Grafting of N‐vinylpyrrolidone onto segmented polyurethane initiated by 2,2′‐azoisobutyronitrile

An unsaturated segmented polyurethane was prepared from cis‐2‐butene‐1,4‐diol, poly(ethylene glycol), butane‐1,4‐diol, and methylene bis(4‐phenyl isocyanate). Graft copolymerization of N‐vinylpyrrolidone onto the segmented polyurethane was studied using 2,2′‐azoisobutyronitrile (AIBN) as initiator in DMF as solvent. The graft copolymers were isolated from the homopolymer and the ungrafted polyurethane by selective solvent extraction. The effect of reaction time, temperature, and of monomer and initiator concentrations on the degree of grafting was also investigated. The percent grafting was enhanced with increasing [AIBN] up to 40 mmol.dm‐3, but then decreased at higher concentrations. An explanation based on complex formation between the monomer and the urethane linkages in polyurethane is suggested.