Polyimides reinforced with the sol‐gel derived organosilicon nanophase as low dielectric permittivity materials

Abstract

Polyimide (PI) nanocomposites prepared by the in situ generation of crosslinked organosilicon nanophase (ON) through the sol‐gel process were characterized by densities, thermally stimulated depolarization currents and dielectric relaxation spectroscopy. Both a looser molecular packing of PI chain fragments adjacent to the ON and a loose inner structure of the spatial aggregates of ON were assumed to be responsible for a non‐additive decrease of the experimental values of dielectric permittivity for the nanocomposites. The pattern of composition dependence of the apparent dielectric permittivity of the ON suggested a probability of a morphological change around the composition PAAS/MTS = 100/16 (presumably, a sort of percolation transition from small‐size, individual clusters into large‐size, infinite clusters). Thus, PI reinforced with the sol‐gel derived nanophase may have a reasonably good potential as low dielectric permittivity materials. Copyright © 2004 John Wiley & Sons, Ltd.

Preparation and properties of thermally conductive polypropylene composites

“…Dielectric relaxation spectroscopy was employed to determine the dielectric permittivity of the composites. In addition, the dielectric permittivity of the composites [52] was calculated using the models of Looyenga [40] or Lichtenecker [53], with Eqs. (8) and (9), respectively.…”

“…The deviations between calculated and measured permittivities, which increase with raising filler content, are assumed to be caused by formation of local fields. This is due to the fact that BN has a slightly higher electrical conductivity than the matrix and therefore gets polarized in the applied field [52]. The frequency dependent dielectric permittivity values for selected composites with a filler content of 30 vol.-% are presented in Figure 7.…”

Effect of clay on properties of polyimide‐clay nanocomposites

“…[10][11][12][13][14][15][16][17] The homogeneous dispersion of organically modified MMT clay in polymers would lead to enhanced thermal stability, [10][11][12][13][14][15][16] mechanical property, [10][11][12][13][16][17] corrosion resistance, 14 gas barrier, [12][13][14]17 less moisture absorption, 15,18 reduced thermal expansion coefficient, 15,[17][18] and fire-retardant in the resulting nanocomposites. Dielectric studies for PI-clay nanocomposites [18][19][20] or PI-silica nanocomposites using silica nanoparticles [21][22] and nanotubes 23 have shown low dielectric constants close to that of pristine PI. However, the application of PI-layered silicates or PI-nano silica nanocomposites as the low k materials remains hesitated because of the suspicion of wideranged dielectric permittivity of smectite clay 24 and higher intrinsic dielectric properties of bulk silica (k ¼ 3.8-4.0).…”

Physics and Chemistry of Sol-Gel Nanocomposites Formation

“…At high content of inorganic phase mechanical and thermal properties deteriorate, which is caused by aggregation of silica gel particles in the hybrid. These polyamides are promising candidates for usage in microelectronics [168], other types of sol-gel products of similar composition are promising for production of membranes with high gas transporting properties [169], ceramics [170], nonflammable nanocomposites [171], materials with low dielectric permeability [172,173] and with stable optical properties for non-linear optics, [174], etc. Also widely used are polyamide-silica gel hybrid coatings (0-20 wt% SiO 2 ), which are obtained, for example, from PI, TEOS, glycidyloxypropyl trimethoxysilane and polyamic acid (synthesized from 3, 3, 4 benzophenone tetracarboxylic dianhydride (BTDA) and 3,3 0 -Diaminodiphenyl sulfone)(DDS) [143]), combination of sol-gel technique with Scheme 4.7 Covalent binding of nanoparticles with a polymer chain by 3-glycidiloxytrimethoxy silane thermal imidization.…”