Method of making a diisocyanate terminated macromer

A method for making a polyisocyanate macromer of the formula:

• wherein f is two or more;
• “a” is zero to five;
• and when “a” is one to five, R1 is
• where the ethylene oxide portion of R1 may be linear or branched, and c may range from 1 to 100;
• R2 is
• where R3 is a linear or branched residue of a water soluble polymer that is capable of forming ester linkages to R4, and (i) ester linkages together with the carbonyl group of the benzoyl isocyanate moiety when “a” is zero, or (ii) urethane linkages to R1 when “a” is one or more;
• and R4 is an organic residue capable of having carboxylate end-groups;
• comprising the steps of:
• (a) condensing a linear polyalkylene glycol with a polycarboxylic acid so that the polycarboxylic acid is terminated with hydroxyl groups from the polyalkylene glycol, to form a polyethylene glycol ester polyol;
• (b) synthesizing an aromatic dinitro intermediate;
• (c) hydrogenating the aromatic dinitro intermediate to form a diamine intermediate,
• (d) purifying the diamine intermediate;
• (e) phosgenating the diamine intermediate to form a diisocyanate intermediate by reacting the diamine intermediate with triphosgene in a solvent;
• and
• (f) reacting the diisocyanate intermediate with the polyethylene glycol ester polyol to form an isocyonate terminated polyethylene glycol ester urethane.