Dielectric polystyrene films

Fig. 7 Dielectric loss vs. temperature at different frequencies, as indicated, for a thin polystyrene film of 89 nm, before and after 24 hours of annealing at 180 °C in a pure nitrogen atmosphere...

Even if some polymers might be hydrophobic in the bulk, concerns about possible water adsorption effects in thin films are justified, because of the preponderant role of the interface in confinement. For example, negligible water adsorption is reported in the handbook of polymers for polystyrene in the bulk 0.05% at 23 °C and 50% relative humidity. In spite of this, strong water adsorption-desorption effects were observed in thin polystyrene films the dielectric loss decreased with more than one decade when a thin film was measured in a dry nitrogen atmosphere and after 2 horns of annealing at 135 °C (Fig. 9, example for a film thickness of 223 nm). A pronounced decrease of s ( 20% at 1 Hz) was detected as well. 

For thin polystyrene films annealed for 12 hours at 150 °C in high vacuum (10-6 mbar) and measured in a pure nitrogen atmosphere the dynamic glass transition was characterized using two experimental techniques capacitive scanning dilatometry and Broadband Dielectric Spectroscopy. Data from the first method are presented in Fig. 15a, showing the real part of the complex capacity at 1 MHz as a function of temperature for a thin PS film of 33 nm. 

In terms of their dielectric response, thin polymer films turn out to be thermally stable if kept in an inert atmosphere (i.e., flow of pure nitrogen), even for long times at temperatures well above the glass transition. An example is given in Fig. 3 for a thin polystyrene film of 89 nm After 24 hours at 180°C in a pure nitrogen atmosphere, the sample was measured again and no changes in the dielectric response were detected. 

Our experimental results suggest that the switching mechanism is not due to the formation of conductive filaments between the two metal electrodes, which was observed in a polymer film by others [31,32]. It is unlikely that filament formation is the reason for the electronic transitions in our device, since the electrical behavior of our device is strongly dependent on the structure and concentration of the gold nanoparticles. In addition, ac impedance studies, from 20 to 10 Hz (Figure 8.8), indicate that the electronic transitions in our device are different from the dielectric breakdown found in polymer films. We observed dielectric breakdown in a device with a polystyrene film sandwiched between two A1... 

One Step Polymerization of Sulfonated Polystyrene Films in a Dielectric Barrier Discharge. Plasma Process. PolyrtL, Vol. 7, pp. 836-845 Michel, M. Bour, J. Petersen, J. Amoult, C. Ettingshausen, F. Roth, C Ruch, D. (2010). 

Film structures with domains that form elements with complementary functions of (a) solar cells, obtained using electron-donating polyfluorene copolymer APFO-3 and electron-accepting fullerene derivative PCBM and (b) of electronic circuitries using conjugated poly(3-alkylthiophene) P3AT and dielectric polystyrene PS. 

Essentially polymer-film capacitors comprise dielectric films (polymer or paper or both together) interleaved with aluminium electrodes, either as aluminium foil or, more commonly, in the form of a layer evaporated directly on the dielectric, and rolled together. They are sealed in an aluminium can or in epoxy resin. Because the dielectric films and evaporated electrodes have thicknesses of only a few microns and about 0.025 /mi respectively, volumetric efficiencies can be high. The dielectric films are polystyrene, polypropylene, polyester, polycarbonate or paper paper dielectrics are always impregnated with an insulating liquid. 

Conversely, on a time scale of minutes, both the real part of the complex sample capacity (and correspondingly s ) and the dielectric loss increased when a polystyrene thin film (20 nm) was replaced from a dry nitrogen atmosphere and exposed to ambient water vapor at room temperature (Fig. 10). 

Bai [3] surface modified polymeric low dielectric constant gate insulator films consisting of polystyrene/polyacrylate block copolymers, (II), having an e 4.6. Perfluoroether acyl oligothiophenes, (III), prepared by Gerlach [4] were also effective as low dielectric constant gate insulators. 

Common polymers such as polystyrene (PS) and polymethylmethacrylate (PMMA) have been used as gate dielectric materials [7,20,46]. Their ready availability made them some of the early polymers investigated by researchers in the field [11,39,47]. However, the low capacitances of these films made them less attractive than other polymers. Poly(4-methylstyrene) has been explored as a possible polarizable gate insulator [48]. 

Figure 3.2.6). Narrowly dispersed polystyrene (synthesized by atom transfer radical polymerization [polydispersity < 1.1]) was end fnnctionized with a phosphonate moiety that binds strongly to titanium oxide. The combination of narrowly dispersed titanium oxide and narrowly dispersed phosponate-terminated polystyrene generates a narrowly dispersed core-shell architecture as measured by dynamic light scattering, which can be spun into dielectric films. The covalent coating of polystyrene around titanium oxide is helpful at preventing aggregation of the nanoparticles in organic dispersion and in thin films.

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