[Show abstract][Hide abstract] ABSTRACT: Two poly(vinylidene fluoride)(PVDF)/carbon nanotube (CNT) composites are prepared by solution sonication and mechanical mixture approaches. It is found that α-phase coexists with β-phase in the composite prepared by sonicating the PVDF/CNT mixture solution, while no β-phase can be observed in the composite prepared from the mechanical mixture route. With the help of the density functional theory calculations, it is explained that a large amount of energy is required for transforming trans−gauche−trans−gauche′ (TGTG′) into trans−trans (TT) conformations and the TT molecular chain can be bound on the CNT surface tightly. The emergence of β-phases is independent of zigzag carbon atoms on the CNT surface. The formation mechanism of β-phase is proposed based on the theoretical calculations and experimental results.
[Show abstract][Hide abstract] ABSTRACT: In this study, the reinforcing effects of carbon black (CB) and carbon nanotube (CNT) complex fillers on the properties of isotactic polypropylene (iPP) nanocomposites were investigated using various methods. The surface of the CNTs was modified using a linear alkyl chain in order to create a homogeneous CNT dispersion in the iPP matrix. When the CB content that was incorporated in the iPP matrix increased, the thermal and mechanical properties of the iPP/CB nanocomposites were enhanced. Additionally these enhancements in the properties were similarly induced by introducing a small amount of alkylated CNTs (a-CNTs). In contrast, the CB/a-CNT complex filler was more effective for the iPP nanocomposites than the CB or a-CNT single filler in terms of the thermal stability and the electrical properties. However, the mechanical properties of the CB/a-CNT complex filler incorporated iPP nanocomposites were poorer than the only a-CNT incorporated iPP nanocomposites. Additionally, the complex filler did not overcome the nucleation behavior of the a-CNTs in the re-crystallization of iPP.
Journal of Nanoscience and Nanotechnology 07/2011; 11(7):5928-33. DOI:10.1166/jnn.2011.4375 · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This short Perspective conveys to the general reader of Macromolecules basic approaches of materials science of polymeric membranes for gas and vapor separation. The relations between the polymer structure and transport properties of rubbery and glassy membrane materials are considered. On the basis of acquired information, several methods for quantitative prediction of permeability were developed, and their comparative analysis is given in the Perspective. The past decade was marked by the appearance of a number of novel interesting membrane materials, which will be briefly described in the text. In conclusion, novel approaches for achieving highly permeable and permselective materials (e.g., mixed matrix membranes) will be considered as well as several relevant but not solved so far problems of membrane gas separation.
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