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51.
K. H. Wu P. H. Chen C. C. Yang W. D. Ho C. I. Liu 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):926-935
Hybrid coatings based on organically modified silicate‐Ni0.5Zn0.5Fe2O4/polyaniline were synthesized through a sol–gel technique with different NiZn ferrite/polyaniline weight ratio (1/1, 1/2, 1/5). These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection and to act as infrared stealth coatings. The effects induced by the NiZn ferrite/polyaniline hybrids on the chain dynamic, ferromagnetic behavior, infrared stealth, and anticorrosion performances of the coated samples were investigated. The rotating‐frame spin‐lattice relaxation times and scale of the spin‐diffusion path length indicated that the configuration of the hybrid films was highly cross‐linked and dense. The thermal extinction of the hybrid coatings increased with the increase in the polyaniline content. Potentio‐dynamic and salt‐spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 926–935, 2008 相似文献
52.
Theodore F. Baumann Ticora V. Jones Thomas Wilson Andrew P. Saab Robert S. Maxwell 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2589-2596
We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both the cross‐linker and filler within a polydimethylsiloxane (PDMS) polymer matrix. These polymer composites were prepared through the reaction of octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting of two pendant hepta(isobutyl)POSS molecules attached to a central octasilane‐POSS core, were also used in the fabrication of the PDMS composites. The chemical incorporation of these POSS cross‐linkers into the PDMS network was verified by solid‐state 1H magic angle spinning NMR. Based on dynamic mechanical analysis, the PDMS nanocomposites prepared with the octafunctional OS‐POSS cross‐linker exhibited enhanced mechanical properties relative to polymer systems prepared with the tetrafunctional TDSS cross‐linker at equivalent loading levels. The observed improvements in mechanical properties can be attributed to the increased dimensionality of the POSS cross‐linker. The PDMS elastomers synthesized from the larger super‐POSS molecule showed improved mechanical properties relative to both the TDSS and OS‐POSS composites due to the increased volume‐fraction of POSS filler in the polymer matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2589–2596, 2009 相似文献
53.
We report the first use of functionalized Ag2Se nanoparticles (NPs) as effective extracting probes for NPs-based liquid-phase microextraction (NPs-LPME) to analyze hydrophobic peptides and proteins from biological samples (urine and plasma) and soybean in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Surface modified functional groups such as octadecanethiol (ODT) and 11-mercaptoundecanoic acid (MUA) on Ag2Se NPs were found to play an important role for efficient extraction of peptides and proteins from test samples through hydrophobic interactions. The peptides can be efficiently extracted using functionalized Ag2Se NPs as extracting probes in the presence of high concentration of matrix interferences such as 4 M urea, 0.5% Triton X-100 and 3% NaCl. Ag2Se@ODT NPs have shown better extraction efficiency and detection sensitivity for peptides than Ag2Se@MUA NPs, bare Ag2Se NPs and conventional MALDI-MS. The LODs are 20-68 nM for valinomycin and 100-180 nM for gramicidin D using Ag2Se@ODT NPs-LPME in the MALDI-MS. The current approach is highly sensitive and the target analytes can be effectively isolated without sample loss and efficiently analyzed in MALDI-MS. 相似文献
54.
Accelerated thermal ageing studies on foamed condensation cured polysiloxane materials have been performed in support of life assessment and material replacement programmes. Two different types of filled hydrogen-blown and condensation cured polysiloxane foams were tested; commercial (RTV S5370), and an in-house formulated polysiloxane elastomer (Silfoam). Compression set properties were investigated using Thermomechanical (TMA) studies and compared against two separate longer term ageing trials carried out in air and in dry inert gas atmospheres using compression jigs. Isotherms measured from these studies were assessed using time-temperature (T/t) superposition. Acceleration factors were determined and fitted to Arrhenius kinetics. For both materials, the thermo-mechanical results were found to closely follow the longer term accelerated ageing trials. Comparison of the accelerated ageing data in dry nitrogen atmospheres against field trial results showed the accelerated ageing trends over predict, however the comparison is difficult as the field data suffer from significant component to component variability. Of the long term ageing trials reported here, those carried out in air deviate more significantly from field trials data compared to those carried out in dry nitrogen atmospheres. For field return samples, there is evidence for residual post-curing reactions influencing mechanical performance, which would accelerate compression set. Multiple quantum-NMR studies suggest that compression set is not associated with significant changes in net crosslink density, but that some degree of network rearrangement has occurred due to viscoelastic relaxation as well as bond breaking and forming processes, with possible post-curing reactions at early times. 相似文献
55.
