Shape-controllable nanofibrous membranes with well-aligned fibers and robust mechanical properties for PM2.5 capture

In this study, design and fabrication of novel shape-controllable and aligned nanofibrous membranes with self-cleaning and robust mechanical properties is presented. Smooth and uniform nanofibers can be fabricated by blending polyamide 66 (PA66) and poly (vinyl butyral) (PVB) with a mass ratio of 6/4 during electrospinning. Subsequently, the prepared nanofibrous membranes were placed in a vacuum drying oven at a given temperature (90 °C) for heat treatment, and the morphology of the composite nanofibers was controlled by an external tensile force. It was found that the treatment temperature and external tensile force greatly affected the pore structures and orientation of the nanofiber membranes. In addition, the hydrophobicity, pore structure and mechanical properties of well-aligned nanofibrous membranes are better than those of non heat-treatment nanofibers. Moreover, the PA66/PVB nanofibrous membranes are used as air filters, and show an excellent removal efficiency of up to 99.99% for PM2.5.

SiC-fixed organophilic montmorillonite hybrids for poly(phenylene sulfide) composites with enhanced oxidation resistance

SiC-fixed organophilic montmorillonite hybrids exhibited improved dispersion and excellent antioxidant ability in a poly(phenylene sulfide) matrix.

Nonisothermal crystallization kinetics of polyphenylene sulfide composites based on organic clay modified by benzimidazolium salt

Polyphenylene sulfide (PPS)/organic clay nanocomposites were prepared by simple melt blending. A synthesized benzimidazolium salt was used to modify the sodium montmorillonite in order to improve the compatibility with the PPS. The nonisothermal crystallization kinetics of PPS/organic clay composites were investigated by differerntial scanning calorimetry(DSC). It was observed that the crystallization peak temperature of PPS/organic clay composites was higher than pure PPS at various cooling rates. Several models such as the Ozawa and Mo equation were used to characterize the nonisothermal cooling crystallization kinetics of the PPS/organic clay composites. The results indicated that the Ozawa equation was not successful, while the Mo equation was successful to describe the nanoisothermal ctystallization kinetics of PPS/organic clay nanocomposites. The results also indicated that organic clay not only served as heterogeneous nucleating agents for PPS crystallization at lower content but also restricted the mobility and diffusion of PPS chains at higher content. These results were further supported by the crystallization activation energy of the samples determined by the Kissinger method.

Kinetically trapped co-continuous polymer morphologies through intraphase gelation of nanoparticles

We describe an approach to prepare co-continuous microstructured blends of polymers and nanoparticles by formation of a percolating network of particles within one phase of a polymer mixture undergoing spinodal decomposition. Nanorods or nanospheres of CdSe were added to near-critical blends of polystyrene and poly(vinyl methyl ether) quenched to above their lower critical solution temperature. Beyond a critical loading of nanoparticles, phase separation is arrested due to the aggregation of particles into a network (or colloidal gel) within the poly(vinyl methyl ether) phase, yielding a co-continuous spinodal-like structure with a characteristic length scale of several micrometers. The critical concentration of nanorods to achieve kinetic arrest is found to be smaller than for nanospheres, which is in qualitative agreement with the expected dependence of the nanoparticle percolation threshold on aspect ratio. Compared to structural arrest by interfacial jamming, our approach avoids the necessity for neutral wetting of particles by the two phases, providing a general pathway to co-continuous micro- and nanoscopic structures.

Layering and prewetting in experimental systems: an assessment cross-referred to current theories

The first aim of this review is to assess the experimental data available about surface phase transitions at the contact between fluid bulk phases and either their vapour in the case of liquids (free interfaces) or solid substrates in general and to test their "universal" behaviour out of any consideration about critical laws, which constitute a topic by themselves. As, here, the level under consideration is only the microscopic one, wetting transitions are excluded. Our second goal is to compare these experimental data to their description by models, which are far more numerous. This imposed us to privilege, here, Cahn's and DFT theories because their way of reasoning is very close to classical thermodynamics and so, the discussion of the experimental data under examination here is facilitated with no exclusion of decisive contribution by other kinds of theories. A thorough analysis of available experiments and theoretic works makes layering appear as a general and non-wetting-dependent phenomenon exhibited by simple gases or gas mixtures on solids and also by liquid mixtures. On the other hand, though prewetting is not deeply different in essence, it is fully wetting-dependent. Both phenomena can be found in systems where interactions are very different by nature and, according to very recent models and experiments, the interplay between these interactions may lead to intertwining between both surface phenomena.