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Characterization of Microemulsions by NMR
Published in Promod Kumar, K. L. Mittal, Handbook of Microemulsion Science and Technology, 2018
Bjorn Lindman, Ulf Olsson, Olle Soderman
Key ingredients in a physicochemical characterization of a microheterogeneous surfactant self-assembly system are (1) phase stability and phase behavior, (2) microstructure, and (3) local molecular arrangements, interactions, and dynamics. Microemulsions constitute but one type of surfactant self-assembly, and any attempt to understand or characterize microemulsions without a broad picture of surfactant systems will be rather meaningless. Microemulsions are, in contrast to (macro)emulsions, thermodynamically stable single-phase systems. They are isotropic solutions, like micellar solutions, with no long-range order. Microstructures of surfactant self-assembly systems show an enormous degree of polymorphism. We may classify structures in three ways (see Figs. 1 and 2): Phases that possess long-range order and periodicity and those that do not.Monolayer and bilayer structures.Phases with discrete surfactant self-assemblies and phases that have self-assemblies that are infinite in one, two, or three dimensions.
Characteristics of Polymers and Polymerization Processes
Published in Manas Chanda, Plastics Technology Handbook, 2017
Microemulsions form upon simple mixing of the components and do not require the high-shear conditions generally used to make ordinary (macro) emulsions. Besides the optical clarity (or translucency) of a microemulsion and the small (10–50 nm) droplet size of the dispersed phase, an additional feature that distinguishes it from ordinary emulsions is that the average drop size does not grow with time owing to thermodynamic stability.
The Chemistry of Metalworking Fluids
Published in Jerry P. Byers, Metalworking Fluids, Third Edition, 2018
When diluted, an emulsifiable fluid will typically form an opaque macroemulsion similar in appearance to milk. The macroemulsion represents the dispersion of stable oil droplets in a water medium and is known as an oil-in-water or o/w emulsion. The average particle size of an oil droplet in an emulsifiable oil is greater than one micron (see Figure 7.1).
Microemulsion fuel formulation from used cooking oil with carbinol as the dispersion phase
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
This study analyzes the fuel properties of the prepared emulsion using the used UCO as the oil phase, butan-2-ol as the cosurfactant, and carbinol as the dispersed phase. Secondary butyl alcohol acting as a cosurfactant is found to quench the effect of surfactant and produce a thermodynamically stable emulsion. UCO was selected as the base oil based on the fact that it will drastically reduce the cost of fuel production as it, in most cases available free of cost since it is a waste product available at most cooking outlets. It also promotes the concept of waste-to-energy conversion. Carbinol, being the lowest molecular weight alcohol, will help to reduce the viscosity of UCO. Butan-2-ol was selected as the surface active agent based on its hydrophilic–lipophilic balance, low viscosity compared, and its advantage of being free from nitrogen and sulfur compared to commercial surfactants. Mixing of the selected oil and alcohol in the presence of the surface active agent results in the formation of an emulsion fuel. When droplets of the obtained emulsion have a diameter of above 400 nm, the dispersion is called macroemulsion, and for microemulsions, it has droplets with a diameter of 1 to 100 nm. These dispersions are comparable in terms of composition.
Synthesis of monodisperse, re-dispersable polymer particles by one-step high solid emulsion polymerization in the presence of reactive surfactant
Published in Journal of Dispersion Science and Technology, 2019
Baijun Liu, Yang Bai, Chunfu Sun, Ming Chen, Zhichen Cao, Shuai Du, Lu Xu, Mingyao Zhang
Different from traditional soap-free macroemulsion polymerization, emulsion polymerization in presence of surfmer can be accomplished in shorter periods than true surfactant-free macroemulsion polymerization.[5] The nucleation mechanism of the macroemulsion polymerization of MMA in the presence of surfmer was considered as homogeneous nucleation.[21–23] The surfmer molecules were rapid consumed in the particle formation stage; moreover these surfmer molecules hardly formed micelles in water during polymerization reaction process. The detail particle formation can be described using these steps as following scheme diagram as shown in Scheme 1. The water-soluble initiator KPS was decomposed in water into initiator radicals, which then reacted with MMA monomer and surfmer in water to form oligomeric radicals. Due to the relatively high solubility of MMA and surfmer, the oligomeric radicals hardly precipitated in water unless high critical chain lengths (CCL) were obtained. In addition, the surfmer molecules were also reacted with MMA molecules, and further prolonged the length of CCL. During this period, the surfmer molecules were rapidly consumed. Afterwards, the oligomeric radicals precipitated in water would coagulate with each other to form primary particles. The primary particle coagulated with each other for forming true particles. The surfmer molecules copolymerized into main chain provided electrostatic repulsive forces to stabilize the primary particles. As surfmer concentrations rose, the particle number formed by homogeneous nucleation increased, resulting in higher polymerization reaction rates. Duracher et al. investigated macroemulsion polymerization of styrene (St) using N-iso-propyl acrylamide (NIPAM) as surfmer and confirmed particle nucleation mechanism based on homogeneous nucleation.[24] Compared to styrene, MMA as a hydrophilic monomer would be more suitable for homogeneous nucleation mechanism in macroemulsion polymerization of MMA. On the other hand, considering the aqueous phase kinetic reactions, the initiator KPS and surfmer dissolved in water should increase the reactivity of surfmer when compare to MMA. Hence, the oligomeric radicals formed in early nucleation period should contain more surfmer units. This would enhance heterogeneity of the copolymers formed in water and promote residual MMA monomer polymerization in the formed nuclei's core. In many reports, particles prepared by surfmer as surfactant contained hydrophilic polymer-rich dense core with diffuse hydrophilic surfmer-rich shell.[25]