SYNTHESIS AND CHARACTERIZATION OF HYPERBRANCHED POLYURETHANE-BENZYLTETRAZOLE

A series of hyperbranched polyurethane-benzyltetrazoles (H-PBTZs) with different linkage structures were synthesized via the polycondensation of hexamethylenediisocyanate as an A(2) type monomer with (4-(1H-tetrazol-5-yl) benzyl)-diethanolamine (TBDEA) as a BB'(2) type monomer in the absence of catalyst at different temperatures. The FTIR, and C-13 and H-1-NMR spectroscopy were used to characterize the molecular structures of TBDEA and H-PBTZs as well as the counterpart linear polyurethane-benzyltetrazole (L-PBTZ). The molecular composition was determined by the reaction selectivity that the isocyanate group reacted with the hydroxyl group in diethanolamine segment or the active hydrogen atom on tetrazole ring. Raising reaction temperature was propitious to the reaction of isocyanate group with the active hydrogen atom on tetrazole ring. The degrees of branching (DB) for H-PBTZs obtained from the H-1-NMR spectra increased with raising reaction temperature. The wider molecular weight distribution of 1.7-2.9 for H-PBTZs was obtained via GPC analysis. TGA results showed that H-PBTZs had high thermal stability compared with L-PBTZ.