Dielectric Properties of Bisphenol A Polycarbonate and Its Tethered Nitrile Analogue

Abstract

The relative permittivity and dielectric strength have been determined for a bisphenol A polycarbonate (BPA-PC), in which a cyanoethyl group has been substituted for one of the geminal dimethyl groups. The new material (CN-PC) has a glass transition temperature that is 19 K higher than that for BPA-PC. In addition, the dielectric strength of CN-PC, 405 V/μm, is somewhat smaller than that for BPA-PC, 620 V/μm. The relative permittivity was determined from 10 to 10 5 Hz over a wide temperature range and at pressures up to 0.25 GPa. While the real part of the relative permittivity at 10 3 Hz and room temperature for BPA-PC is about 3, that for CN-PC is found to be greater than 4. Correspondingly, the γ relaxation region in CN-PC is very strong. For the γ relaxation, a strong increase in peak height as temperature increases and a strong decrease in peak height as pressure increases are observed. A relaxation is found at temperatures higher than the γ relaxation. This process is labeled as the β relaxation because it appears to be related to the β relaxation in BPA-PC in that the strength and position depend on the history of the material. The effects of pressure on the γ relaxation for both CN-PC and BPA-PC are quite large and similar to those previously seen for the γ relaxation in a fluorinated tetraaryl bisphenol A polycarbonate (DiF p-TABPA-PC). In fact, the activation volume is found to be approximately the same for all three BPA-PC-based materials despite wide variations in both peak position and peak height. Finally, computer studies of the model compounds, 4,4′-diphenylpentanenitrile and diphenyl carbonate, were carried out. Both provide insight into the nature of the γ relaxation with the latter yielding an activation volume in approximate agreement with the experimental values.

Enhancing electrical energy storage using polar polyimides with nitrile groups directly attached to the main chain

“…22,23 The idea is to utilize the free volume in high T g polymers to allow relatively free rotation of individual dipoles (i.e., sub-T g transitions 24 ) in order to enhance the dielectric constant while keeping dielectric loss low. 28 Stimulated by the above promising work, we here focus on high performance polyimides (PIs), which are attractive materials for use in highly aggressive environments because of their high T g , mechanical toughness, and resistance to solvents, radiation, heat and oxidation. 25,26 For example, poly(4-vinylbenzylcyanide) was reported to exhibit a dielectric constant as high as 7.0 at 100 kHz.…”

“…This can be explained by the rigid structure of the PIs, which does not allow dipoles to turn. Bendler et al 28 reported a study attaching cyanomethylene groups to bisphenol A polycarbonate (PC), having a CH 2 group between the main chain and the nitrile group so that the dipole could rotate more freely in the side group. Also, from Fig.…”

High‐Temperature and High‐Energy‐Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6‐dimethyl‐1,4‐phenylene oxide)

“…Meanwhile,t he relatively low melting temperature (T m )o fa round 125 8 8Cp revents high-temperature operation. Thesecond example is adipolar glass polymer (note that the magnetic counterpart is as pin glass [11] ), where isolated molecular dipoles exhibit weak dipole-dipole interactions owing to the limited amount of free volume in glassy polymers.M ost dipolar glass polymers utilize highly polar groups such as nitrile [12] (dipole moment of 3.9 D) and sulfone [13] (4.5 D) groups.Relatively high dielectric constants in the range of 4-15 have been demonstrated for these dipolar glasses. [12][13] However, their glass transition temperatures (T g ) are relatively low and cannot meet the requirement of 150 8 8C ambient temperature for operation.…”

Mono‐ and bifunctional six‐membered cyclic carbonates synthesized by diphenyl carbonate toward networked polycarbonate films

“…Aromatic polycarbonates, as exemplified by bisphenol A‐based polycarbonates, are one of widely‐used polymers in various industrial applications because of their well transparency, high thermal stability, and mechanical properties . While, aliphatic polycarbonates feature biocompatibility and degradability, which inspires many scientists to explore the application to carriers of drugs and genes .…”