyurethanes. The resulting polymers were thoroughly characterized by NMR, SEC, DSC, TGA and MALDI-TOF mass spectroscopy. The MALDI-TOF analysis confirmed the formation of linear polyurethanes with a trace amount of macrocycles. All the polyurethanes exhibited fair thermal stability with no significant weight loss below 200 °C. The polyurethanes based on undecylenic acid as a monomer displayed a thermoplastic behavior with well-identified melting transitions. Further, DSC analysis revealed that polyurethanes prepared from undecylenic acid by different methods showed different glass and melting transitions. Two glass transition temperatures due to soft and hard segments were observed for polyurethanes synthesized from oleic acid derivatives, indicating a phase-separated morphology.