Preparation of Isophorone Diisocyanate Terminated Star Polyethers

Reactive star shaped isocyanate prepolymers have been prepared by endcapping hydroxy functionalized poly(alkylene oxide)s with isophorone diisocyanate. Selective reaction conditions have been worked out to reduce the amount of chain extension and crosslinking due to reaction of both isocyanate groups of the IPDI moieties. By combining 1H and 13C NMR spectroscopy with size exclusion chromatography (SEC), the fractions of the monourethane isomers, and the extent of diurethane formation was determined. The effect of catalysis, of the excess of isocyanate, and of the type of poly(alkylene oxide) on the product structure and composition were investigated.