Self-assembly in solution and adsorption at the air-water interface and at solid surfaces were investigated for two amino-acid-based surfactants with conductimetry, NMR, tensiometry, quartz crystal microbalance with monitoring of the dissipation (QCM-D), and surface plasmon resonance (SPR). The surfactants studied were sodium N-lauroylglycinate and sodium N-lauroylsarcosinate, differing only in a methyl group on the amide nitrogen for the sarcosinate. Thus, the glycinate but not the sarcosinate surfactant is capable of forming intermolecular hydrogen bonds via the amide group. It was found that the amide bond, N-methylated or not, gave a substantial contribution to the hydrophilicity of the amphiphile. The ability to form intermolecular hydrogen bonds led to tighter packing at the air-water interface and at a hydrophobic surface. It also increased the tendency for precipitation as an acid-soap pair on addition of acid. Adsorption of the surfactants at a gold surface was also investigated and gave unexpected results. The sarcosine-based surfactant seemed to give bilayer adsorption, while the glycine derivative adsorbed as a monolayer.

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We have studied nucleation and crystal growth of calcium carbonate on hard surfaces, i.e. stainless steel and silica, at different temperatures, in relation to the corresponding bulk processes, using scanning electron microscopy (SEM), X-ray diffraction (XRD), and ellipsometry. In the bulk solution, a mixture of all three calcium carbonate crystalline polymorphs, calcite, aragonite, and vaterite, as well as amorphous particles was observed at 25 °C, while at 55 °C aragonite and calcite crystals dominated. On surfaces only calcite crystals were observed at 25 °C, whereas aragonite and calcite crystal adsorbed on the surfaces at 55 °C. Two kinds of nucleation and adsorption mechanism of CaCO3 crystals on hard surfaces were observed, depending on the surface orientation (vertical or horizontal, i.e., subject to sedimentation) in the bulk solution. A model for the relation between interfacial layer structure, the substrate, and the solution crystallization is discussed based on the observed difference in deposition between type of surfaces and surface orientation. In addition, the effect of magnesium ion on the morphology of calcium carbonate crystals is discussed.

The adsorption of three dicarboxylic amino acid-based surfactants, disodium N-lauroylaminomalonate, disodium N-lauroylaspartate, and disodium N-lauroylglutamate, has been studied by surface plasmon resonance (SPR) and the quartz crystal microbalance with dissipation monitoring (QCM-D). These surfactants have high cmc values, which means that the unimer concentration is high at the plateau value of adsorption. This gives rise to a considerable "bulk effect", which must be deducted from the observed value in order to obtain the true value of the adsorbed amount. In this article, we show how this can be done for the QCM-D technique. Adsorption is studied on silica, gold, gold hydrophobized by a self-assembled layer of an alkane thiol, and hydroxyapatite. Adsorption on hydroxyapatite differs very much among the three surfactants, with the aspartate derivative giving the strongest and the glutamate giving the weakest adsorption. This difference is explained as the difference in ability of the dicarboxylic amphiphiles to chelate calcium in the crystal lattice.

The adsorption of and conformation adopted by a branched-linear polymer conjugate to the hydrophilic silica-aqueous solution interface have been studied by in situ null ellipsometry and Monte Carlo simulations. The conjugate is a highly branched polyethyleneimine structure with ethyleneoxide chains grafted to its primary and secondary amino groups. In situ null ellipsometry demonstrated that the polymer conjugate adsorbs to the silica surface from water and aqueous solution of 1 mM asymmetric divalent salt (calcium and magnesium chloride to emulate hard water) over a large pH range. The adsorbed amount is hardly affected by pH and large charge reversal on the negatively charged silica surface occurred at pH = 4.0, due to the adsorption of the cationic polyelectrolyte. The Monte Carlo simulations using an appropriate coarse-grained model of the polymer in solution predicted a core-shell structure with no sharp boundary between the ethyleneimine and ethyleneoxide moieties. The structure at the interface is similar to that in solution when the polymer degree of protonation is low or moderate while at high degree of protonation the strong electrostatic attraction between the ethyleneimine core and oppositely charged silica surface distorts the ethyleneoxide shell so that an "anemone"-like configuration is adopted. The adsorption of alkyl benzene sulfonic acid (LAS) to a preadsorbed polymer layer was also investigated by null ellipsometry. The adsorption data brought additional support for the existence of a strong polymer adsorption and showed the presence of a binding which was further enhanced by the decreased solvency of the surfactant in the salt solution and confirmed the surface charge reversal by the polymer adsorption at pH = 4.0.

