Environment-friendly synthesis of sustainable chitosan-based nonisocyanate polyurethane: A biobased polymeric film

Sustainable, biobased nonisocyanate polyurethane (NIPU) films having excellent water absorption characteristics were synthesized by a green-chemistry approach, eliminating the use of any toxic component. An environment-friendly bulk polyaddition reaction was carried out between a natural amine-containing polysaccharide, chitosan, and carbonated soybean oil (CSBO) to prepare the NIPUs. Epoxidized soybean oil was reacted with carbon dioxide to obtain CSBO and the conversion was confirmed by Fourier transform infra-red and H-1 nuclear magnetic resonance spectroscopies. NIPUs synthesized via this method did not involve the use of any curing agent and the crosslinking density of the polymer could be varied by altering the amine content. NIPUs with higher chitosan content showed better thermal and chemical properties, and superior water absorption characteristics. FTIR studies confirmed the typical linkages of polyurethane and the swelling behavior justified its enhanced resistance to organic solvents. Karl Fischer titration study proved the excellent water-absorption capacity by absorbing similar to 90% moisture from toluene. These properties enable NIPUs to have diverse probable applications in the fields of chemical-resistant coating, sealant, and also as an inorganic plant growth substrate because of its high water holding capacity.