The oligomeric A2 plus monomeric B3 synthetic methodology provided highly branched, poly(ether urethane)s based on IMP (B 3) and isocyanate endcapped polyethers. 13C 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 13C NMR resolution in spectra for branched polyurethanes. The 13C 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 83 monomer for branching; however, an equation that incorporated the linear contribution of the A2 oligomer provided a more accurate DB for highly branched polyurethanes.
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