Preparation and characterization of fluorine‐containing aromatic condensation polymers, 4. Preparation and characterization of fluorine‐containing aromatic polyazomethines and copolyazomethines from perfluoroisopropylidene group‐containing aromatic diamines and/or isopropylidene group‐containing aromatic diamines and phthaladehydes

Abstract

AbstractA series of novel fluorine‐containing aromatic homopolyazomethines and copolyazomethines were synthesized by solution polycondensation of perfluoroisopropylidene (perfluoropropane‐2,2‐diyl) group‐containing aromatic diamines, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]‐1,1,1,3,3,3‐hexafluoropropane (4,4′‐[1,1,1,3,3,3‐hexafluoropropane‐2,2‐diylbis(1,4‐phenyleneoxy)]dianiline (1a)) and 2,2‐bis(4‐aminophenyl)‐1,1,1,3,3,3‐hexafluoropropane (4,4′‐(1,1,1,3,3,3‐hexafluoropropane‐2,2‐diyl)dianiline (1b)), and/or the corresponding analogous isopropylidene group‐containing aromatic diamines, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane (4,4′‐[isopropylidenebis(1,4‐phenyleneoxy)]dianiline (1c)) and 2,2‐bis(4‐aminophenyl)propane (4,4′‐isopropylidenedianiline (1d)), with terephthalaldehyde (2a) and isophthaladehyde (2b). The effect of fluorine substitution on the synthesis and properties of these polymers was investigated by comparison with those of the corresponding homopolyazomethines but without fluorine. Film‐forming fluorine‐containing polyazomethines with reduced viscosities up to ηred = 0,44 dL · g−1 were obtained in high yields by using m‐cresol as reaction medium. Incorporation of perfluoroisopropylidene groups in the polyazomethine backbone greatly enhanced the solubility of the polymers in various organic solvents including chloroform and tetrahydrofuran. Their thermal stability was also successfully improved by the introduction of fluorine, and both the temperatures of 5% and 10% weight loss in air increased monotonically with the increase of the fluorine content. The surface properties of the films or the contact angles formed by water and diiodomethane were, however, scarcely affected by fluorine substitution. The mechanical properties of the films, such as tensile strength and initial modulus, fairly decreased by the modification.