Three difunctional low polarity acrylate monomers were synthesized in this *** purification, the obtained acrylates were then mixed with a co-monomer tricyclodecane dimethanol diacrylate(TDDA) to prepare their homopol...
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Three difunctional low polarity acrylate monomers were synthesized in this *** purification, the obtained acrylates were then mixed with a co-monomer tricyclodecane dimethanol diacrylate(TDDA) to prepare their homopolymers and copolymers by irradiating *** chemical structures of obtained symmetry acrylates (SA1, SA2 and SA3) were characterized by *** thermal degradation temperatures of the obtained films were tested by thermal gravimetric analysis (TGA).
Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed t...
Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed the quaternization of the polymer (PIp-b-PNMe2VP), and determined the degree of quaternization by conductometric titration. The surface tension experiment showed that the polymers are non-surface active in nature. The foam formation of the polymer solutions was also investigated with or without added salt. Almost no foam formation behavior was observed without added salt, while a little foam was observed in the presence of 1M NaCl. The critical micelle concentration (cmc) of the diblock copolymers with 3 different chain lengths was measured by the static light scattering method. The cmc values obtained in this study were much lower than the values obtained for anionic non-surface active diblock polymers studied previously. The hydrodynamic radii of the polymer micelle increased slightly in the presence of 1 M NaCl. The transmission electron microscopic images revealed spherical micelles in pure water. In the presence of salt, the cmc values increased as was the case for anionic polymers, which is unlike conventional surfactant systems but consistent with non-surface active anionic block copolymers. The microviscosity of the micelle core was evaluated using Coumarin-153 as a fluorescent anisotropy probe using steady-sate fluorescence depolarization. Non-surface activity has been proved to be universal for ionic amphiphilic block copolymers both for anionic and cationic. Hence, the origin of non-surface activity is not the charged state of water surface itself, but should be an image charge repulsion at the air/water interface.
Semiconducting hexathiapentacene (HTP) single–crystal nanowires were synthesized using a simple solution-phase route. Quartz Crystal Microbalance and complex resistance measurements were employed to investigate the s...
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Semiconducting hexathiapentacene (HTP) single–crystal nanowires were synthesized using a simple solution-phase route. Quartz Crystal Microbalance and complex resistance measurements were employed to investigate the sensing properties of an HTP nanowire to analytes including acid, amine, and hydrocarbon vapors. Cole-Cole plots (0.01Hz-4 MHz) of measured impedance spectra, modeled using equivalent circuits, were used to resolve the effects of adsorption and charge migration.
Semiconducting hexathiapentacene (HTP) single-crystal nanowires were synthesized using a simple solution-phase route. Quartz Crystal Microbalance and complex resistance measurements were employed to investigate the se...
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Giant permittivity at 1 MHz, which slightly changes with temperatures, is observed in a polymer composite. The dielectric spectroscopy demonstrates that the samples are electrically heterogeneous. The microstructure o...
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Giant permittivity at 1 MHz, which slightly changes with temperatures, is observed in a polymer composite. The dielectric spectroscopy demonstrates that the samples are electrically heterogeneous. The microstructure observation and the ingredient analysis evidence they self assemble the conducting cores surrounded by the insulating shells. The giant-dielectric phenomenon is therefore attributed to the percolation effect. The electrically heterogeneous microstructure with effective permittivity values about 10 000 can be fabricated by a simple solution casting process in air. The composite is an attractive option to the currently used printing dielectric and the future flexible electronics.
A theoretical model is developed for ferroelectric bilayers and multilayer heterostructures that employs a nonlinear Landau-Devonshire formalism coupled with a detailed analysis of the depolarizing fields arising from...
A theoretical model is developed for ferroelectric bilayers and multilayer heterostructures that employs a nonlinear Landau-Devonshire formalism coupled with a detailed analysis of the depolarizing fields arising from the polarization mismatch across interlayer interfaces and the electrical fields of localized space charges at such interfaces. We first present how space charges alter the free-energy curves of ferroelectrics and then proceed with a numerical analysis for heteroepitaxial (001) PbTiO3-SrTiO3 (PTO-STO) bilayers and (001) superlattice structures on (001) STO substrates. The switchable (ferroelectric) and nonswitchable (built-in) polarizations and the dielectric properties of PTO-STO bilayers and superlattices are calculated as a function of the planar space-charge density and the volume fraction of the PTO layer. Similar to the temperature dependence of a monolithic ferroelectric, there exists a critical volume fraction PTO below which the bilayer or the superlattice is in the paraelectric state. This critical volume fraction is strongly dependent on the density of trapped charges at the interlayer interfaces. For charge-free (001) PTO-STO heteroepitaxial bilayer and superlattices, the critical fraction is 0.40 for both constructs but increases to 0.6 and 0.72, for the bilayer and the superlattice, respectively, for a planar space-charge density of 0.05 C/m2. Furthermore, our results show that close to the vicinity of ferroelectric-paraelectric phase transition, there is a recovery in ferroelectric polarization. The dielectric-response calculations verify that there is sharp ferroelectric phase transformation for charge-free bilayers and superlattices whereas it is progressively smeared out with an increase in the charge density. Furthermore, our analysis shows that the dielectric constant of these multilayers at a given volume fraction of PTO decreases significantly in the presence of space charges.
The kinetics and the corresponding “atomic” processes of nucleation, growth and defect formation are simulated by alternating electric field controlled colloidal crystallization. Such a system allows us not only to ...
The kinetics and the corresponding “atomic” processes of nucleation, growth and defect formation are simulated by alternating electric field controlled colloidal crystallization. Such a system allows us not only to visualize some “atomic” details of nucleation, step dynamics, roughening transition, defect dynamics, but also for the first time to verify quantitatively the previous models published to describe the above processes. Based on the studies, some new knowledge on the initial stage of nucleation, multi step crystallization, etc., was generated. As the colloidal crystallization system displays the phase behaviors similar to normal crystalline materials, and the crystallization condition can be controlled easily and precisely, it can be foreseen that this approach will become a powerful tool to study the science and technology of crystallization.
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