Synthesis of 1,2,3-triazole group-containing isomannide-based aromatic new polyurethanes

Abstract

Ten new carbohydrate-based aromatic polyurethanes have been synthesized using isomannide and/or a new 1,2,3-triazole isomannide derivative, IV, as the diol source in the polymerization reactions. As the isocyanate source, 1,4-phenylene diisocyanate or 2,4-toluene diisocyanate was used. To synthesize compound IV, isomannide was tosylated, the tosyl groups were substituted with azide, the triazole ring was formed by reaction with 2,4-pentane dione and finally carbonyl groups were converted into oximes. The synthesis of copolymers and terpolymers was performed using different proportions of diisocyanate and diol sources in DMF. The structural elucidation of the synthesized compounds and polymers was performed using spectroscopic techniques such as FTIR, 1D- and 2D-NMR and HRMS. The thermal behaviour and molecular weight distribution of polymers were analyzed by thermal gravimetric analysis and gel permeation chromatography, respectively. The surface properties of the polymers were analyzed using scanning electron microscopy. A comparative study on thermal behaviour of the synthesized polymers showed that polymers containing a higher amount of compound IV displayed better thermal stability. The average molecular weights of copolymers were observed to vary from 7,900 (PUR-3) to 21,000 (PUR-4) whereas for terpolymers, values of 19,000 (PUR-5), 5,100 (PUR-6), 22,000 (PUR-8) and 28,000 (PUR-9) were found. The diisocyanate source was found to have more effect on the surface properties of polymers than the diol source: when 2,4-toluene diisocyanate was used in polymer synthesis, the resultant polymers had a spongy morphology with cavities while a polymer matrix containing spheres and platelets was obtained when 1,4-toluene diisocyanate was used.