Synthesis and characterization of novel hydroxyl-terminated hyperbranched polyurethanes

Abstract A series of novel hydroxyl-terminated hyperbranched polyurethanes (HBPUs) were synthesized via stepwise polymerization by diethanolamine (DEOA), isophorone diisocyanate (IPDI) and trimethylolpropane (TMP). It is interesting to note that the HBPUs can be purified by water. The HBPUs were characterized with 1 H nuclear magnetic resonance (NMR), 13 C NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The average degree of branching (DB) of HBPUs was calculated from the first generation to the fourth generation to be 1.00, 0.74, 0.59 and 0.57 by quantitative 13 C NMR, respectively. The branching model and molecular structure of HBPUs were deduced by the 13 C NMR and the value of DB. To investigate the changes of hydrogen bonding interaction in HBPUs with a variation in structure of different generations, the deconvolution of FT-IR spectra was carried out using Origin 7.0 software through the Gaussian curve-fitting method. The ratio of hydrogen-bonded -NH and -OH groups of HBPUs was calculated to be 80.8%, 85.1%, 84.8% and 85.4% from the first generation to the fourth generation by deconvoluted -NH and -OH zone, respectively. The interaction of hydrogen bonding and glass transition temperature (Tg) of HBPUs increased with the increase of generation. The trend of thermal stability and Tg coincide with the change of hydrogen-bonded interactions.