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901.
K. Dinesh Kumar Andy H. Tsou Anil K. Bhowmick 《Journal of Polymer Science.Polymer Physics》2010,48(9):972-982
The effects of change in surface energy and bulk viscoelastic properties on the autohesive tack strength of brominated isobutylene‐co‐p‐methylstyrene (BIMS) rubber have been investigated by the addition of hydrocarbon resin (HCR) tackifier and maleated hydrocarbon resin (MA‐g‐HCR) tackifier. The addition of compatible HCR tackifier results in a reasonable increment in the tack strength of BIMS rubber by modifying only the bulk viscoelastic properties (compliance, entanglement molecular weight, relaxation time, self‐diffusion, and monomer friction coefficient values) of BIMS rubber to perform better during the course of bonding and debonding steps of the peel test. Incorporation of MA‐g‐HCR tackifier (containing 5–20 wt % of grafted maleic anhydride) steadily increases the tack strength of BIMS rubber further by precisely modifying both the surface energy and bulk viscoelastic properties to perform much better in the bonding and debonding steps. However, beyond 20 wt % of grafted maleic anhydride in the HCR tackifier, the tack strength starts decreasing due to the incompatibility between the blend components, and hence, the bulk viscoelastic properties required for bond formation are severely retarded by the interrelated reinforcing effect and the phase separation effect of the brittle MA‐g‐HCR tackifier in the BIMS rubber. Hence, the polar groups in a tackifier will contribute to significant enhancement of autohesive tack strength only if the bulk viscoelastic property of the rubber‐tackifier blend is favorable for bond formation and bond separation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 972–982, 2010 相似文献
902.
P. S. Anjana V. Deepu S. Uma P. Mohanan J. Philip M. T. Sebastian 《Journal of Polymer Science.Polymer Physics》2010,48(9):998-1008
Cerium oxide‐filled high density polyethylene (HDPE) composites for microwave substrate applications were prepared by sigma‐blend technique. The HDPE was used as the matrix and the dispersion of CeO2 in the composite was varied up to 0.5 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The variations of thermal conductivity (keff), coefficient of thermal expansion (αc) and Vicker's microhardness with the volume fraction of the filler were also measured. The relative permittivity (εeff) and dielectric loss (tan δ) were found to increase with increase in CeO2 content. For 0.4 volume fraction loading of the ceramic, the composite had εeff = 5.7, tan δ = 0.0068 (at 7 GHz), keff = 2.6 W/m °C, αc = 98.5 ppm/°C, Vicker's microhardness of 18 kg/mm2 and tensile strength of 14.6 MPa. Different theoretical approaches have been used to predict the effective permittivity, thermal conductivity, and coefficient of thermal expansion of composite systems and the results were compared with the experimental data. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 998–1008, 2010 相似文献
903.
904.
905.
Shaikh A. Ali N. Y. Abu‐Thabit Hasan A. Al‐Muallem 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5693-5703
The zwitterionic monomer, ethyl 3‐(N,N‐diallylammonio)propanephosphonate, was cyclopolymerized in aqueous solutions using t‐butylhydroperoxide or ammonium persulfate as initiators to afford a polyphosphonobetaine (PPB). The protonation of P(?O)OEtO– and deprotonation of ? NH+ groups in PPB by HCl and NaOH, gave the corresponding cationic polyphosphononic acid (CPP) and anionic polyphosphonate (APP). The presence of two pH‐responsive functionalities in APP has led to establish the equilibria: APP ? PPB ? CPP, the position of which very much dictates the viscosity behavior of its aqueous solution. The PPB demonstrated “antipolyelectrolyte” viscosity behavior; however, in contrast to many polycarbo‐ and polysulfo‐betaines, it was found to be soluble in salt‐free water as well as in salt‐added solutions. Basicity constant (K1) of the amine group in APP, as determined by potentiometric technique, were found to be “apparent,” and as such followed the modified Henderson‐Hasselbalch equation. The study demonstrated a correlation between the basicity constants and viscosity values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
906.
Lidia Jasinska Cor E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5907-5915
A new experimental approach for preparing biobased, water‐soluble polyesters (PEs) via titanium(IV) n‐butoxide‐catalyzed bulk polycondensation is presented. In the described method polymers were obtained from isosorbide, maleic anhydride and poly(ethylene glycol) (PEG). The chemical structure of the synthesized PEs was confirmed using 2D NMR spectroscopy and by titration methods. Careful analysis of 2D NMR spectra viz. correlation spectra (COSY), heteronuclear single quantum correlation spectra (HSQC) and heteronuclear multiple‐bond correlation spectra (HMBC) allowed to accomplish the complete proton assignment of isosorbide, PEG, and unsaturated acid residues in the PEs. Moreover, by using NMR spectroscopy the transformation of maleic anhydride into fumaric acid ester and the absence of maleic acid ester units in the final polymer were proven. However, during polycondensation part of the unsaturated bonds has reacted in a Michael addition with isosorbide or PEG. Gel permeation chromatography measurements revealed that the unsaturated PEs have Mn values in the range 3000–5000 g/mol. These PEs, with a low content of carboxylic acid end groups, exhibited sufficient thermal resistance for practical applications, for example, as free radical curable coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
907.
