The effect of selective localization of silicon carbide (SiC) and polystyrene (PS)-coated SiC (p-SiC) nanoparticles on the thermal conductivity and flame retardancy of immiscible PS/poly(vinylidene fluoride) (PVDF) blends has been systematically studied. The scanning electron microscopy (SEM) images reveal that SiC and p-SiC nanoparticles have different selective localizations in the PS/PVDF blends. The melting and crystallization behaviors of the PVDF component investigated by using differential scanning calorimetry are consistent with the SEM results. To reduce the volume fraction of fillers in the composites, a cocontinuous structure of PS/PVDF has also been built up. The cocontinuity window for PS/PVDF blends is ∼30-70 vol % according to the selective solvent dissolution technique. The selective localization of SiC in the PVDF phase of the PS/PVDF 70/30 blends produces a slightly higher thermal conductivity than that of p-SiC in the PS phase of the PS/PVDF 30/70 blends. However, the composites with selective localization of p-SiC exhibit the best combined properties of thermal conductivity and flame retardancy.

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In this work, the dielectric properties of immiscible polystyrene (PS)/poly(vinylidene fluoride) (PVDF) blends are tuned by selectively localizing carbon black (CB) nanoparticles in different phases. The PS/PVDF blends have a wide window of cocontinuity (ca. 30-80 vol % in terms of the volume fraction of PS component (v(PS))). The selective localization of CB nanoparticles is achieved by using the masterbatch process during melt mixing. For the volume ratio PS/PVDF 1/1 and the volume fraction of CB nanoparticles (v(CB)) below but close to the percolation threshold (v(c)(CB)), the selective localization of CB nanoparticles in PVDF phase produces higher dielectric constant (ε) than that in PS phase, whereas the ε of the ternary mixtures without selective localization of fillers is in the middle. For the volume ratios PS/PVDF 1/2 and 2/1, the selective location of CB nanoparticles in different phases can be used to easily tune the system from conductive to insulating or inverse, which might have potential applications in industry. The fillers are found to be "fixed" in the masterbatch of PS or PVDF component and there is no migration of the fillers to another phase occurring during the further mixing process for the mixing time up to 30 min. Furthermore, the addition of CB nanoparticles to the polymer matrix is found to induce the brittle-ductile transition in the system and increase the compatibility between the immiscible PS and PVDF components, which should benefit the mechanical properties.

A nanocomposite with ultra-low percolation threshold and high dielectric performance is prepared by controlling the localization of multiwalled carbon nanotubes (MWNTs) in one phase of a ternary continuous polymer blend system through melt processing. Polystyrene (PS), poly(vinylidene fluoride) (PVDF), and poly(methyl methacrylate) (PMMA) can form a ternary continuous structure when the volume fractions of PS, PVDF and PMMA are 70 vol%, 20 vol%, and 10 vol%, respectively. The PS is a continuous matrix (sea-phase) whereas the other two phases are interconnected threads (the PVDF is situated as the core while the PMMA is the shell, and the thickness of the PMMA shell is about 1 mm). Adding PMMA could improve the compatibility between the PS and PVDF components. Selective distribution of MWNTs in the PMMA shell is achieved through a combination of PMMA modified MWNTs and appropriate processing procedures. The composite shows an ultra-low percolation threshold of ca.0.3 wt%. When the weight fraction of PMMA modified MWNTs is 0.4 wt%, the dielectric constant of the composite is as high as 182 (at 100 Hz), which is about 60 times higher than that of a pure PS matrix.The composite's dielectric properties have excellent temperature stability. This approach can provide a new and low-cost route to design high-performance dielectric materials with ultra-low percolation thresholds.