The surface activity of non-ionic copolymers (original) (raw)
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Langmuir, 2000
Surface tension measurements have been made on aqueous solutions of anionic monoesters of an alternating copolymer of maleic acid and styrene, MAS-n ,with n) 0-10, in the presence of alkyltrimethylammonium surfactants. It was found that the surface activity of these mixtures is increased relative to that observed for the pure components. This synergistic effect was ascribed to the formation of a complex, and its dependence of the complex structure was studied. The standard free energy of adsorption per methylene group was found to be-1.4 kJ mol-1 for complexes formed with MAS. This value decreases for MAS-n, becoming equal to zero for longer linear alkyl chains. However, all the calculated values of the standard free energy were negative and lower than those obtained for the pure surfactant. These results indicate that the main contribution to this change of free energy is the neutralization of the negative charge by a hydrophobic cation.
Surface Chemistry of Surfactants and Polymers
2014
Surfactant is a widely used contraction for surface active agent, which literally means active at a surface. The term surface active means that the surfactant reduces the free energy of surfaces and interfaces. Expressed differently, they reduce the surface and the interfacial tensions. This is not an unique quality, however. Most water-soluble organic compounds give a reduction of the surface and interfacial tensions when added to an aqueous solution but the effect is normally much less pronounced than for surfactants. The unique behavior of a surfactant is that it self-assembles at interfaces and forms tightly packed structures: monolayers at the air-water and the oil-water interface, and monolayers and aggregates at the solid-water interface. Such self-assembled layers drastically change the character of the interface. Surfactant self-assembly at the air-water interface, commonly referred to as the "surface," is dealt with in Chapter 12; the assembling at the oil-water interface, which is key to formation of emulsions, is treated in Chapter 24; and assembly at the solid-water interface, adsorption, is described in depth in Chapter 8. Surfactants also self-assemble in water, usually forming micelles at very low concentration and other aggregates, called surfactant liquid crystals, at higher concentration. These are treated in Chapters 4 and 6, respectively. The term surfactant is usually associated with relatively low molecular weight substances. The molecular weight is typically below 500 Da but may be larger for nonionic surfactants with long polyoxyethylene tails. There also exist polymeric surface active agents and these may be called polymeric surfactants. However, more often they are referred to as surface active polymers and that terminology is used in this book. Several chapters deal with surface active polymers.
Polymer-surfactant Interactions
Journal of Thermal Analysis and Calorimetry, 2001
The phase behavior and some physicochemical properties of homopolymers (HP) and hydrophobically modified (HMP) polymers, as well as of polyelectrolytes (PE) and proteins (PR), in the presence of aqueous surfactants, or their mixtures, are discussed. Mixing the above components gives rise to the formation of organized phases, whose properties are controlled by polymer and/or surfactant content, temperature, pH, and ionic strength. Depending on the nature, concentration, and net charge of both solutes, molecular solutions, polymer-surfactant complexes, adsorption onto micelles and vesicles, gels, liquid crystalline phases, and precipitates are observed. Such rich polymorphic behavior is the result of a complex balance between electrostatic, excluded volume, van der Waals, and other contributions to overall system stability. It is also modulated by the molecular details and architecture of both the polymer and the surfactant. Different experimental methods allow investigation of the above systems and getting information on the nature of polymer-surfactant interactions (PSI). Surface adsorption and thermodynamic methods, together with investigation of the phase diagrams, give information on the forces controlling PSI and on the existence of different phases. Conductivity, QELS and viscosity allow estimating the size and shape of polymer-surfactant (protein-surfactant) complexes. Optical microscopy, cryo-TEM, AFM, NMR, fluorescence, and relaxation methods give more information on the above systems. Use of the above mixtures in controlling gelation, surface covering, preparing dielectric layers, and drug release is suggested.
