Light-Color Soluble Polyimides Based on α,α'-Bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]-1,3-diisopropylbenzene and Aromatic Dianhydrides

A fluorine-containing crystalline diamine, � ,� 0 -bis(4-(4-amino-2-trifluoromethylphenoxy)phenyl)- 1,3-diisopropylbenzene (II), was prepared through nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride and � ,� 0 -bis(4-hydroxyphenyl)-1,3-diisopropyl in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. A series of polyimides (PIs) Va{f were then synthesized from this diamine (II) by polymer- izing with various commercially available aromatic dianhydrides (pyromellitic dianhydride (PMDA, IIIa), 3,3 0 ,4,4 0 - benzopheno tetracarboxylic dianhydride (BTDA, IIIb), 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride (BPDA, IIIc), di- phenylsulfone-3,3 0 ,4,4 0 -tetracarboxylic dianhydride (DSDA, IIId), 4,4 0 -oxydiphthalic anhydride (ODPA, IIIe) and 4,4 0 - hexafluoro isopropylidenediphthalic anhydride (6FDA, IIIf)) via thermal (H) or chemical (C) imidization methods. The polyimides had inherent viscosities ranging from 0.60 to 0.95 dL/g. Except for the thermal imidization of Vb(H), the V- series polyimides were readily soluble in amide-type solvents, such as N-Methyl-2-pyrrolidone (NMP), N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO), and also soluble even in less polar solvents such as m-cresol or pyridine. Most polyimides (film samples) had good tensile strengths of 70 to 110 MPa, elongations at break of 8 to 13% (except for Vc, 37%), and initial moduli of 1.7 to 2.0 GPa. The glass-tran- sition temperatures of V-series polyimides were in 182-202 � C, and had good thermal stability of 10% weight loss tem- peratures (491-541 � C in nitrogen or 495-537 � C in air), and char yields at 800 � C in nitrogen ranging 46-61 wt %. Ex- cept for Va,b series, the V(H) series had cutoff wavelengths between 364.5 to 399.5 nm and the b � (yellowness index) values ranging from 12.7 to 39.5. The polyimides were found to possess low moisture absorption in the range of 0.19- 0.91 wt %. (doi:10.1295/polymj.38.457)