In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them. These surrounded solute particles then move away from the solid solute and out into the solution. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution usually has the state of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. One important parameter of a solution is the concentration, which is a measure of the amount of solute in a given amount of solution or solvent. The term "aqueous solution" is used when one of the solvents is water.
Sodium dodecyl sulfate (SDS) or sodium lauryl sulfate (SLS), sometimes written sodium laurilsulfate, is an organic compound with the formula CH3(CH2)11OSO3Na and structure H3C−(CH2)11−O−S(=O)2−O−Na+. It is an anionic surfactant used in many cleaning and hygiene products. This compound is the sodium salt of the 12-carbon organosulfate. Its hydrocarbon tail combined with a polar "headgroup" give the compound amphiphilic properties that make it useful as a detergent. SDS is also component of mixtures produced from inexpensive coconut and palm oils. SDS is a common component of many domestic cleaning, personal hygiene and cosmetic, pharmaceutical, and food products, as well as of industrial and commercial cleaning and product formulations.
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more soluble in hard water, because the polar sulfonate is less likely than the polar carboxylate to bind to calcium and other ions found in hard water.
Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. Surfactants may function as emulsifiers, wetting agents, detergents, foaming agents, or dispersants. The word "surfactant" is a blend of surface-active agent, coined c. 1950.
Emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer are emulsified in a continuous phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers. The name "emulsion polymerization" is a misnomer that arises from a historical misconception. Rather than occurring in emulsion droplets, polymerization takes place in the latex/colloid particles that form spontaneously in the first few minutes of the process. These latex particles are typically 100 nm in size, and are made of many individual polymer chains. The particles are prevented from coagulating with each other because each particle is surrounded by the surfactant ('soap'); the charge on the surfactant repels other particles electrostatically. When water-soluble polymers are used as stabilizers instead of soap, the repulsion between particles arises because these water-soluble polymers form a 'hairy layer' around a particle that repels other particles, because pushing particles together would involve compressing these chains.
A micelle or micella is an aggregate of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension. A typical micelle in water forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre.
The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in an aqueous solution and exclude water molecules. The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes hydrogen bonding between molecules of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. A positive free energy change of the surrounding solvent indicates hydrophobicity, whereas a negative free energy change implies hydrophilicity.
Ethoxylation is a chemical reaction in which ethylene oxide adds to a substrate. It is the most widely practiced alkoxylation, which involves the addition of epoxides to substrates.
Krafft temperature is defined as the minimum temperature from which the micelle formation takes place. It is named after German chemist Friedrich Krafft. It has been found that solubility at the Krafft point is nearly equal to critical micelle concentration (CMC). Below the Krafft temperature, the maximum solubility of the surfactant will be lower than the critical micelle concentration, meaning micelles will not form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in an aqueous solution. Visually the effect of going below the Krafft point is similar to that of going above the cloud point, with the solution becoming cloudy or opaque due to the surfactant molecules undergoing flocculation.
Micellar electrokinetic chromatography (MEKC) is a chromatography technique used in analytical chemistry. It is a modification of capillary electrophoresis (CE), extending its functionality to neutral analytes, where the samples are separated by differential partitioning between micelles and a surrounding aqueous buffer solution.
In colloidal and surface chemistry, the critical micelle concentration (CMC) is defined as the concentration of surfactants above which micelles form and all additional surfactants added to the system will form micelles.
Cetrimonium bromide ([(C16H33)N(CH3)3]Br; cetyltrimethylammonium bromide; hexadecyltrimethylammonium bromide; CTAB) is a quaternary ammonium surfactant.
CHAPS is a zwitterionic surfactant used in the laboratory to solubilize biological macromolecules such as proteins. It may be synthesized from cholic acid and is zwitterionic due to its quaternary ammonium and sulfonate groups; it is structurally similar to certain bile acids, such as taurodeoxycholic acid and taurochenodeoxycholic acid. It is used as a non-denaturing detergent in the process of protein purification and is especially useful in purifying membrane proteins, which are often sparingly soluble or insoluble in aqueous solution due to their native hydrophobicity.
Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene flanked by two hydrophilic chains of polyoxyethylene. The word poloxamer was coined by BASF inventor, Irving Schmolka, who received the patent for these materials in 1973. Poloxamers are also known by the trade names Pluronic, Kolliphor, and Synperonic.
Micellar liquid chromatography (MLC) is a form of reversed phase liquid chromatography that uses an aqueous micellar solutions as the mobile phase.
Docusate is the common chemical and pharmaceutical name of the anion bis(2-ethylhexyl) sulfosuccinate, also commonly called dioctyl sulfosuccinate (DOSS). It is on the World Health Organization's List of Essential Medicines. Salts of this anion, especially docusate sodium, are widely used in medicine as laxatives and as stool softeners, by mouth or rectally. In 2020, it was the 163rd most commonly prescribed medication in the United States, with more than 3 million prescriptions. Some studies claim that docusate is not more effective than a placebo for improving constipation. Other docusate salts with medical use include those of calcium and potassium.
In colloidal chemistry, the surfactant’s critical micelle concentration (CMC) plays a factor in Gibbs free energy of micellization. The exact concentration of the surfactants that yield the aggregates being thermodynamically soluble is the CMC. The Krafft temperature determines the solubility of the surfactants which in turn is the temperature that CMC is achieved. There are many parameters that affect the CMC. The interaction between the hydrophilic heads and the hydrophobic tails play a part, as well as the concentration of salt within the solution and surfactants.
The behavior of quantum dots (QDs) in solution and their interaction with other surfaces is of great importance to biological and industrial applications, such as optical displays, animal tagging, anti-counterfeiting dyes and paints, chemical sensing, and fluorescent tagging. However, unmodified quantum dots tend to be hydrophobic, which precludes their use in stable, water-based colloids. Furthermore, because the ratio of surface area to volume in a quantum dot is much higher than for larger particles, the thermodynamic free energy associated with dangling bonds on the surface is sufficient to impede the quantum confinement of excitons. Once solubilized by encapsulation in either a hydrophobic interior micelle or a hydrophilic exterior micelle, the QDs can be successfully introduced into an aqueous medium, in which they form an extended hydrogel network. In this form, quantum dots can be utilized in several applications that benefit from their unique properties, such as medical imaging and thermal destruction of malignant cancers.
In chemistry, cosolvents are substances added to a primary solvent in small amounts to increase the solubility of a poorly-soluble compound. Their use is most prevalent in chemical and biological research relating to pharmaceuticals and food science, where alcohols are frequently used as cosolvents in water to dissolve hydrophobic molecules during extraction, screening, and formulation. Cosolvents find applications also in environmental chemistry and are known as effective countermeasures against pollutant non-aqueous phase liquids, as well as in the production of functional energy materials and synthesis of biodiesel.