Langmuir, 2011
Complex formation between oppositely charged polyelectrolytes and surfactants has been an important subject of research for both fundamental and application reasons. 1À7 PolymerÀ surfactant mixtures are widely exploited in commonplace formulations to manipulate their performance behaviors. The ternary systems of surfactant, polymer, and water have potential for domestic, industrial, and technological applications, viz., foods, paints, drug delivery, coatings, laundry products, cosmetics, etc. 8,9 In such applications, polymers are mainly used as viscosity modifiers and stabilizers. Oppositely charged polymerÀ micellar aggregates can serve as models for polyionÀcolloid systems. 10 The Coulombic polyionÀcolloid interaction guides the flocculation of inorganic materials important in water purification. 11,12 Although the field is continuously being explored, information on combinations of different kinds is yet not adequate from the standpoint of fundamental understanding and applications.
Interactions of an anionic surfactant with poly(oxyalkylene) copolymers in aqueous solution
Journal of Colloid and Interface Science, 2009
The interactions of sodium dodecyl sulfate (SDS) with poly(ethylene oxide)/poly(alkylene oxide) (E/A) block copolymers are explored in this study. With respect to the specific compositional characteristics of the copolymer, introduction of SDS can induce fundamentally different effects to the self-assembly behavior of E/A copolymer solutions. In the case of the E 18 B 10-SDS system (E = poly(ethylene oxide) and B = poly(butylene oxide)) development of large surfactant-polymer aggregates was observed. In the case of B 20 E 610-SDS, B 12 E 227 B 12-SDS, E 40 B 10 E 40-SDS, E 19 P 43 E 19-SDS (P = poly(propylene oxide)), the formation of smaller particles compared to pure polymeric micelles points to micellar suppression induced by the ionic surfactant. This effect can be ascribed to a physical binding between the hydrophobic block of unassociated macromolecules and the non-polar tail of the surfactant. Analysis of critical micelle concentrations (cmc *) of polymer-surfactant aqueous solutions within the framework of regular solution theory for binary surfactants revealed negative deviations from ideal behavior for E 40 B 10 E 40-SDS and E 19 P 43 E 19-SDS, but positive deviations for E 18 B 10-SDS. Ultrasonic studies performed for the E 19 P 43 E 19-SDS system enabled the identification of three distinct regions, corresponding to three main steps of the complexation; SDS absorption to the hydrophobic backbone of polymer, development of polymersurfactant complexes and gradual breakdown of the mixed aggregates.
Surface activity of hydrophobically modified alternating copolymers
Polymer, 2004
Surface activity of N-monopropyl maleamic acid-alt-styrene (NPMA-alt-S) and N-monodecyl maleamic acid-alt-styrene (NDMA-alt-S) was studied. Surface pressure -area isotherms ðP -AÞ at the air/water interface were determined. It was found that the pH of the water subphase and the chemical structure of the copolymers studied strongly influence the type of isotherms. It was also found that the driving force for the adsorption of NPMA-alt-S, water soluble polymer at the air/water interface arises from an entropic contribution. q
Effect of Head Groups, Temperature, and Polymer Concentration on Surfactant—Polymer Interactions
Journal of Surfactants and Detergents, 2014
The micellization behaviour of sodium dodecyl sulphate, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetylpyridinium chloride in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations (0.005-0.04 %, w/v) has been studied at different temperatures (288.15-318.15 K) using conductivity, surface tension, and viscosity methods. From conductivity measurements various micellar parameters, like critical micellar concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (b), and standard free energy of transfer (DG 0 t), have been calculated. CAC values have been found to decrease with polymer concentration and increase with temperature. However, the PSP values increase with both polymer concentration and temperature for all surfactants. Similar parameters have also been calculated from surface tension data (CMC r , CAC r , PSP r) along with other parameters such as maximum surface excess concentration at the air/water interface (C max), minimum area per molecule (A min), and packing parameter (p). The CMC r , CAC r , and PSP r values are smaller than the corresponding CMC, CAC, and PSP values, but both show similar behaviour with temperature and concentration of polymer. Various parameters indicate that the presence of the aromatic ring in the head group of surfactant decreases its interaction with PEO, whereas the increased hydrophobicity in the tail leads to stronger interactions with PEO. Viscosity studies further supplement the conclusions drawn from the above results.