Structure and dynamics of nanoemulsions: Insights from combining dynamic and static neutron scattering

Despite their lack of thermodynamical stability, nanoemulsions can show a remarkable degree of kinetic stability. Among the various different preparation methods the phase-inversion concentration method is particularly interesting as it occurs spontaneously. Here we investigate such a system composed of a surfactant, cosurfactant, and oil that upon dilution with water forms long time metastable oil-in-water nanoemulsion droplets. The dynamics of the amphiphilic monolayers and its elastic properties is important for their stability and therefore the monolayer dynamics have been investigated by neutron spin echo (NSE). Despite the difficulties arising from the inherently polydisperse nature and the large number of different components necessarily contained in commercial nanoemulsion formulations, information concerning the membrane rigidity was extracted from the combination of small angle neutron scattering and NSE and several different formulations are compared. These results show that small amounts of different admixed ionic surfactants can modify the monolayer rigidity substantially and similarly effects of surface bound polyelectrolytes have been evaluated

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible additionfragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aq ueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate

Universal polymer analysis by 1H NMR using complementary trimethylsilyl end groups

New degenerative chain transfer agents, namely 4-(trimethylsilyl)benzyl 4-(trimethylsilyl)butane-dithioate, 4-(trimethylsilyl)benzyl 3-(trimethylsilyl)propyl trithiocarbonate and their 3-(trimethylsilyl)benzyl isomers, that are two-fold labeled with complementary trimethylsilyl (TMS) markers, were designed and shown to be powerful tools for universal polymer analysis by conventional 1H NMR spectroscopy. Their use in controlled free radical polymerization, here the reversible addition-fragmentation chain transfer (RAFT) method, resulted in polymers with low polydispersities up to high molar masses, as well as with defined complementary TMS end groups. Thus, routine 1H NMR spectra allowed facile determination of the molar masses of polymers of various chemical structures up to at least 105 g/mol, and simultaneously provided crucial information about the content of end groups that is typically >95% when polymerizations are correctly performed. Polymerizations were carried out in various solvents for two standard monomers, namely n-butyl acrylate and styrene, as well as for two specialty monomers, so-called inimers, namely 2-(2-chloropropionyloxy)ethyl acrylate and 2-(2-chloropropionyloxy)ethyl acrylamide. The complementary end group markers revealed marked differences in the suitability of commonly used solvents for RAFT polymerization. The results demonstrate—beyond good polymerization control—that the new RAFT agents are universal, powerful tools for facile polymer analysis by routine 1H NMR spectroscopy, of their absolute molar masses as well as of the content of end groups. This is crucial information, e.g., for the synthesis of high-quality telechelics and, in particular, of block copolymers, which is difficult to obtain by other methods. Preliminary screening experiments indicate that similar uses can be envisaged for analogous ATRP systems

Well-defined synthetic polymers with a protein-like gelation behavior in water

Homopolymers of N-acryloyl glycinamide were prepared by reversible addition-fragmentation chain transfer polymerization in water. The formed macromolecules exhibit strong polymer?polymer interactions in aqueous milieu and therefore form thermoreversible physical hydrogels in pure water, physiological buffer or cell medium

Waschkraft verbessernde polymere Wirkstoffe auf Basis von Polyvenylamiden

The aim of the invention is to improve the primary washing efficiency of washing and cleaning agents, in particular with respect to oil- and/or fat-containing dirt. Said aim is substantially achieved by incorporating polymers having an aggregation parameter Xag, where Xag >1 m N/