The effect of polymers on the phase behavior of balanced microemulsions: diblock-copolymer and comb-polymers (original) (raw)
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Applied Physics A: Materials Science & Processing, 2002
The effect of amphiphilic block copolymers on ternary microemulsions (water, oil and non-ionic surfactant) is investigated. Small amounts of PEP-PEO block copolymer lead to a dramatic expansion of the one-phase region where water and oil can be solubilized by the mediation of surfactant molecules. Small-angle neutron-scattering experiments employing a high-precision two-dimensional contrast-variation technique demonstrate that the polymer is distributed uniformly on the surfactant membrane, where it modifies the membrane curvature elasticity. Furthermore, a new approach to determine the bending rigidity of an amphiphilic membrane is proposed, which is precise enough to measure the logarithmic scale dependence of the bending rigidity and its universal prefactor in bicontinuous microemulsions. PACS: 61.12.Ex; 68.05.Gh; 61.25.Hq Membrane systems represented by surfactant monolayers in microemulsions or by lipid bilayers have received much interest recently. Experimentally the interaction between polymers and membranes, which is very common in all kinds of biological membranes, has been studied intensively. A good example is "stealth liposomes" effective drug carrier systems where polymers anchored to phospholipid bilayers protect artificial vesicles against the body's immune response . Theoretically the concept of the curvature elasticity [2] has been found to be very useful in understanding many phenomena in these systems, which are the shapes, fluctuations, phase behavior and more. For a detailed comparison of theory and experiment, it is necessary to measure the parameters of this model, which are the spontaneous curvature c 0 , the bending rigidity κ, and the saddle-splay modulusκ.
Journal of Colloid and Interface Science, 2006
Dynamic light scattering (DLS) and fluorescence recovery after pattern photobleaching (FRAPP) were used to study the interaction of low molecular weight poly(ethylene glycol) (PEG) with micelles of two different surfactants: tetradecyldimethyl aminoxide (C 14 DMAO, zwitterionic) and pentaethylene glycol n-dodecyl monoether (C 12 E 5 , non-ionic). By using an amphiphilic fluorescent probe or a fluorescent-labeled PEG molecule, FRAPP experiments allowed to follow the diffusion of the surfactant-polymer complex either by looking at the micelle diffusion or at the polymer diffusion. Experiments performed with both fluorescent probes gave the same diffusion coefficient showing that the micelles and the polymer form a complex in dilute solutions. Similar experiments showed that PEG interacts as well with pentaethylene glycol n-dodecyl monoether (C 12 E 5).
Journal of Surfactants and Detergents, 2017
The interactions of two gemini surfactants (16s-16, s = 5, 6) and their conventional counterpart cetyltrimethylammonium bromide (CTAB) with polyethylene glycols (PEG 3000 and PEG 35000) have been investigated using conductivity, steady state fluorescence, viscosity and TEM techniques. The results indicate that there is no interaction between the PEG 3000/CTAB complex at lower polymer concentrations. However, a very weak interaction is observed at higher concentrations (0.5 and 1.0 wt% PEG 3000), while PEG 3000 and PEG 35000 interact with the gemini surfactants. Both critical aggregation concentration (CAC) and critical micelle concentration (CMC) increases with polymer concentration but are independent of the polymer molecular weight. From steady state fluorescence it is found that the addition of PEG results in no drastic decrease in the aggregation number (N) for all surfactants. This suggests that the atmosphere surrounding the polyion-bound micelles, with respect to the influence on the forces acting at the micelle surface, is equivalent to the counterion/water atmosphere surrounding free micelles. The relative viscosity (g r) results show an enhancement in g r for all the surfactants. The increase in g r is quite significant with gemini surfactants. Polymer-surfactant interaction also depends on the polymer molecular weight. Also, the interaction seems to affect both inter polymer-polymer association as well as chain expansion. Additionally the surfactant induced changes in the polymer conformation depicted by TEM study at the micro structural level confirmed previously observed interactions determined by different analytical techniques.
