Synthesis and Characterization of Highly Branched Poly(urethane-imide)s

A series of novel highly branched poly(urethane-imide)s (Pins) were first successfully prepared by a two-step method with toluene-2,4-diisocyanate (TDI), pentaerythritol (PAT) and dianhydrides, including pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic anhydride (ODPA). It was found that the prepolymerization of PAT and TDI at 40 degrees C was ascertained to be 40 minutes. And the imidization of the prepolymer and PMDA was successfuly carried out after 120 degrees C for 2 hours. The XRD demonstrated that the obtained highly branched PUIs pre- sented semicrystalline aggregation structure which had clear crystal phase with the d-spacing around 0.39 nm. TGA curves exhibited that these highly branched PUIs had obviously two steps of weight loss attributed to the urethane chain segment and imide chain segment, respectively. The solubility testing indicated that the highly branched PUIs exhibited desirable solubility in various polar aprotic solvents, and were also resistant to dilute acid corrosion.