Volume 48, Issue 1

This paper presents the results from the research on the synthesis of new perfluorinated carbohydrate surfactants. Surface active properties were studied for new surfactants and their wettability was evaluated on selected solid surfaces.

Rhamnolipid is the simplest class of biosurfactants with a well defined structure. The main obstacle in commercialization of biosurfactant especially rhamnolipids is the higher cost of the production. The production cost can be reduced by using economical carbon sources. Glycerol residue is available from glycerin distillation plant at low cost. It can be used as carbon source for rhamnolipid production using Pseudomonas aeruginosa (ATCC 10145). The optimum concentration of glycerol residue was 5% weight by volume (w/v) yielding maximum rhamnolipids at 2.50 g/L in the broth. From batch monitoring of polyglycerol and monoglycerol consumption, it appeared that polyglycerols were first hydrolyzed to monoglycerol in the broth itself and consumed as carbon source. The product had components similar to rhamnolipids synthesized on pure glycerol under the same conditions. This indicated the potential of glycerol residue as economic substrate for production of rhamnolipids.

The study of binuclear complexes of copper(II) is a very active and highly interesting field due to their significance in bioinorganic chemistry, magneto chemistry, material science, superconductivity and multi electron redox chemistry. Due to the surface-active properties of copper(II) stearate with 2-aminobenzothiazole, the complexes exhibit many applications in agrochemical industries as dispersing agents, foaming and wetting agents. In the present investigation solid complexes of Cu(II) stearate with 2-amino-6-methoxybenzothiazole and 2-amino-6-nitrobenzothiazole have been synthesized and characterized by elemental analysis and their IR, NMR, ESR spectral studies. All the synthesized complexes are coloured and their purity was checked by Thin Layer Chromatography.

Due to their high enantioselectivity biotransformations, i.e. enzyme-catalysed conversion of organic compounds, are extremely attractive reactions. However, a limiting factor for choosing substrates is the enzyme-substrate incompatibility. This occurs when a hydrophilic enzyme which naturally resides in the aqueous cell cytoplasm is supposed to convert a hydrophobic substrate. In this context bicontinuous microemulsions appear to be a beneficial reaction medium for biotransformations, particularly due to their large interfacial area between a hydrophilic and a hydrophobic compound. As a “proof of concept” we performed ω-transaminase (EC 2.6.1.18) catalysed model reactions in a bicontinuous microemulsion of the type phosphate buffer/NaCl – n -octane – pentaethylene glycol monodecyl ether.

Structure of water/propylene glycol/ethoxylated mono-di-glyceride/peppermint oil/ethanol microemulsions solubilizing azithromycin has been investigated at room temperature by small-angle X-ray scattering (SAXS) technique. The scattering data were evaluated by Indirect Fourier Transformation (IFT) or Generalized Indirect Fourier Transformation (GIFT) methods depending on the aqueous phase content. The growth of the microemulsions droplets by increasing the water content and the effect of azithromycin incorporation in the microemulsions were investigated. The Indirect Fourier Transformation gives the real space pair-distance distribution function: a facile way for the quantitative estimation of structure parameters of the microemulsions. It was found that the size of the microemulsion aggregates or repeating distances in the microemulsion increases with the aqueous phase content. The maximum diameter of the drug free and drug loaded microemulsions aggregates depend on their microstructure. The values of the effective interaction radius of the microemulsions are higher for the drug free compared to the drug loaded microemulsions aggregates.

Here we study the influence of alkaline cations on the self-assembly of cetylpyridinium chloride and cetylpyridinium nitrate. It is known that the anionic counterions have a strong influence on the solubility and self-assembly properties of cationic surfactants. However, in this paper we will show that monovalent cations have also an influence which is weaker but detectable. Scattering techniques (X-Ray, light) were used to obtain structural information about the aggregation as a function of the temperature and the ionic strength. The results are interpreted in terms of ion pair adsorption at the micellar interface, depending on the ionic strength.

In Slovakia chlorhexidine is available in dosage forms of solutions, creams and pastes but not in the form of hydrogels, though they are modern drug forms with many positive properties. Therefore, in this article possibilities of its formulation into hydrogels are studied. In particular, two research aims were followed. The first consisted in study of an influence of surface active agents on the release of chlorhexidine dihydrochloride from chitosan hydrogels and the second one was to design a formulation of hydrogels for local delivery of chlorhexidine to the oral cavity. To this end, surfactants from the group of alkyltrimethylammonium bromides with the length of alkyl chain C 6 –C 18 which occupy a dominant position in the indication group of antiseptics and disinficients were analyzed with intention to use them in preparation of hydrogels. Hydrogels were prepared with 2.5% (w/w) gel-forming agent chitosan. Both the active agent and surfactants were used in 0.1% (w/w) concentration. It is shown that the surface active agents with short alkyl chain are suitable for development of chlorhexidine dihydrochloride hydrogels with controlled release.

