Journal of Polymer Science Part A: Polymer Chemistry, Vol.38, No.4, 715-723, 2000
Preparation and properties of imide-containing elastic polymers from elastic polyureas and pyromellitic dianhydride
A new approach to obtain imide-containing elastic polymers (IEPs) via elastic and high-molecular-weight polyureas, which were prepared from alpha-(4-aminobenzoyl)-omega-[(4-aminobenzoyl)oxy] -poly(oxytetramethylene) and the conventional diisocyanates such as tolylene-2,4-diisocyanate(2,4-TDI), tolylene-2,6-diisocyanate(2,6-TDI), and 4,4'-diphenylmethanediisocyanate (MDI), was investigated. IEP solutions were prepared in high yield by the reaction of the polyureas with pyromellitic dianhydride in N-methyl-2-pyrrolidone (NMP) at 165 degrees C for 3.7-5.2 h. IEPs were obtained by the thermal treatment at 200 degrees C for 4 h in vacuo after NMP was evaporated from the resulting IEP solutions. We assumed a mechanism of the reaction via N-acylurea from the identification of imide linkage and amid acid group in IEP solutions. NMR and FTIR analyses confirmed that IEPs were segmented polymers composed of imide hard segment and poly(tetramethylene oxide) (PTMO) soft segment. The dynamic mechanical and thermal analyses indicated that the IEPs prepared from 2,6-TDI and MDI showed a glass-transition temperature (T-g) at about -60 degrees C, corresponding to T-g of PTMO segment, and suggested that microphase-separation between the imide segment and the PTMO segment occured in them. TGA studies indicated the 10% weight-loss temperatures (T-10) under air for IEPs were in the temperature range of 343-374 degrees C. IEPs prepared from 2,6-TDI and MDI showed excellent tensile properties and good solvent resistance.
Keywords:imide-containing elastic polymer;polyureas;diisocyanate;dianhydride;N-acylurea;microphase-separation;glass-transition temperature;tensile properties;solvent resistance