Synthesis and characterization of novel highly branched block copoly(urethane-imide)s based on pentaerythritol, different diisocyanate and aromatic dianhydride

摘要

In this work, we for the first time prepared a series of novel highly branched block copoly (urethane-imide)s (CoPUIs) successfully by the condensation polymerization of star-like prepolymers and dianhydrides, (including pyromellitic dianhydride (PMDA), 3,3',4,4'- benzophenonetetracarboxylic dianhydride, and 4,4'-oxydiphthalic anhydride) and the star-like prepolymers were synthesized from pentaerythritol (PAT) and toluene-2,4-diisocyanate (TDI) or isophorone diisocyanate. Our results revealed that it took about 40 min to complete the prepolymerization of PAT and TDI at 40°C. In addition, the imidization of the prepolymer and PMDA was successfully carried out at 120°C for 2 h. The X-ray diffractometer patterns exhibited that the resulting CoPUIs presented heterogenous structure with the d-spacing around 0.40 nm. Differential scanning calorimeter curves showed that the T_g of these CoPUIs ranged from 214 to 229°C in N_2 atmosphere. Thermogravimetric analyzer curves indicated that these synthesized CoPUIs had obviously two steps of weight loss in N_2 atmosphere due to the used monomers which decomposed at 230-235°C and 602-644°C, respectively. The solubility testing results showed that the highly branched block CoPUIs had desirable solubility in several strong polar aprotic solvents and exhibited a strong resistance to dilute acid corrosion.