Degree of Branching of Highly Branched Polyurethanes Synthesized via the Oligomeric A2 Plus B3 Methodology

The oligomeric A 2 plus monomeric B 3 synthetic methodology provided highly branched, poly(ether urethane)s based on TMP (B 3 ) and isocyanate endcapped polyethers. 13 C NMR spectroscopic assignments for the branched polyurethanes were verified using model urethane-containing compounds based on TMP and a monofunctional isocyanate (either cyclohexyl or phenyl isocyanate (PI)). Derivatization of hydroxyl endgroups with trifluoroacetic anhydride enhanced the 13 C NMR resolution in spectra for branched polyurethanes. The 13 C NMR resonance for the linear unit exhibited a broad shoulder due to quaternary carbons that were attributed to cyclic species in the highly branched polyurethanes. The classical DB calculation revealed the efficiency of the B 3 monomer for branching; however, an equation that incorporated the linear contribution of the A 2 oligomer provided a more accurate DB for highly branched polyurethanes.