Synthesis and properties of di-n-dodecyl alpha,omega-alkyl bisphosphate surfactants Duivenvoorde, F.L.; Feiters, M.C.; Van der Gaast, S.J.; Engberts, J.B.F.N. IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document VersionPublisher's PDF, also known as Version of record Publication date : 1997 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Duivenvoorde, F. L., Feiters, M. C., Van der Gaast, S. J., & Engberts, J. B. F. N. (1997). Synthesis and properties of di-n-dodecyl alpha,omega-alkyl bisphosphate surfactants. Langmuir, 13(14), 3737-3743. https://doi.org/10.1021/la9620420 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Burg, Texel, The Netherlands Received November 25, 1996. In Final Form: April 7, 1997 Three gemini and two bolaform bisphosphate surfactants of the type 12-s-12, with s ) 6, 8, 12, 18, and 24 carbon atoms, have been synthesized and their aggregation behavior has been studied. The bolaform surfactants 12-18-12 and 12-24-12 were found to form vesicles in aqueous solution, as indicated by electron microscopy. The geminis 12-6-12, 12-8-12, and 12-12-12 form micellar structures. The cmc's of the geminis, obtained from conductivity measurements, spectroscopic methods, and microcalorimetry, are very low, on the order of 10 -4 to 10 -5 M. The cmc decreases with increasing spacer length. For the bolaform amphiphiles 12-18-12 and 12-24-12 noncooperative phase transitions are detected using fluorescence depolarization and DSC. NMR line-broadening studies display unusual behavior. The spacer within the 12-24-12 vesicles has been found to be membrane spanning, as confirmed by X-ray powder diffraction. IntroductionBolaform-type and gemini-type surfactants have gained much interest over the last years, because of their unusual aggregation properties, 1-10 compared to those of the corresponding conventional surfactants. Bolaform amphiphiles are found in natural membranes of archaebacteria, a class of organisms that live in habitats with extreme circumstances, such as high temperatures, low pH values, and saturated salt environments. 11 When there is a single spacer, this spacer is longer than the other chains and is therefore membrane spanning in such membranes. Other types of bolaform membranes consist of two membrane-spanning spacers. As a r...
The dispersing of pigments in powder coatings is a complicated process. Pigment agglomerates, which are present in an applied and fully cured powder coating, are due to insufficient dispersing. The exact reason for this poor dispersion is not yet clearly understood. Rheological properties of the powder coating resin are of major importance, since wetting of the pigments by the powder resin and deagglomeration of the pigment agglomerates during the dispersive mixing in an extruder are both influenced by the resin's viscosity. Recently, special attention is paid to this problem by industry, that has already led to the development of special pigment masterbatches and dispersing agents. In our research, the use of block copolymer dispersants is investigated, because block copolymer dispersants are expected to have advantages over low-molecular weight wetting agents. A novel block copolymer dispersant, with a poly(2-vinylpyridine) anchor block and a poly(E-caprolactone) buoy block, has been synthesized and tested in a polyester powder coating with Ti0 2 pigments. Based on qualitative electron microscopic determination, improvements in dispersion have not been observed so far, but the stability of a pigment dispersion was clearly improved by the addition of the block copolymer dispersant. The effect of the dispersants on the coating's appearance is currently under investigation. 262 IntroductionThe dispersing of pigments is one of the most difficult and crucial processes in the production of coatings, since the degree of dispersion influences many coating properties, such as gloss, hiding power, tinting strength, etc. The dispersion process in solvent-based and waterborne coatings is well studied
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