Metal-containing initiator systems. V. Radical and cationic polymerizations with initiator systems of reduced nickel and chlorosilanes

The polymerizations of methyl methacrylate, styrene, and isobutyl vinyl ether with the binary systems of reduced nickel and chlorosilanes [(CH₃)_nSiCl_4?n, n = 0–3] have been investigated. It was found that these systems could act as both radical and cationic initiators, depending on the nature of vinyl monomers used. The kinetic investigations indicated that methyl methacrylate polymerized via a radical mechanism, and the initiating activity of chlorosilanes decreased in the following order: SiCl₄ > CH₃SiCl₃ > (CH₃)₂SiCl₂ > (CH₃)₃SiCl ? 0. Cationic initiations were observed in the polymerizations of styrene and isobutyl vinyl ether. In the latter case, the activity of chlorosilanes was in the following order: (CH₃)₃SiCl > (CH₃)₂SiCl₂ > CH₃SiCl₃ ? SiCl₄. From the results obtained, a possible mechanism of selective initiation with these systems is proposed and discussed.     

Structure-dependent photophysics studied in single molecules of polythiophene derivatives.

We report on the photophysical characterization at the single-molecule level of a graft copolymer consisting of a polythiophene backbone and long polystyrene branches. The presence of the branches prevents the polymer chain from forming a collapsed conformational state. The photophysical properties of the resulting solution-like conformation are studied by measuring single-molecule photobleaching dynamics, emission polarization anisotropy and emission spectra. The results are compared with those obtained on the same polythiophene derivative without the branches. It is found that the presence of the branches is a decisive factor in determining the photophysical properties of the polymers on the single-molecule level.     

Elastic and inelastic scattering of vector polarized deuterons from even samarium isotopes at 56 MeV

Differential cross sections and vector analyzing powers of deuteron elastic and inelastic scattering have been measured at 56 MeV over the whole range of the even samarium isotopes. Comprehensive analyses were performed with the optical model and the coupled-channels formalism. In the optical model analysis, calculations with a global parameter set could reproduce the experimental data only for the vibrational nuclei. The strong coupling approximation was applied assuming the ^{144, 148, 150}Sm to be harmonic vibrators and the ^152,154Sm symmetric rotators. The 2^λ (λ = 2, 3, 4, 6) pole deformation parameters were deduced from a systematic coupled-channels analysis. The transition strengths were extracted from the deformed optical potentials and compared with the corresponding electromagnetic ones. The transition rates for the rotational nuclei agreed with the electro-magnetic ones, but those for the vibrational nuclei gave the systematically smaller values. The latter fact was attributed to the difference between the proton and neutron transition matrix elements near the neutron-closed-shell nuclei. The ratios of the two matrix elements were obtained.     

Thermodynamics of surfactant-dye complex formation in aqueous solutions II. Sodium dodecyl sulfate and some azo oil dye systems

Spectrophotometric and thermodynamic investigations are reported of the interactions between anionic surfactant (sodium dodecyl sulfate) and six azo oil dyes (benzene azo naphthalene type) which have an amino group at 4-position of naphthalene. A pronounced spectral change in the dye solution occurs on addition of surfactant. For increasingly surfactant concentrations (below the CMC), the interaction between dye and surfactant is so sharp that the systems may be said to exhibit an isosbestic point; then a new absorption band appears at longer wavelengths. The spectral data can be quantitatively interpreted in terms of a complex formation. The equilibrium coefficients of the complex formation are determined at different temperatures. The thermodynamic parameters of the complex formations (the free energy change (G), enthalpy change (H) and change in entropy (S) are also calculated. The reaction of complex formation is exothermic (H negative).G is dependent on the hydrophobic nature andpKa of the dye. These complexes will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.With increasing amounts of complex, the infinite adsorption, the exhaustion and the rate constant of dyeing for nylon decrease.     

Nanoparticle-induced multi-functionalization of silicon: A plug and play approach

Here, we demonstrate a “plug and play” approach to achieve multi-functionalization of Si. In this approach, externally synthesized functional nanoparticles are introduced onto device quality Si wafers and the surface chemical bonds are manipulated. Sonochemically synthesized Fe₂O₃ nanoparticles are introduced onto Si from an alcohol suspension. On annealing this sample in ultra-high vacuum, the oxygen atoms change the bonding partner from Fe to Si and desorb as SiO at 750 °C. This results in the formation of nanoparticles of Fe on the surface and exhibits ferromagnetic behavior. Deposition of a thin layer (2 nm) of Si onto the sample containing the metallic Fe nanoparticles followed by annealing at 560 °C leads to optically active Si. Photoluminescence measurements show that this sample emits light at three different wavelengths, namely 1.57, 1.61 and 1.63 μm, when excited by He–Ne or Ar lasers. Oxidation of this material results in the formation of a selective capping layer of SiO₂. Thus we obtain multi-functional Si in an “all in one” form and we believe that this approach is universal.     

4-(t-butylthio)-3-buten-2-one. Synthon for α,β- and α,β,γ,δ-unsaturated aldehyde synthesis

A convenient synthesis of α,β- and α,β,γ,δ-unsaturated aldehydes using readily accessible 4-(t-butylthio)-3-buten-2-one as synthon was described.     

Computations and Stability of the Fukui Invariant

T. Fukui introduced an invariant for the blow-analytic equivalence of real singularities. For a nondegenerate analytic function (germ) f, he discovered a formula for computing the one-dimensional invariant, denoted by A(f) := A ₁(f). We find a formula for A(f) for any f (real or complex, degenerate or not). We then define, and characterise, various notions of stability of A(f), using the formula. For real analytic f, the Fukui invariant with sign is defined, and computed by a similar formula. In the case where f is an analytic function of two complex variables, A(f) can also be computed using the tree-model of f.