The pH-stat technique was used to study the influence of various types of surfactants on the performance of polymers used as inhibitors for preventing the precipitation of calcium phosphate in industrial water systems. Four types of surfactants were evaluated: 1) anionic, 2) non-ionic, 3) amphoteric, and 4) cationic. The polymeric inhibitors studied include homo-, co-, and terpolymers containing different functional groups such as carboxylic acid, sulfonic acid, ester, and amide. It has been found that polymer dosage and polymer architecture play important roles in inhibiting calcium phosphate precipitation. The results on the evaluation of surfactants reveal that all surfactants are ineffective calcium phosphate inhibitors. Comparative inhibition data collected for various calcium phosphate inhibiting polymers in the presence surfactants containing different ionic charges are presented. Results are also discussed on the influence of cationic polymeric flocculant in preventing the precipitation of calcium phosphate by anionic polymeric inhibitors.

A novel nonpolluting type of calcium phosphate and iron(III) antiscalant MCn was synthesized. The observation shows that MCn causes a disordered calcium phosphate. Furthermore, both calcium phosphate and iron(III) inhibition increase with increasing degree of polymerization of MCn from 5 to 13, and the dosage of MCn plays an important role on calcium phosphate and iron(III) inhibition. Inhibition mechanism is proposed the interactions between calcium or iron ions and polyethylene glycol (PEG) are the fundamental impetus to restrain the formation of the scale in cooling water systems.

The pillared derivatives from δ-layered sodium disilicate were investigated by intercalation of bisoctyl dimethyl ammonium chloride and dioctadecyl dimethyl ammonium chloride. The influence of various parameters such as water content, pH of the mixture, and time were examined. The resultant samples were characterized by X-ray powder diffraction, Fourier transform infrared, and thermal gravimetric observation. The experimental results showed that δ-layered sodium disilicate was first transformed to kanemite (NaHSi 2 O 4 (OH) 2 · 2H 2 O), and subsequently kanemite was pillared with bisoctyl dimethyl ammonium chloride or dioctadecyl dimethyl ammonium chloride. The tribological properties of typical samples then were investigated by point contact test. The results show that the pillared derivatives have good load-carrying capacity and friction-reducing property.

The oxidation reactions of D-sucrose have been carried out with N-bromophthalimide in the presence of micellar aggregates at 45°C. The kinetics revealed first order dependence on N-bromophthalimide (NBP) and fractional order dependence on D-sucrose. Variation of mercuric acetate concentration has an insignificant effect on reaction rate. The stoichiometric ratio of NBP:D-sucrose was 1:2 and the oxidation product was aldonic acid confirmed by FeCl 3 –HCl test. The influence of salts on the reaction rate has also been studied. Phthalimide (NHP) and sulfuric acid (H 2 SO 4 ) inhibit the rate. Thermodynamic and activation parameters have been evaluated and a mechanism consistent with the kinetic data has been proposed. Cetyltrimethylammonium bromide (CTAB) and TritonX-100 (TX-100) catalyze the reaction, while sodium dodecyl sulfate (SDS) inhibits the rate of reaction. The applicability of Berezin's model was tested to explain the observed micellar effects. The rate constants (k M ) and binding constants (K S + K O ) have been evaluated.

A new kind of surfactants with chelating properties named N-acylethylenediamine triacetate (N-acyl ED3A) of different hydrocarbon chain lengths were synthesized from anhydrous ethylene diamine, fatty acid chlorides (Capryloyl, lauroyl, myristoyl, palmitoyl, stearoyl or oleoyl chloride) and chloroacetic acid. The chemical structures of the prepared compounds were confirmed using different spectroscopic techniques, primarily Fourier transform infrared spectroscopy and nuclear magnetic resonance. The surface properties including surface and interfacial tension, foaming height, emulsification power, calcium ion stability, stability to hydrolysis and critical micelle concentration (CMC) were determined. The trisodium N-acylethylenediamine triacetates have been found to combine the properties of strong surfactancy, extreme mildness with a high tolerance to water hardness, and ability to chelate metal ions, which indicates a promising application prospect in many fields.