Colloid and Polymer Science, 2006
Phase behaviors of AOT/ heptane (Hp)/formamide (FA), ethylene glycol (EG), propylene glycol (PG), triethylene glycol (TEG) and glycerol (GLY) have been investigated in the absence and presence of a nonionic surfactant, polyoxyethylene (2) cetyl ether (Brij-52) at 303 K. The phase characteristics of (AOT+ Brij-52)/Hp/(EG or PG or TEG) have been found to be different from that of AOT/Hp/FA systems in respect of both the area of monophasic domain and the appearance of other mesophases. The area of monophasic domain of (AOT+Brij-52)/Hp/EG depends on the content of Brij-52 (X Brij-52) and shows a maximum at X Brij-52 =0.4. A negligible effect on the area of the monophasic domain has been shown by more hydrophobic surfactants, polyoxyethylene(2) stearyl ether (Brij-72) and polyoxyethylene(2) oleyl ether (Brij-92). The effect of oils (dodecane and hexadecane) on the mixed systems stabilized by (AOT+Brij-52) in EG has been investigated. The area of monophasic domain has been found to be dependent on the type of nonaqueous solvents and follows the order GLY>EG>PG>TG. A systematic investigation on the measurement of phase volumes of mixed surfactant systems [AOT+nonionic surfactant(s)] stabilized in oils of different chain lengths (heptane, dodecane and hexadecane) and polar solvent (EG) has been carried out at different compositions of the ingredients to identify the phase transitions of these systems as a function of X Brij-52. The threshold point of phase transition (both W I→W IV and W IV→W II transitions) has been found to be a function of the configuration of added nonionic surfactant, nature of the polar solvent and oil. The conversion of the initial oil/EG droplets into EG/oil droplets with increasing X nonionic has been facilitated for hydrophobic surfactants polyoxyethylene (4) lauryl ether (Brij-30), Brij-52, and Brij-72 in comparison to the hydrophilic surfactants polyoxyethylene(10) cetyl ether (Brij-56) and polyoxyethylene(20) cetyl ether (Brij-58).
Advances in Colloid and Interface Science, 1992
Many polymer/surfactant formulations involve a trapped kinetic state that provides some beneficial character to the formulation. However, the vast majority of studies on formulations focus on equilibrium states. Here, nanoscale structures present at dynamic interfaces in the form of air-in-water foams are explored, stabilised by mixtures of commonly used non-ionic, surface active block copolymers (Pluronic ®) and small molecule ionic surfactants (sodium dodecylsulfate, SDS, and dodecyltrimethylammonium bromide, C 12 TAB). Transient foams formed from binary mixtures of these surfactants shows considerable changes in stability which correlate with the strength of the solution interaction which delineate the interfacial structures. Weak solution interactions reflective of distinct coexisting micellar structures in solution lead to segregated layers at the foam interface, whereas strong solution interactions lead to mixed structures both in bulk solution, forming interdigitated layers at the interface.
A SANS study of microemulsions with polymer additions
Mikroemulsionen bestehend aus Wasser, Öl, nicht-ionischem Tensid, und kleinen Mengen verschiedenen Polymers wurden mit zwei komplementären Methoden untersucht: Das makroskopische Phasenverhalten wurde bestimmt, und die dazugehörige mikroskopische Struktur wurde mit Neutronenkleinwinkelstreuung gemessen. Nachdem der "Polymer Boosting Effekt" etabliert wurde - dies ist eine große Verstärkung des Emulsifizierverhaltens durch amphiphiles Diblock Copolymer - ist der komplementäre Effekt von Homopolymeren Ziel dieser Studie. Simultane Beigaben von Homopolymeren und Diblock Copolymeren testen die Überlagerungsfähigkeit dieser beiden entgegengesetzten Effekte, um womöglich eine konstante Effizienz mit vergrößerter Viskosität zu erhalten. Desweiteren sollte der "Polymer Boosting Effekt" von der bikontinuierlichen zur Tröpfchen-Mikroemulsion übertragen werden. Dieser Teil der Arbeit zeigt einen Zusammenhang zwischen der Polymerstruktur und der Stärke des "Boosting Eff...