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ABSTRACT:2,3,4,5,6-Pentafluorobenzonitrile (PFBN) is a valuable intermediate and it is available as a commercial product. In this paper, synthesis and characterization of novel fluorinated poly(ether nitrile)s (PEN) derived from PFBN is reported. Novel fluorinated PENs containing fluorine atoms in the main chain and pendant phenoxy group (2F-PEN) are synthesized by aromatic nucleophilic substitution reaction, of which M0 ranges from 1.77 X 10 4 to 5.16 X 104. The obtained PENs show excellent solubilities in common solvents, and 2F-PEN(6FBA) and 2F-PEN(DPE) can be cast as tough transparent films. These polymers have high thermal stabilities with the 5% weight loss temperature in the range 509-5620C and the Tg of 142-235°C, which is highly dependent on the structures.KEY WORDS Poly(ether nitrile) / Fluorine-Containing Polymer I 2,3,4,5,6-Pentafluorobenzonitrile / Nucleophilic Aromatic Substitution/ Thermal Stability/ High Tg I Solubility/ The high-performance fluorinated polymers have been receiving considerable attention as interesting advanced materials for applications as films, coatings for optical and microelectronics devices, gas separation membranes and so on. 1 -3 The incorporation of fluorine atoms into polymer chains leads to polymers with increased solubility, flame resistance, thermal stability and glass transition temperature, while also leading to decreased color, crystallinity, dielectric constant and moisture absorption. Owing these advantages, poly(aryl ether ketone)s (PEK) containing hexafluoroisopropylidene units had been prepared and studied for use in aerospace and electronic applications. 4 Recently, PEKs containing 2,3,5,6-tetrafluoro-l,4-phenylene moieties were synthesized from perfluorobenzophenone. 5 2,3,4,5,6-Pentafluorobenzoic acid (PFBA) is a valuable intermediate for pharmaceuticals, pesticides, perfumes, cosmetics and so on, and it is available as a commercial product. The authors had reported the synthesis and characterization of novel fluorinated PEKs containing 2,3,5,6-tetrafluoro-1,4-phenylene moieties derived from PFBA. 6 • 7 These fluorinated PEKs showed excellent thermal stability and solubility into common organic solvents. Moreover, the films of these PEKs possess outstanding transparency and low dielectric constants. Therefore they are expected to use a optical and electronic materials and the application study is currently underway.2,3,4,5,6-Pentafluorobenzonitrile (PFBN) is a raw material of PFBA and its commercial availability is much higher than PFBA. 2,6-Difluorobenzonitrile is commonly used as a monomer for poly(ether nitrile)s (PEN) 8 and other types of fluorinated PENs had been previously synthesized from 2,4,5,6-tetrafluoroisophthalonitrile and bisphenols by interfacial polycondensation. 9 However, polymers derived from PFBN have not be reported 290 to our knowledge. In this paper, synthesis and characterization of novel fluorinated PEN derived from PFBN is reported.

ABSTRACT:The influence of electron beam irradiation on the properties of fluorine-containing poly(aryl ether ketone)s (F-PEK), derived from 2,3,4,5,6-pentafluorobenzoic acid, was examined. Irradiation was performed with an electron beam at a dose of 3.63 ϫ 10 3 Gy s Ϫ1 for which the corresponding doses were 29.0, 51.0, and 94.5 MGy. Tensile strength at break increased up to a dose of 29.0 MGy and then decreased very slightly with irradiation. Elongation at break was more susceptible to irradiation and decreased drastically to one tenth at a dose of 29.0 MGy. Young's modulus was enhanced by the irradiation. F-PEKs were changed from elastic materials to strong and brittle materials by irradiation. Relaxation of the viscoelastic property shifted toward higher temperature by irradiation. These tensile and viscoelastic property changes were attributed to the formation of a bulkier and more rigid structure by crosslinking. The fluorine atoms attached to the 1,4-phenylene moiety in F-PEKs were surprisingly susceptible to the irradiation and were completely lost at a dose of 29.0 MGy. The -electron conjugated aromatic structure was concurrently developed during irradiation. Further, polar functional groups such as carboxyl group and ester group were generated by chain scission and rearrangement. The F-PEKs retained their good transparency and the thermal stability was significantly improved after irradiation.

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