I have tried it with MDI,TDI,IPDI,HDI and Polyols like PEG,PPG,PCL with 1000 & 2000 g/mol molecular weight & DBTDL as a catalyst.

I have use solvents like Acetone, DMF & THF.

Whole experiment performed under nitrogen environment and polyols were dried in vacuum oven overnight.

but after complete addition of diisocyanate drop wise into reaction mixture i found that gel formation occurs but my aim is to form isocyanate terminated prepolymer.