Flexible, low-colored and transparent thin films prepared from new thermo-stable and organo-soluble poly(amide-imide)s

An imide ring-containing diacid, 2,2′-diphenyl-4,4′-bis(N-trimellitoyl)diphenyl ether (PTPE) was synthesized through a three-step pathway starting from 2,2′-diiodo-4,4′-dinitrodiphenyl ether. A series of novel aromatic poly(amide-imide)s having bulky phenyl pendant groups at 2,2′-disubstituted positions were then prepared via a direct phosphorylation polycondensation between PTPE and various aromatic diamines. Chemical structure of the new monomer as well as the resulted polymers was thoroughly confirmed by IR and NMR spectroscopic methods. Intrinsic viscosities [η] of the polymer solutions at 25 °C were measured by the extrapolation of their viscosity numbers till zero concentration. Mw¯ and Mn¯ values of the resulting polymers were determined using gel-permeation chromatography (GPC). The polymers showed a good film-forming ability, and some characteristics of their thin films including color and flexibility were investigated qualitatively. In addition, the absorption edge values (λ0) obtained from their UV curves were determined, and all the resulting poly(amide-imide)s films exhibited high optical transparency. Thermal stability of the polymers using their TGA thermograms was investigated. The Tg values of the poly(amide-imide)s obtained from their DSC plots were also quantified. Crystallinity amount of the prepared macromolecules was evaluated using wide-angle X-ray diffraction (XRD). Furthermore, solubility of the samples in a variety of organic solvents including dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), pyridine, tetrahydrofuran (THF), and toluene was tested.