Nanocomposites kinetics

H. Chen, D. F. Schmidt, M. Pitsikalis, N. Hadjichristidis, Y. Zhang, U. Wiesner, and E. P. Giannelis. Poly(styrene-block-isoprene) nanocomposites kinetics of intercalation and effects of copolymer on intercalation behaviors. Journal of Polymer Science, Part B Polymer Physics, 41 24 (2003), 3264-3271. 

Chen H, Schmidt DF, Pitsikalis M, Hadjichristidis N, Zhang Y, Wiesner U, Giannelis IP (2003) Poly(styrene- /ock-isoprene) nanocomposites kinetics of intercalation and effects of copolymer on intercalation behavior. J Polym Sci Polym Phys Ed 41 3264-3271 Mitchell CA, Krishnamoorti R (2002) Rheological properties of diblock copolymerdayered-silicate nanocomposites. J Polym Sci Polym Phys Ed 40 1434-1443... 

They have studied the properties of NR-epoxidized natural rubber (ENR) blend nanocomposites also. Vulcanization kinetics of natural mbber-based nanocomposite was also smdied. The effect of different nanoclays on the properties of NR-based nanocomposite was studied. The tensile properties of different nanocomposites are shown in Figure 2.7 [33]. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

The enzymatic activities of intercalated GOx-AM P layered nanocomposites at various pH values and temperatures were compared with the native enzyme in aqueous solution. In both cases, characteristic linear plots consistent with Michalis-Menton kinetics were obtained. The Lineweaver-Burk plots indicated that the reaction rates (Vmax) for free and intercalated GOx (3.3 and 4.0 pM min 1 respectively), were comparable, suggesting that the turnover rate at substrate saturation was only marginally influenced by entrapment between the re-assembled organoclay sheets. However, the dissociation constant (Km) associated with the activity of the enzyme was higher for intercalated GOx (6.63 mM) compared to native GOx (2.94 mM), suggesting... 

The kinetics of PAA, synthesized from 4,4 -oxydianiline and pyromellitic dianhydride, solid-state imidization both in filler absence and with addition of 2 phr Na+-montmorillonite was studied [1], The nanofiller was treated by solution of P-phenylenediamine in HC1 and then washed by de-ionized water to ensure a complete removal of chloride ions. The conversion (imidization) degree Q was determined as a function of reaction duration t with the aid of Fourier transformation of IR-spectra bands 726 and 1014 cm 1. The samples for FTIR study were obtained by spin-coating of PAA/Na+-montmorillonite mixture solution in N,N-dimethylacetamide on KBr disks, which then were dried in vacuum for 48 h at 303 K. It was shown, that the used in paper [1] method gives exfoliated nanocomposites. The other details of nanocomposites polyimid/Na+-montmorillonite synthesis and study in paper [1] were adduced. The solid-state imidization process was made at four temperatures 7) 423, 473, 503 and 523 K. 

Harmer and co-workers996,997 tested various Nafion-based samples in the dimerization of a-methylstyrene to form isomeric pentenes and a cyclic dimer, which are of industrial interest 13% and 40% Nafion-silica nanocomposites exhibited near-complete conversion and gave the cyclic dimer 300 with high selectivity [Eq. (5.360)], whereas compound 299a was the main product over Nafion NR50. In sharp contrast, isomeric pentenes 299 could be obtained in a continuous process (86% selectivity at conversion >95%). Similar findings were reported with Nafion immobilized in MCM-41 mesoporous silica. In kinetic studies, 13% Nafion-silica and the catalyst with... 

This kinetically dependent mechanism provides a means to develop a nanocomposite microstructure with the particles (or the majority of the particles) occluded within the matrix grains. On the other hand, occlusion can be prevented, for the most part, if glass-forming impurity elements are not introduced into the material during the processing stage. As we will see in the next section, the position of the particles (i.e. occluded or at grain boundaries) can influence the microstructurally dependent properties of nanocomposites. 

However, during long exposures to medium-temperature operating conditions, e.g. 1000°C, spinel formation is certainly expected. Wang etal.60 demonstrated this for the Ni-alumina system, showing the diffusion of Ni atoms to the free surface of the nanocomposite, followed by the formation of a nickel spinel surface coating which then limits the kinetics of subsequent oxidation. In this case the formation of a spinel surface layer may be beneficial to mechanical properties, since the reaction results in a volume increase, and the formation of compressive residual stresses. An analogous behavior was reported for ceramic particle nanocomposites, where oxidation of SiC particles results in an increase in volume and compressive residual stresses.61... 

Bourbigot, S., Gilman, J. W., and Wilkie, C. A. Kinetic analysis of the thermal degradation of polysty-rene-montmorillonite nanocomposite, Polym. Degrad. Stab. (2004), 84, 483 -92. 

One parameter, the kinetic energy of bovine spermatozoa motion (arbitrary units) in a viscous medium (standard cryo-protecting medium after a freeze-thaw cycle) was chosen to estimate bio-activity (Figure 2). Data corresponding to the admixture of nanocomposites (l)-(4) from Table 1 were measured using DLS in compared with the control cell suspension, and averaged over a wide concentration range of nanocomposite admixture. 

The picture becomes more informative if kinetic energy is referenced to the amount of sugar adsorbed on the nanocomposite surface. 

As mentioned earlier, polymerization techniques can also be used in the presence of nanotubes for preparation of polymer/CNT nanocomposite materials. In these, in-situ radical polymerization techniques of polymerization in the presence of CNT filler under or without applied ultrasound. Both new factors (presence of CNT and ultrasound) can affect reaction kinetics, stability of suspension or the size of prepared particles. For example, ultrasound waves can open C=C bond of monomer, which starts polymerization initiation. Thus vinyl monomers (styrene, methyl methacrylate or vinyl acetate) can be polymerized without addition of initiator, only by application of ultrasound. This is called sonochemical polymerization method (15,33,34). 

The 4th and 5th sessions of the Conference were held on October 5 at the Emanuel Institute of Biochemical Physics. The 4th session included seven reports. Dr. G.E. Zaikov presented the information about the latest achievements on reduction of inflammability of polymer materials and the use of nanocomposites as antipyrenes (substances that reduce the inflammability of polymer materials) Dr. A.A. Popov reported on the kinetics of destruction of strained polymers (strained molecules reactivity). The structural and dynamic parameters of interfacial layers in filled polymers were the subject of the report by A.L. Kovarskii and... 

The kinetics of 4-nitrophenol reduction in presence of microgel-metal nanocomposite particles was studied by UV/Vis spectroscopy. Figure 9 shows the UV spectra for the reduction of 4-nitrophenol measured at different times. For a typical measurement, successive decrease of peak intensity at 400 nm with time can be utilized to obtain the rate constant [59, 72, 73]. This peak is attributed due to the presence of 4-nitrophenate ions in the system. The formation of 4-nitrophenate ions... 

Sneddon s group investigated AB dehydrogenation in the ionic liquid l-butyl-3-methylimidazolium chloride (bmimCl) with an AB content of 50% [110]. Because of the low solubility of AB in bmimCl, one can assume that this system was essentially heterogeneous in nature. Similarly to the solid nanocomposites the change in the reaction environment induces several positive effects on the A B decomposition, such as an increase in the reaction kinetics, the absence of an induction period, a strong reduction in the borazine emissions, and with 1.6 equiv of H 2 at 98 °C in contrast to... 

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