Surfactant-polysaccharide complexes based on quaternized chitosan. Characterization and application to emulsion stability

International audienceThe interactions between a polyelectrolyte and an oppositely charged surfactant allows obtaining complexes with specific properties. Such complexes between a quaternized chitosan, obtained from the reaction between chitosan and quaternary ammonium epoxides, and sodium 1-decanesulfonate were studied. Physico-chemical characteristics were obtained from conductimetric experiments as well as surface tension studies. A strong associative electrostatic interaction between the polysaccharide and the surfactant was shown from conductimetric experiments and a degree of association equal to 0.74 was determined. The complex presents better interfacial properties than surfactant and polysaccharide alone. The critical aggregation concentration is much smaller than the critical micellar concentration of the surfactant alone in solution. Moreover the viscoelastic moduli of the interfacial layer was increased in presence of the complex by comparing with surfactant alone. All these considerations allow using the surfactant-polysaccharide complex as a better emulsion stabilizer than either surfactant or polysaccharide alone

WHY DO VENTURE CAPITAL COMPANIES SYNDICATE?

Financial theory, access to deal flow, selection and monitoring skills are used to explain syndication in venture capital (VC) firms in six European countries. In contrast with US findings, portfolio management motives are more important for syndication than individual deal management motives. Risk sharing, portfolio diversification and access to larger deals are more important than selection and monitoring of deals. This holds for later stage and for early stage investors. Value adding is a stronger motive for syndication for early stage investors than for later stage investors, however. Non-lead investors join syndicates for the selection and value adding skills of the syndicate partners.

Rheological Evaluation of Silicon/Carbopol Hydrophilic Gel Systems as a Vehicle for Delivery of Water Insoluble Drugs

The present study analyzed the thickening properties of Carbopol 974 and 971 in a 50:50 mixture of water/Silsense™ A-21, a new cationic silicon miscible in any proportion with water. Samples were prepared by simply dispersing different Carbopol amounts (0.5–4%) at room temperature or at 70°C without neutralizing. Temperature sweep and time sweep analysis did not reveal significant structural changes at increasing temperature in the samples prepared following the first procedure. On the other hand systems obtained at 70°C possessed higher elastic character particularly at polymer concentration higher than 2% (w/v). Analysis of the G′ and G″ vs frequency curves by using different fitting equations (linear fitting, power law) gave information about the viscoelastic properties of the systems. The fitting of the frequency spectra and the calculation of the relaxation times from the master curves outlined the structural differences within the samples prepared with the two different procedures, confirming stronger gel-like behaviour for the samples prepared by the heating procedure. High preparation temperature promoted the polymer–solvent interactions, aiding the solvation of Carbopol. Heating facilitated polymer–solvent and polymer–polymer interaction, giving rise to a better organised structure typical of gel-like systems. Furthermore this preparation method provided good stability properties as shown by the stress sweeps tests performed during the three months of storage. The interpretation of the rheological results was supported by statistical analysis. A design methodology (screening and optimisation) was also applied in order evaluate the influence on dynamic rheological moduli of several parameters (polymer type and concentration, preparation method, temperature of the tests). This last method showed the relevance of the interaction of two main factors: polymer concentration and preparation procedure. Thus, statistical analysis confirmed that temperature increased the polymer–solvent interaction and improved the viscoelastic properties of the systems, particularly when Carbopols were present in considerable amounts

Private equity and entrepreneurial management in management buy-outs

Critics claim that short-term profit orientation and high deal price strategies of private equity (PE) firms can negatively affect the ability of management buyouts to initiate and sustain entrepreneurial management. This study investigates this claim by comparing effects of majority PE backed and other buy-outs at different levels of financial leverage on post buy-out increases in entrepreneurial management. We propose that PE can be used as an organizational refocusing device that simultaneously increases entrepreneurial and administrative management. We find that majority PE-backed buy-outs significantly increase entrepreneurial management practices. Furthermore, the increased financial leverage positively affects administrative management in management buy-outs. However, the effect of high financial leverage is larger for majority PE-backed buy-outs. These results support the notion that PE firms help buy-out companies develop ambidextrous organizational change: i.e. simultaneously develop entrepreneurial and administrative management practices. The findings have important implications for practitioners and policy makers