We form and investigate foams stabilized by a triple surfactant mixture containing a nonionic alkyl polyglucoside (APG) in addition to the combination of ionic sodium lauryldioxyethylene sulphate (SLES) and zwitterionic cocamidopropyl betaine (CAPB) surfactants. APG improves the surfactants compatibility at alkaline pH. The addition of a readily biodegradable chelating agent methylglycinediacetic acid (MGDA) in the mixture contributes further for the excellent performance even in very hard water. Foam properties are analyzed and compared to those of the single components and to the binary mixture without APG. Foam drainage is successfully controlled by introducing additives suitable for the alkaline conditions: fatty alcohol and/or hydrophobically modified starch. Systematic model experiments are performed to characterize the surface tension and dilatational rheology, and thin films drainage. Slowed foam and thin films drainage is confirmed to correlate with the increased surface visco-elasticity in the presence of fatty alcohols. Temperature impact on the surface properties is used for fine tuning of the foam drainage.

Ergebnisse aus semiempirischen (MND0)-Berechnungen der Bindungslangen, Bildungsenergien und UberschuDladungen solcher Verbindungsklassen 6, 7 und 8, die als gemeinsames Strukturelement einen N-Alkylpyridinium-Molekiilteil besitzen (vgl. Tab. l), lassen allgemeingiiltige Trends erkennen, mit deren Hilfe wichtige Reaktivitatsmerkmale dieser Reihe vorhergesagt werden kiinnen und somit AnlaD zur gezielten Herstellung der Beispiele 9, 24 und 26 und deren erste Verwendungstests waren: Insbesondere die C1-N2-Bindungslange kann bei Umsetzungen mit nucleophilen Reaktionspartnern -bei zusatzlicher Beriicksichtigung der entsprechend GI. (3) (9)] als hinreichend fur die durch den anomeren Effekt gesteuerte nucleophile Substitution des Pyridiniumteils in 24a klassifiziert werden. Wihrend also ,,normale" N-Alkylpyridiniumsalze (z. B. das N-Methylpyridinium-Kation 6b) kaum an der C1-Position angreifbar sind, kann durch gezielte Ausnutzung des anomeren Effekts das praparative Anwendungsspektrum dieses Strukturelements nunmehr deutlich erweitert werden (hier umrissen durch die Herstellung der Verbindungen 5, 9h, 17 und 22 aus 9.2% und 25b aus .24a sowie 27a aus %a).Unlangst konnten wir zeigen, daD dem Gleichgewicht (1) eine maogebliche Bedeutung bei der produktadaptierten Lenkung der gleichzeitigen Umsetzung von .4cylchloriden The results of semiempirical MNDO calculations on bond lengths, heats of formation, and net atomic charges of compounds 6, 7, and 8, which all contain an N-alkylpyridinium moiety (see Table I), allow general trends to be recognized. These trends allow the prediction of important reactivity characteristics of this series of compounds and were the reason for the synthesis of compounds 9, 24, and 26 and for tests of their usefulness. Specifically, the C1 -N2 bond length serves as a useful criterion for the reactivity with nucleophilic partners, especially in combination with thermodynamic data calculated from reactions (3) and (4) ( Tables 3 and 4). In 7 and 8, this bond is very long as a consequence of an extreme anomeric effect. This observation is reflected in the (experimentally tested) property of the complexes 9 to split off the pyridine moiety. The CI atom in 6a does not influence the Cl-N2 bond length but it does activate the C1 atom toward nucleophilic attack and can itself function as the leaving group [see eq. (lo)]. -A remarkable example, both on the basis of the MNDO results (using the model compound 6i) and from the experimental viewpoint, was observed for the class of compounds Ma: The calculated CI -N2 bond length of 6i (1.563 A) could be classified as adequate for nucleophilic substitution of the pyridine moiety controlled by the anomeric effect on the basis of experimental tests. Whereas "normal" N-alkylpyridinium salts (e.g. the N-methylpyridinium cation, 6b) are hardly ever attacked in the C1 position, the preparative usefulness of this structural element can now be considerably increased by use ofthe anomeric effect. This is demonstrated by the synthesis of compounds 5,9h, 17, and 22 from ...

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