Megan A. Cole Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2013,51(8):1749-1757
Polysiloxanes are commonly used in a myriad of applications, and the “click” nature of the thiol‐ene reaction is well suited for introducing alternative functionalities or for crosslinking these ubiquitous polymers. As such, understanding of the thiol‐ene reaction in the presence of silicones is valuable and would lead to enhanced methodologies for modification and crosslinking. Here, the thiol‐ene reaction kinetics were investigated in functionalized oligosiloxanes having varying degrees of thiol functionalization (SH), π–π interactions (from diphenyls, DP), and ene types (C?C). In the ene‐functionalized oligomers, π–π interactions were controlled through the use of dioctyl repeats (DO). The polymerization rate and rate‐limiting steps were determined for all systems containing an allyl‐functionalized oligomer, and rates ranging from 0.10 to 0.54 mol L?1 min?1 were seen. The rate‐limiting step varied with the oligomer composition; examples of rate‐limited propagation (5:3:2 C?C:DP:DO/1:1 SH:DP) or chain transfer (5:3:2 C?C:DP:DO/3:1 SH:DP) were found in addition to cases with similar reaction rate constants (5:2:3 C?C:DP:DO/1:1 SH:DP). None of the siloxanes were found to exhibit autoacceleration despite their relatively high viscosities. Instead, the allyl‐, vinyl‐, and acrylate‐functionalized siloxanes were all found to undergo unimolecular termination based on their high α scaling values (0.98, 0.95, and 0.82, respectively) in the relation Rp ∝ Riα. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
56.
Leandro E. Roth Enrique M. Valls Marcelo A. Villar 《Journal of polymer science. Part A, Polymer chemistry》2003,41(8):1099-1106
Model silicone networks obtained by curing linear poly(dimethylsiloxane) (PDMS) chains with end‐vinyl groups, (B2), with a polyfunctional silane‐terminated crosslinker of functionality f, (Af), through a hydrosilylation reaction have been widely used. In these networks, the principal characteristics of their ultimate molecular structure are strongly affected by the final extent of reaction reached during the crosslinking reaction. This work analyzes the effect of the initial concentration of the reactive end groups on the maximum attainable extent of reaction under normal bulk crosslinking conditions. This was accomplished by examining the reaction between linear B2 PDMS chains with difunctional and trifunctional silanes. The experimental results were fitted by an exponential equation to have an empirical equation able to predict the maximum extent of reaction to be obtained as a function of the initial concentration of reactive groups. Molecular parameters relevant to this study, such as the degree of polymerization, the weight‐average molecular weight for the A2 + B2 system, or the weight fraction of solubles for the A3 + B2 system, were calculated with a mean field theory (recursive approach). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1099–1106, 2003 相似文献
57.
Salman M. Saadeh Nizam M. El‐Ashgar Issa M. El‐Nahhal Mohamed M. Chehimi Jocelyne Maquet Florence Babonneau 《应用有机金属化学》2005,19(6):759-767
A porous, solid insoluble polysiloxane‐immobilized ligand system bearing pyrogallol active sites of the general formula P? (CH2)3? NH(CH2)3OC6H3(OH)2 (where P represents [Si? O]n siloxane network) has been prepared by the reaction of 3‐aminopropylpolysiloxane with 1,3‐dibromopropane followed by the reaction with pyrogallol. 13C CP‐MAS NMR and X‐ray photoelectron spectroscopy confirmed that the pyrogallol is chemically bonded to the siloxane backbone. Thermal analysis showed that the ligand system is stable under nitrogen at relatively high temperature. The polysiloxane–pyrogallol ligand system exhibits high potential for the uptake of the metal ions (Fe3+, Co2+, Ni2+ and Cu2+). Complexation of the pyrogallol ligand system for the metal ions at the optimum conditions was found to be in the order Fe3+ > Cu2+ > Ni2+ > Co2+. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
58.
