Optical and thermal behavior of novel fluorinated polyimides capable of preparing colorless, transparent and flexible films

A new diamine, 1,5-bis(2-amino-4-trifluoromethylphenoxy)naphthalene (DA1524) was synthesized by the nucleophilic substitution reaction of 1,5-dihydroxynaphthalene and 4-chloro-3-nitrobenzotrifluoride in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C in ethanol. DA1524 was then utilized to prepare a novel class of CF3-containing polyimides. Intrinsic viscosities [η] of the polymer solutions at 25 °C were measured by the extrapolation of their viscosity numbers till zero concentration. M ¯ w and M ¯ n 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–vis curves were determined, and all the resulting polyimides films exhibited high optical transparency. Thermal stability of the polymers was investigated using TGA analyses. The Tg values of the polyimides obtained from their DSC plots were quantified. Solubility of the samples in a variety of organic solvents was also tested.