SYNTHESIS AND CHARACTERIZATION OF HYPERBRANCHED POLYURETHANES PREPARED FROM BLOCKED ISOCYANATE MONOMERS BY STEP-GROWTH POLYMERIZATION

The step-growth polymerization of the AB2 blocked isocyanate monomr 3,5-bis((benzoxycarbonyl)imino)benzyl alcohol at a monomer concentration of 1 M results in the formation of a hyperbranched polyurethane with M(W) = 34 000. When the monomer concentration is increased to 2 M, a cross-linked polymer forms through the occurrence of a small amount of side reactions involving free isocyanate intermediates. Soluble polymers can be prepared, independent of the monomer concentration, when an end-capping alcohol is added at the start of the polymerization. The end-capping groups change the physical properties of the polymers such as T(g) and solubility.