Low dielectric constant polyetherimides have been synthesized by incorporating a bisphenol A dianhydride, BPADA, and 2,7-bis(4-aminophenoxy) naphthalene (BAPN), a phenylene ether diamine. The flexible ether and larger planar naphthalene structure of BAPN led to more spacing between polymer molecules, resulting in less efficient chain packing and an increase in the free volume, thus decreasing the dielectric constant. New PEI/silica hybrid nanocomposites were prepared from this novel polyetherimide via sol-gel process. The dielectric constants were further decreased with the incorporation of silica. These synthesized PEI and nanocomposites have high thermal stability and good mechanical properties.

Rheologic behavior of the common Ryton-type poly(pheny1ene sulfide) (PPS) and Fortron PPS has been studied using a capillary rheometer. The effects of shearing rate, shearing stress, and temperature on the apparent viscosities of PPS are discussed. The non-Newtonian index and the activation energy of the viscous flow were obtained. The results show that the apparent viscosity of the Ryton PPS decreased obviously with increase of shearing rate or shearing stress, and with increase of the temperature, the apparent viscosity is not considerably decreased. On the contrary, the apparent viscosity of the Fortron PPS is more sensitive to temperature than to shearing rate and shearing stress. is a high-performance engineering thermoplastic, with good thermal stability, excellent chemical resistance, inherent flame resistance, and precision moldability. PPS resin also has excellent electrical and mechanical properties. PPS resin was produced in America by Phillips Petroleum Co. under the trade name Ryton in 1968. Ryton resin has a moderate molecular weight for injection moldings and usually should undergo a "curing" reaction upon heating in the presence of oxygen. The molecular weight of the polymer is increased by chain branching and crossing. Studies on its rheologic behavior have been reported over the last two decades.'-3 In 1985, PPS with linear and high molecular weight and toughness was commercially produced in Japan by Kureha Chemical Industry Co., which is called the second-generation PPS with the trade name F~r t r o n .~ Thermal characteristics of Fortron have been r e p~r t e d .~