Polyethers dielectric properties

Dielectric Properties and Electret Behavior of Complexed Polyethers... 

It is interesting to mention that the first truly synthetic (not based on natural products) polymer material was bakelite obtained in 1907 via polycondensation of phenol and formaldehyde. This material had good dielectric properties and was used mainly as an electrical insulator. The most famous polycondensation polymer is probably nylon belonging to the class of polyamides. Other common classes of polycondensation polymers are polyesters (like polyethylene terephthalate), polysiloxanes, polycarbonates, polysulfides, polyethers and polyimides. 

The polyether sulfones are amorphous and have high glass transition temperatures of between 190 and 290° C. They have good creep behavior, dielectric properties, and thermal and hydrolytic resistance. They are suitable for use in engineering parts, electrical components, as pan and saucepan coatings, and also for the removal of salt from seawater when used in membrane form as sulfonated products. 

Wintersgill, M. C. and Fontanella, J. J. Low-frequency dielectric properties of polyether electrolytes. In Polymer electrolyte reviews II, J. R.MacCallum and C. A.Vincent (Eds.), Elservier Applied Science London, pp. 43-60 (1987). 

Faruque H S and Lacabanne C (1987) Anelastic and dielectric properties of polyether-... 

Recently the synthesis and characterization of novel fluorinated poly(aryl ether)s containing perfluorophenylene moieties " " was also reported. These fluorinated polyethers were prepared by reaction of decafluorobiphenyl with bisphenols. These polymers exhibit low dielectric constants, low moisture absorption, and excellent thermal and mechanical properties. Tough, transparent films of the polymers were prepared by solution-casting or compression-molding. The fluorinated poly(aryl ether)s containing perfluorophenylene moieties are good candidates for use as coatings in microelectronics applications. 

The discriminative uptake of alkali metal cations by biological systems, through their membranes, has been an area of much interest. In the membrane, the cations must pass through a lipid bilayer of low dielectric constant and this has led to the proposition that the cation could be selectively transferred via a carrier molecule, or through a suitably donor-lined pore.7-9 As a consequence of their selective properties, the polyethers and cryptands have been investigated as speculative models for the above process and selectivity sequences have been established. 

Much attention has been paid to the synthesis of fluorine-containing condensation polymers because of their unique properties (43) and different classes of polymers including polyethers, polyesters, polycarbonates, polyamides, polyurethanes, polyimides, polybenzimidazoles, and epoxy prepolymers containing pendent or backbone-incorporated bis-trifluoromethyl groups have been developed. These polymers exhibit promise as film formers, gas separation membranes, seals, soluble polymers, coatings, adhesives, and in other high temperature applications (103,104). Such polymers show increased solubility, glass-transition temperature, flame resistance, thermal stability, oxidation and environmental stability, decreased color, crystallinity, dielectric constant, and water absorption. 

J. Borah, S. S. Mahapatra, D. Saikia and N. Karak, Physical, thermal, dielectric and chemical properties of a hyperbranched polyether and its linear analog , Polym Degrad Stabil, 2006,91,2911-16. 

Special technical properties of conventional urethanes are superior electrical resistance with a dielectric constant normally of 3 or less, only marginally dependent upon temperature. Dielectric strength is 20-32 kV mm" A typical set of electrical properties is given in Table 12.1 which demonstrates their relative water insensitivity and also the ability to blend them with standard polyesters and polyethers. 

Considerable attention has been devoted to the preparation of fluorine-containing polymers because of their unique properties and high temperature performance (I). Recently we reported the preparation and characterization of novel fluorine-containing polyimides and polyethers which exhibit low moisture absorption and low dielectric constants (2, 3). Fluorinated polyimides absorb 1 wt% water and have dielectric constants of about 2.8 (all dielectric constants reported in this paper were measured at 10 kHz) vtdiereas their non-fluorinated analogs absorb as much as 3 wt% water and have dielectric constants of about 3.2. Fluorinated polyarylethers, which are free of polar groups such as ketones, imides and sulfones, absorb as little as 0.1 wt% water and have dielectric constants less than 2.8. 

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