Polymer–silica hybrids obtained by microemulsion polymerization

The styrene (St), butyl acrylate (BuA), and methyl methacrylate (MMA) polymerization in microemulsion in the presence of sodium dodecylsulfate is studied. This process is conducted in the presence of some comonomers having groups that can participate in sol–gel processes: 3(trimethyloxysilyl) propyl methacrylate (MPTS), triethoxy vinylsilane (VTES), and a comonomer with a sulfate group, styrene sodium sulfonate (StSO₃Na). It has been observed that stabile latexes are obtained by radical polymerization at pH = 7, followed by a sol–gel process in the presence of ammonia. Latex particles sizes and zeta potential grow with MTPS concentration and in StSO₃Na presence. VTES effect depends on its reactivity in St, MMA, and BuA copolymerization. Glass transition temperature and thermal decomposing temperature are influences by functional comonomer concentration and chemical structure. The Fourier transform infrared spectrum and inorganic residue growth after organic part thermal decomposition shows the presence of silica in obtained latexes.     

Metal-template-directed synthesis of diphosphorus compounds through intramolecular phosphinidene additions

Heating the nonchelating cis-bis-7-phosphanorbornadiene-[Mo(CO)4] complex (13) results in the thermal decomposition of one of the 7-phosphanorbornadiene groups. The phosphinidene thus generated adds intramolecularly to a C=C bond of the other ligand to give the novel diphosphorus complex 14. This reaction constitutes a metal-template-directed synthesis. Likewise, the intramolecular phosphinidene addition to the C=C bond of a Mo-phospholene ligand affords the diphos complex 18. Its crystal structure exhibits an extremely small P-Mo-P bite-angle for a five-membered chelate ring. The similar intramolecular 1,2-addition to a C=C bond of a phosphole ligand gives a highly strained, unstable intermediate product. Scission of its P-Mo bond generates a free coordination site, which is then occupied by either CO or a phosphole to yield complexes 22 and 23, respectively. The analogous intermolecular addition of [PhPW(CO)5] to a [phosphole-W(CO)5] complex gives the di-[W(CO)5] complexed adduct 28. The directing effect of the metal on the intra- and intermolecular additions is discussed.     

Loss of phosphorous in silica-phosphate sol-gel films

Phosphosilicate films with 90%SiO₂-10%P₂O₅ molar composition, derived from tetraethoxysilane as SiO₂ precursor and triethylphosphate, triethylphosphite or phosphoric acid as P₂O₅ precursors were prepared using the sol-gel method. The films were deposited on glass and ITO coated glass supports. The influence of the type of P₂O₅ precursor, type of substrate and of the thermal treatment (200, 300 and 500°C) on their structure and properties was studied. By spectroellipsometric and XPS measurements the high vaporization of the phosphorous during the densification of the films by thermal treatment was noticed when alkoxide were used, underlying that the mentioned precursors are not recommended for thin phosphosilicate films preparation. The phosphoric acid that forms chemical bond with silica network during the sol-gel process lead to better incorporation of P in the silica network as compared to the P-alkoxides.     

Transport numbers from hydrogen concentration cells over different oxides under oxidising and reducing conditions

Partial hydrogen ion conductivity in acceptor doped CaTiO(3), BaCeO(3) and ZrO(2) and nominally undoped BaTiO(3) and TiO(2) has been investigated by transport number measurements using the hydrogen concentration cell/EMF method in wet atmospheres as a function of pO(2)(10(-20)-1 atm) at 800 or 1000 [degree]C. All oxides investigated, except ZrO(2), show minor proton conductivity in oxidising atmospheres. Earlier indications of apparent negative charge transport by hydrogen under reducing conditions and high temperatures in SrTiO(3) samples have been reproduced for all the investigated oxides including ZrO(2).     

Individual equivalent conductances of the major ions in seawater

A radioactive tracer method has been used to determine the trnasference numbers of eight major ions in seawater of salinity 38.4 g-kg ^–1 at 25°C. Data are presented for Na⁺, K⁺, Ca ²⁺ , and Mg ²⁺ cations and Cl^–, Br^–, SO ₄ ^2– , and HCO ₃ ^– anions, which contribute to the overall electrical conductance by more than 99%. The results have been checked by electrophoretic migrations on esters of cellulose strips providing independent values of the ratios of ionic mobilities to be compared to previous estimations. Through the individual ionic contributions to the electrical conductance, a method for calculating seawater density is proposed; this method is based on a nine-constitutents seawater model in which relative ionic concentrations can deviate from that of standard seawater.     