Wen Wu Sun Shi Rong Li Hong Zhou Dr. Zhi Quan Pan Dr. Qi Mao Huang Xue Lei Hu 《无机化学与普通化学杂志》2010,636(7):1386-1391
A new dumbbell‐type 4,4′‐bipy‐bridged dinuclear copper(II) complex, [Cu2(4,4′‐bipy)L2(H2O)2](ClO4)4 · 8CH3OH · 10H2O, where L = 1‐[bis(3‐aminopropyl)amino]‐2‐ propanol and bipy = bipyridine, has been synthesized and characterized, X‐ray crystallographic analysis shows that the [Cu2(4,4′‐bipy)L2(H2O)2]4+ cations and water molecules generate layer structures extending parallel to bc planes through hydrogen bonding interactions of O–H ··· O and C–H ··· O. The layers are also connected by hydrogen bonding interactions involving methanol, water, and perchlorate anions. These interactions lead to the formation of rectangular channels of 12.3 Å × 6.0 Å along the crystallographic c axis. Perchlorate anions fill in each channel in a sandwich‐like packing mode, they are joined with the adjacent layers by water heptamers. Magnetic susceptibility measurements show that the magnetic exchange interaction is weak although it has a regular π‐type electron transfer pathway. Furthermore, the electrochemical and thermogravimetric properties of the complex were also investigated. 相似文献
908.
The reactions of Ln(NO3)3 with 1,4‐phenylenediacetic acid (H2PDA) under hydrothermal conditions produced two isostructural lanthanide coordination polymers with the empirical formula [Ln2(PDA)3(H2O)] · 2H2O [Ln = Nd ( 1 ), Sm ( 2 )]. Single‐crystal X‐ray diffraction analyses revealed that both contain one‐dimensionalmetal carboxylato chains, which are further connected by the–CH2C6H4CH2– spacers of PDA2– ligands to yield a three‐dimensional metal‐organic framework. Magnetic susceptibilities of 1 and 2 were measured. The experimental χmT value of both compounds decreases continuously with decreasing temperature over the whole temperature range. The best least‐squares fit of the experimental data of 1 to a theoretical equation in the temperature range of 70–300 K gives the zero‐field splitting parameter Δ = 2.21 cm–1 and the magnetic interaction between the NdIII ions 2zJ′ = –1.97 cm–1, which indicates the presence of antiferromagnetic interaction between the NdIII ions. The experimental χmT value of 2 at 2 K is much smaller than the expected value for two free SmIII ions (6H5/2, g = 2/7) in the ground state, indicating that an antiferromagnetic interaction possibly exists between SmIII ions at low temperature. Fitting the magnetic data of 2 above 110 K based on an equation deduced from the SmIII ion in a monomeric system with free‐ion approximation gave a spin‐orbit coupling parameter λ = 192(2) cm–1 相似文献
909.
Powder samples and single crystals of the borides M0.5Ru6.5B3 (M = Cr, Mn, Co, Ni) were synthesized by arc‐melting the elements in a water‐cooled copper crucible under argon. The new phases were structurally characterized by single‐crystal and powder X‐ray diffraction as well as EDX‐Analyses. They crystallize in the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z = 2) and a pronounced site preferential M/Ru substitution is observed. Magnetic properties of the compounds were investigated and Pauli paramagnetism was observed in all cases. However, a strong temperature dependency is subsequently observed in Mn0.5Ru6.5B3 below 250 K, but no hint of magnetic ordering was found. 相似文献
910.
Reaction of iron(II) thiocyanate with 4,4‐bipyridine (bipy) in methanol leads to the formation of three new solvates of different composition depending on the reaction conditions: At room temperature two new ligand‐rich 1:2 (1:2 = ratio between metal and N‐donor ligand) polymorphic forms [Fe(NCS)2(bipy)2 · 2MeOH]n ( 1I ) and [Fe(NCS)2(bipy)(MeOH)2 · (bipy)]n ( 1II ) are obtained, whereas solvothermal conditions leads to the formation of the new ligand‐deficient 1:1 compound [{Fe(NCS)2(bipy)(MeOH)}2]n ( 2 ). All crystal structures were determined by X‐ray single crystal structure analysis. In the crystal structure of modification 1I the metal atoms are coordinated by four bridging bipy ligands, which connect them into layers. The methanol molecules occupy voids in the structure. Compared to 1I in modification 1II the crystal structure contains of linear Fe–bipy–Fe chains, which are further connected by hydrogen bonds between coordinating MeOH and noncoordinated bipy ligands into layers. The ligand‐deficient 1:1 compound 2 shows a completely different coordination topology with linear Fe–bipy–Fe chains, which are connected by coordinating methanol molecules into double‐chains. In all compounds the thiocyanato anions are terminal N‐bonded to the metal atoms. Investigation of the thermal behavior of compound 1I shows a two‐step decomposition, in which ligand‐deficient intermediates are formed. Magnetic measurements on 1I reveal Curie–Weiss paramagnetism with increasing antiferromagnetic interactions on cooling. 相似文献