Investigations on non isocyanate polyurethanes

Abstract

Polyurethanes are versatile polymers finding applications as cushions, beds, bio-medical newlinedevices and high-tech aerospace materials. Several tonnes of polyurethanes are being newlineconsumed every year. They are usually produced by the reaction between isocyanates newlineand polyols. However, the isocyanate monomers are now classified within a carcinogenic newlinegroup. They are highly hygroscopic; the free isocyanate group may react with moisture newlineto form urea, amine and CO2, leading to the deterioration of the mechanical strength of newlinethe PU being derived. newlineRecently, development of polyurethanes through non-isocyanate routes [poly(hydroxy newlineurethane)s; PHUs] has emerged as a potential area of research. The PHUs can be newlinesynthesized by different routes which include: i) trans-urethinisation between a newlinebicarbamate and a diol ii) aziridine co-polymerisation with CO2 and iii) ring opening newlinepolyaddition between a bicyclic carbonate and a diamine. Among these methods, the newlinemost employed one is the latter, as it is highly economical, from the industrial point of newlineview and offers a green aspect. newlineThe initial synthesis of bicyclic carbonates from a bisepoxy and CO2 is also considered newlineas an important strategy as it would assist for the chemical fixation of CO2. Avoiding newlineisocyanate chemistry and employing CO2 gas in a chemical transformation route to obtain newlinePHUs are useful and interesting approaches. The main objective of this work is to newlineinvestigate the synthesis of novel polyurethanes through non-isocyanate routes. newlineThe first chapter of the thesis presents an introduction to polyurethane chemistry and newlinerecent developments related to it. The second chapter gives an account of the analytical newlineprocedures followed for the investigation. The third chapter contains the results in connection with the synthesis of a cyclic newlinecarbonate functional monomer through an oxirane-CO2 reaction. newline