Docking of protein-protein complexes on the basis of highly ambiguous intermolecular distance restraints derived from 1H/15N chemical shift mapping and backbone 15N-1H residual dipolar couplings using conjoined rigid body/torsion angle dynamics

A simple and reliable method for docking protein-protein complexes using (1)H(N)/(15)N chemical shift mapping and backbone (15)N-(1)H residual dipolar couplings is presented and illustrated with three complexes (EIN-HPr, IIA(Glc)-HPr, and IIA(Mtl)-HPr) of known structure. The (1)H(N)/(15)N chemical shift mapping data are transformed into a set of highly ambiguous, intermolecular distance restraints (comprising between 400 and 3000 individual distances) with translational and some degree of orientational information content, while the dipolar couplings provide information on relative protein-protein orientation. The optimization protocol employs conjoined rigid body/torsion angle dynamics in simulated annealing calculations. The target function also comprises three nonbonded interactions terms: a van der Waals repulsion term to prevent atomic overlap, a radius of gyration term (E(rgyr)) to avoid expansion at the protein-protein interface, and a torsion angle database potential of mean force to bias interfacial side chain conformations toward physically allowed rotamers. For the EIN-HPr and IIA(Glc)-HPr complexes, all structures satisfying the experimental restraints (i.e., both the ambiguous intermolecular distance restraints and the dipolar couplings) converge to a single cluster with mean backbone coordinate accuracies of 0.7-1.5 A. For the IIA(Mtl)-HPr complex, twofold degeneracy remains, and the structures cluster into two distinct solutions differing by a 180 degrees rotation about the z axis of the alignment tensor. The correct and incorrect solutions which have mean backbone coordinate accuracies of approximately 0.5 and approximately 10.5 A, respectively, can readily be distinguished using a variety of criteria: (a) examination of the overall (1)H(N)/(15)N chemical shift perturbation map (because the incorrect cluster predicts the presence of residues at the interface that experience only minimal chemical shift perturbations; this information is readily incorporated into the calculations in the form of ambiguous intermolecular repulsion restraints); (b) back-calculation of dipolar couplings on the basis of molecular shape; or (c) the E(rgyr) distribution which, because of its global nature, directly reflects the interfacial packing quality. This methodology should be particularly useful for high throughput, NMR-based, structural proteomics.     

Strained, stable 2-aza-1-phosphabicyclo[n.1.0]alkane and -alkene Fe(CO)4 complexes with dynamic phosphinidene behavior

The synthesis of highly strained bicyclic phosphirane and phosphirene iron-tetracarbonyl complexes, that is, complexes with 2-aza-1-phosphabicyclo[n.1.0]alkanes and -alkenes (n = 3-5), is explored by using intramolecular cycloaddition of an in situ generated electrophilic phosphinidene complex, [R(iPr)NP=Fe(CO)(4)], to its C=C- and C[triple chemical bond]C-containing R substituent. Saturated bicyclic complexes 7 a-c with n = 4-2 are remarkably stable, as illustrated by the X-ray crystal structure for 7 b (n=3), yet all readily undergo retroaddition to react with phenylacetylene. Shuttling of the phosphinidene iron complex between two equivalent C=C groups is demonstrated for a 1-butene-substituted 2-aza-1-phosphabicyclo[3.1.0]hexane by selective (1)H NMR magnetization transfer from the phosphirane protons to the olefinic protons. Even the more strained unsaturated bicycles 17 a,b (n = 4,3) are surprisingly stable as illustrated by the X-ray crystal structure for 17 a (n = 4), but the smaller phosphabicyclo[3.1.0]hex-5-ene (17 c, n = 2) dimerizes to tricyclic 19 with a unique ten-membered heterocyclic ring; an X-ray crystal structure is reported. Like their saturated analogues also the bicyclic phosphirenes readily undergo retroaddition as shown by the reaction of their phosphinidene iron moiety with phenylacetylene.     

Fuzzy modeling applied to optical and surface properties of a ferrocenylsiloxane polyamide solution

A fuzzy model was designed to predict changes in surface tension and maximum absorbance due to self-assembly in a DMF solution of poly{1,1′-ferrocene-diamide-[1,3-bis(propylene) tetramethyl-disiloxane} as a function of temperature and concentration. The building of fuzzy rule-based inference systems appears as a grey-box because it allows interpretation of the knowledge contained in the model as well as its improvement with a-priori knowledge. The method provides accurate results and increases the efficiency of utilizing the available information in the model. Small mean squared errors (0.0064 for absorbance and 0.79 for surface tension) and strong correlations between experiment and simulated results (0.93 and 0.97, respectively) were found during model validation. The results showed that it is feasible to apply a Mamdani fuzzy inference system to the estimation of optical and surface properties of a ferrocenylsiloxane polyamide solution.     

PIXE and PIGE assessment of in vivo elemental and physical changes of a composite from a dental filling

Simultaneous particle‐induced x‐ray emission (PIXE) and particle‐induced gamma‐ray emission (PIGE) measurements in the 0–270 keV range with a low‐energy hyperpure Ge detector have been performed on the outer surface and on an inner section of a dental composite filling extracted from a patient. The biomaterial has been identified as the fluorine‐releasing Tetric Ceram dental composite. Compared to the native material, the dental filling evidenced changes occurring during the in vivo oral use. These included mainly Cl and K accumulation and loss of Zr, Ba, Yb (by PIXE), and F (in the PIGE region). The changes were similar at the surface and inside of the dental filling for most of the above elements, indicating an unexpectedly high permeability of the material, maybe due to microscopic bulk fracture of the dental composite filling throughout its use. The PIGE spectra detected also Al and traces of Hf and Sm possibly associated with Zr and Yb. Changes in the ratio of the L lines of Yb and in the ratio of the 110‐ and 197‐keV lines of F evidenced alterations in the matrix physical properties of the composite, associated with factors such as surface roughening by wear, grain size decrease by slow dissolution, and compositional variations. Further studies are needed to gain a deeper insight into the complex changes taking place in a dental composite filling. Copyright © 2009 John Wiley & Sons, Ltd.