Stereospecific Synthesis of Endo-6-Aryl-2-Oxobicyclo [3.3.1]Nonanes

Two alternate synthetic routes to endo-6-aryl-2-oxobicyclo 3.3.1 nonan [3a-d] by sterespecific catalytic hydrogenetion of the easily accessible 6-arylbicyclo 3.3.1 nona-3,6-dien-2-ones [2a-d], and regioselective oomologation of endo-2-aryl-6-oxobicycle 3.2.1 octanes [4a-d] are described.     

Conducting polymer “nanogates” – Controllable diffusivities in thin films of novel tether-containing sulfonated polythiophenes

We describe a nanoscale gating effect by an atypical tether-containing polythiophene, [poly(thiophene-3-carboxylic acid 2-(2-(2-(2-ethoxy-ethoxymethyl sulfonate)-ethoxy)-ethoxy)-amide], referred to as poly(TP-OEG-SO₄). Cyclic voltammetry data permitted us to calculate liquid-phase ion diffusivities in the polymer as a function of its oxidation state. Diffusivities are more than 350 times higher in the oxidized state versus the reduced state. As a control, poly 3′,4′-dimethyl-[2,2′;5′,2″] terthiophene (DMPT) was synthesized and characterized. On comparing both polymers in the reduced state, we find diffusivities in poly(TP-OEG-SO₄) to be more than 4500 times lower than in poly(DMPT). To explain this behavior, we propose a model that features a charge-balancing mechanism by the sulfonate tethers in poly(TP-OEG-SO₄), which causes nanoporous regions around the polymer main chains to be opened and closed, leading to the large observed differences in diffusivities. These data suggest that the polymer poly(TP-OEG-SO₄) is evidently able to act as a reversible “nanogate” with an open pore structure when oxidized, and a closed one when reduced.     

Investigation of short-time particle dynamics near an interface in the presence of nonadsorbed macro-ions

The optical technique of total internal reflection microscopy was used to study the normal Brownian motion of a single colloidal particle near an interface. The measurements were made using a recently developed technique in which the diffusion coefficient was determined by the variance of the short-time (Deltat --> 0) motion of the particle. Experiments were performed in solutions containing either silica nanospheres or clay platelets (Laponite RD) to investigate the effect of nonadsorbed material on the dynamics of near-contact particle motion. The change in the diffusion coefficient with separation distance between the particle and plate in solutions containing nonadsorbed macro-ions was well-described by the theory developed for simple fluids. These results suggest that, in dilute solutions of nonadsorbed material in which the bulk rheological properties remain similar to those of the pure fluid, the mobility and diffusion coefficient correction factors developed for simple fluids remain valid.     

Compatibility of tire elastomers using derivative heat flow traces in the glass transition region

Derivative heat flow curves give much more information about the phase heterogeneity of binary blends composed of NR, SBR and BR elastomers thanT _g. In blend compositions, the areas under the derivative heat flow curves appear to be an additive function of the concentration of elastomers in the case of incompatible blends (NR/BR, NR/SBR). They are less than additive for either a partially compatible blend (uncured SBR/BR) or a compatible blend (covulcanized SBR/BR). In the case of 60/40 SBR/BR blends, a DSC (T _0.5) reveals a singleT _g, in conformity with the earlier investigators, whereas the derivative heat flow curve shows two peaks (T _p) indicating incomplete homogenization of the phases. This is a new observation not mentioned in the published literature. Thus, derivative heat flow traces are likely to provide a unique tool to determine compatibility of elastomers. The study also reveals the importance of sample contact with the DSC pan in quantitative determinations.     

Characterization of isomeric elastomers using thermal analysis

Many of the isomers of polybutadiene and polyisoprene elastomers can be characterized by thermal analysis.T _g is sensitive to side chain units (1,2 or 3,4 structure) for both polymers. Crystallinity measurements can characterizecis andtrans isomers. DMA and DEA master curves provide an idea of the heterogeneity of the chain units from the width of the loss factor curves in theT _g region. Thermal and thermooxidative degradation, as followed by DSC and DTG, can differentiate specific natural and synthetic isomers of polyisoprenes in raw and vulcanized states.     

Sensitivity of PSA process performance to input variables

Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.     

Separation and recovery of intact gold-virus complex by agarose electrophoresis and electroelution: application to the purification of cowpea mosaic virus and colloidal gold complex

Colloidal gold has been coupled to a mutant cowpea mosaic virus (CPMV), which contains 60 cysteine residues on the surface. A purification process was developed to separate the gold-containing viral nanoblocks (VNBs) from the free gold. Agarose electrophoresis was utilized to separate the mixture followed by electroelution of the desired sample to recover the intact virus. Mobility of Au-VNB and free colloidal gold was facilitated by the addition of thioctic acid (TA). 30% of the gold-containing virus was recovered after electroelution as determined by absorbance measurements. Histogram analysis of transmission electron microscopy (TEM) images demonstrated the efficient separation of gold-containing virus from free gold. TEM and scanning electron microscopy (SEM) images indicated that the virus was recovered intact. Monodisperse spherical particles of nominal size of 45 nm were observed under SEM.     

Bis-salicylaldehyde-ethylenediamine as an analytical reagent

Summary The compound bis-salicylaldehyde-ethylenediamine was prepared by the condensation of salicylaldehyde with ethylenediamine. It was crystalline and quite stable. The solution of the compound in caustic alkali was used for the analytical reactions of various ions. Ions of Cu²⁺, Ni²⁺, Bi³⁺, Zn²⁺, Hg²⁺, Sb³⁺, Sn²⁺ and Ce⁴⁺ formed precipitates, while those of As³⁺ and Pd²⁺ gave slight turbidity and Fe²⁺, Pe³⁺, Co²⁺ gave colour reactions. Rest of the ions did not respond towards the reagent. The sensitivity of the reactions for Cu²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Ce⁴⁺, Co²⁺ and Sb³⁺ was high and their quantitative determinations are possible.

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Zusammenfassung Die Verbindung Bis-salicylaldehyd-äthylendiamin wurde durch Kondensation von Salicylaldehyd mit Äthylendiamin dargestellt. Sie ist kristallin und durchaus stabil. Die ätzalkalische Läsung dieser Verbindung wird zu analytischen Reaktionen mit verschiedenen Ionen benutzt. Die Ionen Cu²⁺, Ni²⁺, Bi³⁺, Zn²⁺, Hg²⁺, Sb³⁺, Sn²⁺ und Ce⁴⁺ ergeben Niederschläge, As³⁺ und Pd²⁺ geben eine geringe Trübung und Fe²⁺, Fe³⁺ sowie Co²⁺ liefern Farbreaktionen. Die übrigen Ionen sprechen auf das Reagens nicht an. Die Empfindlichkeit der Reaktionen mit Cu²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Ce⁴⁺, Co²⁺ und Sb³⁺ ist groß und eine quantitative Bestimmung dieser Ionen ist möglich.

     

Modelling adsorbent heterogeneity for adsorption from binary liquid mixtures

It is demonstrated that the detailed structure of the surface energy or selectivity distribution function is not critical to obtaining adequate analytical expressions for surface excess isotherms for adsorption from binary liquid mixtures on heterogeneous adsorbents. The gamma and the uniform selectivity distribution functions, which are very different in form, were successfully used in conjunction with the monolayer-pore filling model for adsorption on a homogeneous site to describe adsorption of various binary liquid mixtures on silica gel. Both models described the salient features of the surface characteristics of the silica gel.