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ABSTRACT:A novel fluorinated diamine monomer, 3,3-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]phthalide (II), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride with phenolphthalein in the presence of potassium carbonate to yield the intermediate dinitro compound I, followed by catalytic reduction with hydrazine and Pd/C. Polyimides V were synthesized from diamine II and various aromatic dianhydrides III a{f via thermal or chemical imidization of poly(amic acid)s. These polymers had inherent viscosities ranging from 0.63 to 0.95 dL/g and were soluble in a variety of organic solvents. V a{f films had tensile strengths of 105-125 MPa, elongations to break of 9-12%, and initial modulus of 2.35-2.65 GPa. The glass transition temperatures of these polymers were recorded 259-320 C, and no significant weight loss was observed below a temperature of 500 C in nitrogen or in air. Compared with nonfluorinated homologues VI, V showed better solubility and lower color intensity, dielectric constant (2.70-3.11 at 1 MHz), and moisture absorption (0.12-0.27 wt %). In particular, V c{f afforded lightly colored films, which had cutoff wavelengths lower than 380 nm and yellowness index ( Aromatic polyimides are well known as polymer materials of high performance for their excellent thermal stabilities and balanced mechanical and electric properties.1-6 They are mainly used in the aerospace and electronics industries in the form of films and moldings. Moreover, optical transparency of polyimide films is of special importance in some applications such as flexible solar radiation protectors, 7 orientation films in liquid crystal display devices, 8 optical waveguides for communication interconnects, 9 and optical half-waveplates for planar lightwave circuits. 10 However, the wholly aromatic polyimides strongly absorb in the visible region of their UV-vis spectra and are pale yellow or deep reddish yellow because of their highly conjugated aromatic structures and/or the intermolecular charge-transfer complex (CTC) formation; besides, they are difficult to process because of high softening temperatures and limited solubility in commercially available solvents.A low dielectric constant is one of the most attractive properties of polyimide materials for electronic applications.11 One of the most effective methods to decrease the dielectric constant is to introduce fluorine atoms into polyimide materials. 12 As is well-known, the fluorine atom has unique characteristics, such as high electronegativity and low electric polarity. These properties give fluorinated polymers attractive features such as water and oil repellence, low permittivity, low refractive indices, resistance to wear and abrasion, and thermal and chemical stability. Fluorination is also known to enhance the solubility and optical transparency and to lower moisture absorption of polyimides. [13][14][15] In our previous papers, 16,17 we have successfully used the alylene ether-containing cardo diamines of 3,3-bis[4-(4-aminopheno...

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KEY WORDSFluorine-Containing Polyimides / Organosoluble / Color Intensity / Dielectric Property / 1,2-Bis(4-amino-2-trifluoromethylphenoxy)benzene / Aromatic polyimides are well known as polymer materials of high performance for their excellent thermal stabilities and balanced mechanical and electric properties. [1][2][3][4][5][6][7] Polyimides are mainly used in the aerospace and electronics industries in the form of films and moldings. Optical transparency of polyimide films is special importance in some applications such as flexible solar radiation protectors, 8 orientation films in liquid crystal display devices, 9 optical waveguides for communication interconnects, 10 and optical half-waveplates for planar lightwave circuits. 11 However, the wholly aromatic polyimides strongly absorb in the visible region of their UV-Vis spectra and are pale yellow or deep reddish yellow because of their highly conjugated aromatic structures and/or the intermolecular chargetransfer complex (CTC) formation; besides, they are difficult to process because of high softening temperatures and limited solubility in commercially available solvents.Aromatic polyimides possess many useful properties and are increasingly being required by the electronic circuit industry. 5, 12 A low dielectric constant is one of the most attractive properties of polyimide materials for electronic applications. One of the most effective methods to decrease the dielectric constant is to introduce fluorine atoms into polyimide materials. 12 Fluorination is also known to enhance the solubility and optical transparency of polyimides. [13][14][15] Therefore, it is expected that fluorinated polyimides will be widely applied in electro-optical and semiconductor industries.Recent studies demonstrated that polyimides derived from ether-bridged aromatic diamines with trifluoromethyl (3F) groups, such as 1,3-or 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, are soluble and high temperature polymer materials with low dielectric constant, high optical transparency, † To whom correspondence should be addressed. and low birefringence. 16,17 In this study, a highpurity CF 3 -containing diamine, 1,2-bis(4-amino-2-trifluoromethylphenoxy)benzene II, was synthesized by modificatory method and subsequently polycondensed with various commercially available aromatic dianhydrides to produce a series of fluorinated polyimides V a-f . These polymers were subjected to solubility, thermal, optical, dielectric property measurements and compared to analogous polyimides VI a-f 18 prepared from a nonfluorinated diamine monomer, 1,2-bis(4-aminophenoxy)benzene. EXPERIMENTAL MaterialsCatechol (Acros) and 2-chloro-5-nitrobenzotrifluoride (Acros) were used as received. Pyromellitic dianhydride (PMDA or III a ; Lancaster), 3,3 ,4,4 -benzophenonetetracarboxylic dianhydride (BTDA or III b ; Acros), diphenylsulfone-3,3 ,4,4 -tetracarboxylic dianhydride (DSDA or III d ; New Japan Chemical Co.) and 4,4 -oxydiphthalic dianhydride (ODPA or III e ; Chriskev) were recrystallized from acetic anhy...

Three diimide-diacids, 2,2-bis[4-(4-trimellitimidophenoxy)phenyl]hexafluoropropane (I-A), 2,2-bis[4-(4-trimellitimidophenoxy)phenyl]propane (I-B), and 5,5Ј-bis[4-(4-trimellitimidophenoxy)phenyl]hexahydro-4,7-methanoindan (I-C), were prepared by the azeotropic condensation of trimellitic anhydride with three analogous diamines. Three series of alternating aromatic poly(arylate-imide)s, having inherent viscosities of 0.41-0.82 dL/g, were synthesized from these diimide-diacids (I-A, I-B, and I-C) with various bisphenols by direct polycondensation using diphenyl chlorophosphate and pyridine as condensing agents. All of the polymers were readily soluble in a variety of organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and even in the less polar tetrahydrofuran. These polymers could be cast into transparent and tough films, which had strength at break values ranging from 73 to 98 MPa, elongation at break from 6 to 11%, and initial modulus from 1.6 to 2.2 GPa. The softening temperatures of the polymers were recorded at 145-248°C. They had 10% weight loss at a temperature above 450°C and left 35-51% residue even at 800°C in nitrogen.