Poly[N‐isopropyl acrylamide]‐co‐polyurethane copolymers for controlled release of urea

A novel block copolymer of poly[ N ‐isopropyl acrylamide]‐ co ‐polyurethane was designed, synthesized, and applied as controlled release fertilizer coating. Structural confirmation of the copolymer was performed using FTIR and 1 H‐NMR spectra and elemental analysis. The coating process consists essentially of immersing urea granules in molten polymer and removing the coated urea from the melt by centrifugal action. The morphology of the coated urea was studied using scanning electron microscope (SEM). The polymer coat of the urea granules was found to swell in water forming pores and enabling the release of urea. The urea released from the granule, monitored using a mass spectroscopy technique, was found to be governed by pH of the aqueous medium. The study anticipates development of a beneficiary fertilizer coat in terms of improving controlled release over a period of time which can be tailored by soil temperature, pH and moisture.