Segmented poly(urethane-urea)s synthesized directly from isocyanate-terminated prepolymers and masked diamines I. Quantitative synthesis

Abstract

An attempt was made for quantitative synthesis of segmented poly(urethane urea)s (PUUs), not via solution state, but directly from an isocyanate-terminated prepolymer prepared from an excess molar concentration of 4,4′-methylenediphenyldiisocyanate with poly(tetramethylencoxide) (M̄n = 2010) and reaction products from acetone and ethylenediamine (EDA) consisting of N-isopropylideneelhylcnediamine (1), N,N′-diisopropylidencethylenediamine (2), 2,2-dimethylimidazolidine (3) as main product, water, and the unreacted raw materials. With increasing the masking ratio of acetone to EDA, the concentrations of the ketimine groups and water increase while those of the imidazolidine and EDA generally decrease, the molar fraction of the by-product from the reaction of an isocyanate group with water was increased mainly because of the catalytic effect of the ketimine groups. Acetic acid played the significant roll to eliminate the side reaction by accelerating disappearance rate of (1) ((2)) and the quantitative yield of PUU was attained at 40°C when the acid concentration and the masking ratio were 3.50 × 10-3 mol kg-1 and 1.4, respectively.