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The ac electrical properties of acetylene black composites mixed into ethylene butylacrylate copolymer (EBA) and into poly (methyl methacrylate) (PMMA) have been measured in thermal cycling and isothermal annealing experiments. The results show that changes in electrical properties are due to rearrangement of gaps between the carbon black aggregates. This has been concluded using an exponent z that relates the critical frequency ωc denoting the crossover of the conductivity from the dc-plateau to its frequency-dependent part to the dc conductivity, σdc, according to ωc ∝σdcz. Below the melting range of EBA and the glass transition of PMMA z is about one corresponding to strong variation of the conductivity and weak dependence of the permittivity on the gaps. Above the melting range of EBA z is about 1.5, indicating strong dependence of both the conductivity and the permittivity on the gaps, as predicted by percolation theory. This was not found in the PMMA composites above the glass transition. We conclude that the polymer matrix affects the nature of the gaps between carbon black aggregates, either allowing their size to vary continuously (z about 1) or letting them open and close (z about 1.5).

The dielectric behaviour of various carbon black polymer composites has been characterized by the critical frequency ωc denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour. The critical frequency can be related to the dc conductivity using a power law, ωc∝σdcz, with the exponent z. Presently accepted models predict z to be greater than one when varying the filler content. However, in accordance with published experimental results this work shows that z is rather close to one indicating a nearly constant static permittivity. Furthermore, the above power law makes it possible to describe all investigated compounds using a single master curve ranging over ten decades of dc conductivity. These findings are explained by a qualitative percolation model based on electron tunnelling. Increasing the dc conductivity along the percolation curve does not require the establishment of more physical links between carbon black aggregates. Rather, new conduction paths of nearly the same lengths but with higher tunnelling probability due to smaller gaps satisfy the percolation theory. This scenario allows the number of capacitive gaps to be nearly constant making z near one.

Current noise and conductivity in composites of conductive spherical polyaniline particles covered with non-conductive poly(vinyl alcohol) layers dispersed in the same polymer medium were investigated. As the polyaniline particles are fully separated by insulating material, conductive percolation is not possible and electrical conductivity occurs only by thermally assisted charge hopping or possibly tunnelling. An interpretation in terms of quiet conductive paths through the polyaniline particles and noisy conductance through the poly(vinyl alcohol) matrix is given.

Inelastic light scattering from the free surface of the liquid crystal ethyl p-[(p-methoxybenzylidene)amino] cinnamate (EAC) has been used to determine its surface tension and viscosities in both the nematic and smectic-A mesophases. In the nematic mesophase (117-138 ?C) the molecules are parallel to the surface and are aligned by the 2 kG magnetic field. At 133 ?C the surface tension (dyn cm?1) and viscosities (P) (?; ?1, ?2, ?3) are (47?5?2?5; 0?09?0?02, 0?14?0?02, 0?30?0?10), and at 120 ?C they are (50?0?2?5; 0?17?0?04, 0?18?0?02, 0?30?0?15). For the smectic-A mesophase (107-117 ?C) the molecules are perpendicular to the free surface and to the smectic-A layers. The scattering spectrum is independent of ?2 in this case. Thus at 109 ?C the three parameters (?; ?1, ?3) were obtained: (52?5?2?5; 0?19?0?04, 0?70?0?30).

The DC electrical resistances of certain chloroprene rubbers with carbon black filling exhibit positive temperature coefficients (PTC effect) for certain concentrations of the conductive filler. The electrical noise exhibited by these rubbers has been studied. The thermal noise is shown to obey Nyquist's theorem to a good approximation. The current noise shows a 1/f frequency dependence, and the noise power is proportional to the square of the applied bias voltage. This applies to samples exhibiting a wide range of resistivities, from over 107 Omega cm (20% carbon black) to under 100 Omega cm (35% carbon black by weight).

Laser light scattering and optical mixing spectroscopic techniques have been used to study the dispersion relation of kHz frequency thermally excited capillary waves on the free surfaces of p-azoxyanisole and p-azoxyphenetole. The experimentally determined dispersion relation agrees well with the predictions of hydrodynamic theory, both with respect to the frequency and to the damping of the waves.

The spectrum of light scattered inelastically from the nematic liquid crystal p-azoxyphenetole has been studied by optical-mixing spectroscopy. The experimental results support recent hydrodynamic theories of fluctuations in nematic liquid crystals. The unknown Frank elastic constants K2 and K3 (in CGS units) have been determined to be 6?1 ? 10?7 ?15% and 17?2 ? 10?7 ?25%, respectively.

Studies of the crystallization of the free surface of p-azoxyphenetole (PAP) show that for a surface supercooling greater than about 3-6°C anomalously fast crystallization takes place. Typical propagation speeds are 10-15 cm s−1, compared with only a few mm s−1 for less supercooling. p-azoxyanisole (PAA) does not appear to show the fast crystallization even when supercooled as much as 12°C.

Possible spatial effects in an extended world dynamics model including diffusion are discussed. The rate equations are similar to those describing autocatalytic chemical reactions, which exhibit spatial inhomogeneities under certain conditions. The extended world dynamics model should exhibit similar spatial structure due to strong positive feedback loops (autocatalytic steps).