Publications by authors named "Mohmad Shafi Sheikh"

The interaction between cationic symmetrical gemini alkanediyl-α,ω-bis(dimethylcetylammonium bromide) series (16-s-16, s = 5, 6, abbreviated as G5 and G6) with hydrotropes (cationic: aniline hydrochloride, para-toluidine hydrochloride, and ortho-toluidine hydrochloride; nonionic: phenol, resorcinol, and pyrogallol) in aqueous medium has been investigated at four different temperatures ranging from 298.15 to 313.15 K.

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The purpose of this study was to determine the aggregation behavior of amphiphilic drug amitriptyline hydrochloride (AMT) and to search for means which boost/suppress the aggregation behavior. Polyethylene glycols (PEGs) nonionic polymers (which are used as pharmaceutical excipients) of varying molecular weights from 400 to 35,000 were tested. To know their effect on the micellization and interfacial behavior of the drug, the critical micelle concentration (CMC) and critical aggregation concentration (CAC) were determined in presence of various polymers by tensiometric and conductivity methods.

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Micellization of binary systems of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide) (16-4-16) and cationic/nonionic hydrotropes (aniline-hydrochloride, 2-methylanilinehydrochloride, 4-methylanilinehydrochloride, hydroxybenzene, 1,3-benzenediol, benzene-1,2,3-triol) have been studied using a conductometric technique. The critical micelle concentrations (cmc) for different mixing mole fractions at different temperatures have been calculated. To explain and compare the results, theoretical models of Clint, Rubingh and Motomura have been used to obtain the ideal cmc, mixed micelle composition, interaction parameters (β(m)), free energies of micellization, and activity coefficients.

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The interaction between cationic gemini hexanediyl-1,6-bis(dimethylcetylammonium bromide) (16-6-16, abbreviated as G6) with conventional cationic cetylpyridinium chloride (CPC), anionic sodium bis(2-ethyl hexyl)sulfosuccinate (AOT) and nonionic polyoxyethylene 10 cetyl ether (Brij56) in aqueous medium has been investigated at 25 degrees C. Different physicochemical properties such as critical micelle concentration (cmc), surface excess concentration (Gamma(max)), minimum area per molecule (A(min)), and interaction parameters (beta(m), beta(sigma)) as well as other thermodynamic and micellar properties have been determined. The interfacial and bulk behaviors were explored using theoretical models of Clint, Rubingh, Rosen, Motomura, and Maeda for justification and comparison of results of different binary combinations with the geminis of alkanediyl-alpha,omega-bis(dimethylcetylammonium bromide) series.

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The interfacial and micellization properties of binary and ternary mixtures of Gemini homologues, viz., tetramethylene-1,4-bis(N-hexadecyl-N,N-dimethylammonium bromide), pentamethylene-1,5-bis(N-hexadecyl-N,N-dimethylammonium bromide), and hexamethylene-1,6-bis(N-hexadecyl-N,N-dimethylammonium bromide), with various compositions were investigated at 25 degrees C using conductometric and tensiometric measurements. The micellar and adsorption characteristics like composition, activity coefficients, mutual interaction parameter, minimum area per molecule, free energy of micellization and adsorption have been evaluated and compared.

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Mixed micellization and surface properties of binary mixtures of cationic gemini surfactant butanediyl-alpha,omega-bis(dimethylcetylammonium bromide) (G4, 16-4-16) with conventional surfactants cetylpyridinium chloride (CPC), sodium bis(2-ethylhexyl)sulfosuccinate (AOT), and polyoxyethylene 10 cetyl ether (Brij56) have been studied using conductometric and tensiometric methods. To explain and compare the results theoretical models of Rubingh, Rosen, Clint, and Maeda have been used to obtain the interaction parameter, minimum area per molecule, surface excess, mixed micelle composition, free energies of micellization and adsorption, and activity coefficients. The activity coefficients and experimental critical micelle concentration (cmc) values are less than unity indicating synergism in micelles as well as at interface.

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