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Several strategies are reported that allow carbon black (CB) particles to be selectively localized at the interface of polyethylene/polystyrene (PE/PS) blends used as models of twophase polyblends. A first general approach relies upon a kinetic control, i.e., the choice of such processing conditions that the CB particles are "immobilized" at the polyblend interface at least for a workable period of time. The dry premixing of the two powdery polymers and CB particles followed by compression molding is the first valuable kinetic control. A second one can be implemented during the melt blending of the immiscible polymers, which makes this strategy more attractive. Actually, CB is first dispersed in the melted polymer with which it less strongly interacts. Upon the addition and melting of the second polymer, CB particles are thermodynamically driven to this second polymer phase. The conducting particles are observed to accumulate at the polyblend interface at a rate and for a period of time that depend on the rheology of the polyblend under the processing conditions. The thermodynamically controlled localization of the CB particles at the two-phase polyblend interface is certainly the most efficient strategy, even though it is not the most general one. In this respect, CB particles have been oxidized in such a way that they cover a large range of pH. Depending on this surface property, the CB particles are spontaneously localized either in one polymer phase or at the interface. Actually, the selective localization of the CB particles changes from the PS phase to the interface and finally to the PE phase, when the pH of these particles is increased from 2.4 to 7.0.The selective localization of the CB particles at the polyblend interface is most interesting when the polymer phases are cocontinuous, since then the conducting particles can percolate at a volume fraction as small as 0.002-0.003. Furthermore, this selective modification of the polyblend interface improves the stability of the phase morphology against coalescence when the material is annealed.

The observation of aerogels submitted to a pressure of mercury indicates that this porous material is compacted and not intruded by the mercury. Consequently, the classical Washburn equation cannot be applied. A relation is established between the pressure P of compaction and the size L of the largest pores. The size of pores is estimated by using the nitrogen adsorption-desorption isotherms analysis and SEM measurements. A relation is found in which P is proportional to L−4 The new relation is applied to mercury porosimetry. Finally, a mechanical model is proposed that reproduces successfully the behavior of aerogels under high pressure of mercury.

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The local electric fields in a semicontinuous metal film are shown to exhibit giant fluctuations in the visible and infrared spectral ranges, when the dissipation in metallic grains is small. The field fluctuations result in significantly enhanced Raman scattering from semicontinuous metal films. The scaling analysis is performed to describe giant Raman scattering in the vicinity of the percolation threshold. A theory of Raman scattering from these films is developed. A numerical method based on the theory is suggested and used to calculate Raman scattering from silver semicontinuous films. Results of the simulations are compared with recent experimental observations. ͓S0163-1829͑97͒03119-6͔

Abstract. The electrical and dielectric properties of co-continuous polystyrene (PS)/poly(methylmethacrylate)(PMMA) blends loaded with carbon black (CB) of a special grade (BP 1000) have been studied. They strongly depend on the selective localization of the CB particles at the blend interface quite consistently with the double percolation concept. The interfacial localization of CB contributes to the stabilization of the phase morphology against thermal post treatment. Nevertheless, the sample annealing has a very favourable effect on the percolation threshold that decreases. The composition range in which phases are co-continuous is also increased by the addition of the filler. Dispersion of the conductance and the dielectric constant has been measured in the wide frequency range 10 −4 -10 8 Hz for blends containing 0-5 wt% CB. On the basis of these results, the mechanism of electrical transport (trapping, hopping, tunnelling, percolation) has been discussed in relation to the CB loading and the optimum loading has been identified for the electrical and dielectric properties to be stable and reproducible.

We derive a universal function for the kinetics of complex systems characterized by stretched exponential and/or power-law behaviors.This kinetic function unifies and generalizes previous theoretical attempts to describe what has been called "fractal kinetic".We discuss briefly the relation of the (n, α) kinetic formalism with the Tsallis theory of nonextensive systems.

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