Interactions between colloidal particles in polymer solutions: A density functional theory study

We present a density functional theory study of colloidal interactions in a concentrated polymer solution. The colloids are modeled as hard spheres and polymers are modeled as freely jointed tangent hard sphere chains. Our theoretical results for the polymer-mediated mean force between two dilute colloids are compared with recent simulation data for this model. Theory is shown to be in good agreement with simulation. We compute the colloid-colloid potential of mean force and the second virial coefficient, and analyze the behavior of these quantities as a function of the polymer solution density, the polymer chain length, and the colloid/polymer bead size ratio.     

Thermal behaviour of resorcinol-1,2-dichloroethane resin

Resorcinol-1,2-dichloroethane resin was prepared by Friedel-Craft polymerization from resorcinol and 1,2-dichloroethane. The resin sample was characterised by IR and UV spectra and the average molecular weight was determined by vapour pressure osmometry. Kinetic parameters from TG and DTA thermograms are reported.     

Equilibrium/nonequilibrium initial configurations in forward/reverse electron transfer within mixed-metal hemoglobin hybrids

In a protein-protein electron transfer (ET) photocycle, the "forward" ET reaction is initiated with the excited complex, [3DA], in an equilibrium ensemble of configurations, the majority of which exhibit less than the maximal ET matrix element. In contrast, the charge-separated intermediate complex is formed in a nonequilibrium set of configurations with maximal ET matrix elements and would be expected to return to the ground state with the largest rate constant possible unless conformational interconversion first "breaks the connection" and the complex converts to less-reactive substates. According to this analysis, the forward and back ET reactions should show a differential response to viscosity, and the latter could even show an increased rate constant under conditions which suppress departure from the reactive configuration(s). We now report that the viscosity dependences of forward and back ET rate constants for the photocycle within the [alpha2(Zn),beta2(Fe3+N3-)] mixed-metal hemoglobin hybrid at pH 7 show the anticipated behavior: kf decreases as viscosity increases, but, in sharp contrast, kb increases strongly.     

A new route for isoquinolines catalyzed by palladium

3-Bromopyridine-4-carbaldehyde is tethered with suitably electron withdrawing group substituted alkenes via Heck coupling followed by aldol reaction in dioxane at 150 °C under a catalytic system of Pd(OAc)₂/PPh₃/NaOAc to afford the corresponding isoquinolines in good yields.     

Poly-Schiff bases. I. Preparation of poly-Schiff bases from 4,4′-diacetyl diphenyl ether (DDE) with various diamines

Thermally stable and semiconducting poly-Schiff bases are synthesized by condensing 4,4′-diacetyl diphenyl ether with o-, m-, and p-phenylene diamines, benzidine, and ethylene diamine under different experimental conditions. These bases are insoluble in common organic solvents. They are characterized by infrared (IR) and viscosity measurements, thermal analysis, and the study of electricel properties at various temperatures. Variation of electrical conductivity σ with temperature followed the empirical relation σ = σ₀e^?E*/kT.     

Fingerprint analysis of Shankhpushpi for species discrimination by HPLC coupled with chemometric methods

Abstract

Shankhpushpi, traded in the Indian market is having different controversial botanical sources, that is, Convolvulus pluricaulis Choisy (Convulvulaceae), Clitoria ternatea Linn. (Papilionaceae), and Evolvulus alsinoides Linn. (Convulvulaceae). Simple, accurate and precise RP-HPLC-PDA method was established for quality assessment and discrimination of Shankhpushpi samples using chromatographic profiling method. In distinction to the routine method of quality assessment which uses single or dual marker peaks, all chromatographic data (retention times/variables) were used. Fifteen shankhpushpi samples were purchased from the market including authenticated samples of all three C. pluricaulis, C. ternatea, E. alsinoides. A total of 18 samples were analyzed by HPLC and the dataset was then treated with multivariate analyses like PCA and HCA by using MINITAB software. Thus, the developed method was useful in discriminating the Shankhpushpi samples and for the perseverance of quality control.     

Gas chromatographic-mass spectroscopic determination of benzene in indoor air during the use of biomass fuels in cooking time

A gas chromatography-mass spectroscopic method in electron ionization (EI) mode with MS/MS ion preparation using helium at flow rate 1 ml min(-1) as carrier gas on DB-5 capillary column (30 m x 0.25 mm i.d. film thickness 0.25 microm) has been developed for the determination of benzene in indoor air. The detection limit for benzene was 0.002 microg ml(-1) with S/N: 4 (S: 66, N: 14). The benzene concentration for cooks during cooking time in indoor kitchen using dung fuel was 114.1 microg m(-3) while it was 6.6 microg m(-3) for open type kitchen. The benzene concentration was significantly higher (p < 0.01) in indoor kitchen with respect to open type kitchen using dung fuels. The wood fuel produces 36.5 microg m(-3) of benzene in indoor kitchen. The concentration of benzene in indoor kitchen using wood fuel was significantly (p < 0.01) lower in comparison to dung fuel. This method may be helpful for environmental analytical chemist dealing with GC-MS in confirmation and quantification of benzene in environmental samples with health risk exposure assessment.     

Remarkable solvent effect in Barton-Zard pyrrole synthesis: application in an efficient one-step synthesis of pyrrole derivatives

A unique solvent effect encountered in the Barton-Zard pyrrole synthesis was exploited to develop an efficient synthesis of pyrrole-2-esters. The chemistry was extended to a one-pot synthesis of pyrrole-2,4-dicarboxylates.     

Natural polyene α-pyrones. Total synthesis of citreomontanin from penicillium pedomontanum.

A total synthesis of all-$\text{E}$-citreomontanin (7), a novel polyene α-pyrone produced by $\text{Penicillium pedomontanum}$, is described.     

Growth morphology of isotactic polybutene-1

Isotactic polybutene-1 has been crystallized from solution by the film formation method. Well-defined single crystals have been grown from solutions of the polymer in amyl acetate and its mixtures with n-butanol in all the three modifications by varying the concentration and crystallization temperature. Multilayered orthorhombic, tetragonal and hexagonal crystals with spiral ramps and terraces have been obtained from concentrated solutions near the turbidity temperature. Rotation of the screw dislocation as well as interlacing multilayered growth have been observed in the tetragonal morphology. Different types of twinning are commonly observed in the orthorhombic and hexagonal modifications. It is suggested that (a) spiral ramps grow by the mechanism of screw dislocation, (b) terraced crystals grow by the mechanism of Frank-Read source or the basal lamellae being hairy on the molecular level nucleating the next lamella, (c) movement of screw dislocation is very common in the orthorhombic and hexagonal modifications, (d) the solution temperature does not affect the morphology but the solvent concentration and the crystallization temperature decide the growth habit of the single crystals and (e) the growth mechanism of multilayered crystals and twinning are similar to those of monomeric substances.