Application of Thiol-ene "click" Chemistry to Preparation of Hyperbranched Polyurethane Acrylate Oligomers Containing Carboxyl Groups

A new type of hyperbranched polyurethane terminated by carboxyl groups (HBP-COOH) has been synthesized by thiol-ene "click" reaction. The carboxyl groups of HBP-COOH were further modified by glycidyl methacrylate at different feed ratio to produce a series of hyperbranched polyurethane acrylate oligomers containing carboxyl groups (HBPUA-COOHs). The structures of products were characterized by FT-IR, H-1-NMR spectroscopy and gel permeation chromatography (GPC). The photosensitive groups of these synthesized HBPUA-COOHs were measured with UV-Vis spectrophotometer. It was shown that the HBPUA-COOHs had sharp absorption bands at about 205 nm. The photosensitivities were characterized by FT-IR with different curing time. The thermal properties of samples were characterized by DSC and TGA. In addition, the solubilities and viscosity of the HBPUA-COOHs were also examined. These synthesized hyperbranched polyurethane acrylate oligomers containing carboxyl groups, which have well-defined structures with very narrow polydispersities, can be used in many fields such as coatings, adhesives and photoresists, ect.