Nihan Nugay Gabor Erdodi J. P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》2005,43(3):630-637
This article mainly concerns the synthesis of novel PD5/PDMS conetworks by the copolymerization of cyclic D5H and linear HO? PDMS? OH units, and the characterization of the product by DMTA, DSC, and TGA. The ultimate properties of the conetworks may be controlled by varying the relative composition of D5H and PDMS components. DMTA and DSC thermograms indicate compatibility between the PD5 and PDMS domains. Understanding of the polymer chemical transformations involved in conetwork formation combined with an analysis of DMTA and DSC thermograms led to a proposition of the microarchitecture of PD5/PDMS conetworks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 630–637, 2005 相似文献
59.
Ping‐Lin Kuo Wei‐Fu Chen Wuu‐Jyh Liang 《Journal of polymer science. Part A, Polymer chemistry》2005,43(15):3359-3367
A new class of proton‐conducting polymer was developed via the sol–gel process from amino‐containing organic–inorganic hybrids by the treatment of poly(allylamine) with 3‐glycidoxypropyltrimethoxysilane doped with ortho‐phosphoric acid. The polymer matrix contains many hydrophilic sites and consists of a double‐crosslinked framework of polysiloxane and amine/epoxide. Differential scanning calorimetry results suggest that hydrogen bonding or electrostatic forces are present between H3PO4 and the amine nitrogen, resulting in an increase in the glass‐transition temperature of the poly(allylamine) chain with an increasing P/N ratio. The 31P magic‐angle spinning NMR spectra indicate that three types of phosphate species are involved in the proton conduction, and the motional freedom of H3PO4 is increased with increasing P/N ratios. The conductivity above 80 °C does not drop off but increases instead. Under a dry atmosphere, a high conductivity of 10?3 S/cm at temperatures up to 130 °C has been achieved. The maximum activation energy obtained at P/N = 0.5 suggests that a transition of proton‐conducting behavior exits between Grotthus‐ and vehicle‐type mechanisms. The dependence of conductivity on relative humidity (RH) above 50% is smaller for H3PO4‐doped membranes compared with H3PO4‐free ones. These hybrid polymers have characteristics of low water content (23 wt %) and high conductivity (10?2 S/cm at 95% RH), making them promising candidates as electrolytes for fuel cells. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3359–3367, 2005 相似文献
60.
The research on developing a purification technology for Cr(Ⅵ) polluted water with high efficiency and the low energy consumption is crucial for achieving several Sustainable Development Goals (SDGs). In order to achieve these goals, Fe3O4@SiO2-APTMS nanocomposites were prepared by Fe3O4 nanoparticles modified with silica and 3-aminopropyltrimethoxysilane in the presence of ultrasonic irradiation. The nanocomposites were characterized by TEM, FT-IR, VSM, TGA, BET, XRD, XPS and these analytic results proved that the nanocomposites were successfully prepared. The influential factors of Fe3O4@SiO2-APTMS on Cr(Ⅵ) adsorption have been explored and better experimental conditions have been obtained. The adsorption isotherm conformed to the Freundlich model. Pseudo-second-order kinetic model provided a better correlation for the experimental data compared to other kinetic models. Thermodynamic parameters for adsorption indicated that the adsorption of Cr(Ⅵ) was a spontaneous process. It was speculated that the adsorption mechanism of this adsorbent includes redox, electrostatic adsorption and physical adsorption. In summary, the Fe3O4@SiO2-APTMS nanocomposites were of great significance to human health and the remediation of heavy ion pollution, contributing to achievement of the Sustainable Development Goals (SDGs), including SDG-3, SDG-6. 相似文献