Effect of Solvent Interactions on the Properties of Polyurethane Films

A series of segmented polyurethanes were synthesized by the reaction of poly (ethyleneadypate) diol, 4,4’-methylene-bis(phenyl isocyanate) and ethylene glycol. Various solvents were used as reaction media: N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) and mixtures of NMP with DMF, toluene, and ethyl acetate (at a rate 80/20 weight). These polyurethanes exhibited different behaviors due to different interactions between solvents and macromolecular chains or solvents and water. These phenomena in combination with the phase segregation in polyurethanes arising from the incompatibility between the hard and soft segments were utilized to produce a variety of polyurethane membranes by immersion precipitation. The type of solvent has a strong effect on the properties and morphology of polymers when they are cast using different solvents, which was confirmed by thermal and mechanical measurements.