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The article contains sections titled: 1. Historical Review 2. Physical Chemistry of the Washing Process 2.1. Introduction to the Washing Process 2.2. Components 2.2.1. Substrates 2.2.2. Washing Liquid/Water 2.2.3. Soils 2.3. Wetting/Adsorption on Surfaces 2.3.1. Wetting 2.3.2. Drainage 2.3.3. Adsorption Layer 2.4. Soil Removal and Stabilization 2.4.1. Builders 2.4.1.1. Overview on Builder Systems 2.4.1.2. Precipitation Builders 2.4.1.3. Complexing Agents 2.4.1.4. Ion Exchangers 2.4.1.5. Cobuilders 2.4.1.6. Soluble Builders 2.4.2. Oily Soil 2.4.3. Particulate Soil 2.4.4. Chemical Reactions 2.4.4.1. Bleachable Stains 2.4.4.2. Enzymatic Soil Removal 2.4.5. Soil‐Repelling Effects 2.5. Formulation 2.5.1. Foam 2.5.2. Microemulsion 2.5.3. Phase Stability 2.5.4. Softeners 2.6. Concluding Remarks
The article contains sections titled: 1. Historical Review 2. Physical Chemistry of the Washing Process 2.1. Introduction to the Washing Process 2.2. Components 2.2.1. Substrates 2.2.2. Washing Liquid/Water 2.2.3. Soils 2.3. Wetting/Adsorption on Surfaces 2.3.1. Wetting 2.3.2. Drainage 2.3.3. Adsorption Layer 2.4. Soil Removal and Stabilization 2.4.1. Builders 2.4.1.1. Overview on Builder Systems 2.4.1.2. Precipitation Builders 2.4.1.3. Complexing Agents 2.4.1.4. Ion Exchangers 2.4.1.5. Cobuilders 2.4.1.6. Soluble Builders 2.4.2. Oily Soil 2.4.3. Particulate Soil 2.4.4. Chemical Reactions 2.4.4.1. Bleachable Stains 2.4.4.2. Enzymatic Soil Removal 2.4.5. Soil‐Repelling Effects 2.5. Formulation 2.5.1. Foam 2.5.2. Microemulsion 2.5.3. Phase Stability 2.5.4. Softeners 2.6. Concluding Remarks
Recebido em 5/3/13; aceito em 27/6/13; publicado na web em 2/8/13 CHARACTERIZATION OF LIQUID CRYSTALS BY OPTICAL MICROSCOPY IN POLYETHOXYLATED SURFACTANT-ALKANE-WATER SYSTEMS. The phase behavior of an alcohol polyethoxylated surfactant with decane and dodecane oil phase varying the water proportion from 5 to 90% to determine compositions in which the formation of liquid crystals and microemulsions ocurred was investigated. Pseudoternary phase diagrams were built to represent the regions of liquid crystals, biphases and microemulsions. Polarized light optical microscopy was used for the analysis and characterization of the separate phases. The micrographs obtained showed characteristics of hexagonal and lamellar phases of liquid crystal, isotropic phases, microemulsions and vesicles. This study is important to propose hypothesis regarding the factors determining the formation and stability of phases composed by surfactant/oil/water systems.Keywords: optical microscopy; liquid crystal; alcohol polyethoxylated. INTRODUCCIÓNLos surfactantes o tensoactivos en sistemas agua/aceite forman una gran variedad de estructuras de autoasociación entre las cuales se pueden mencionar las microemulsiones y los cristales líquidos. 1Una microemulsión es un fluido isotrópico, de baja viscosidad y termodinámicamente estable en la cual cantidades proporcionadas de dos fases inmiscibles (como agua y aceite) están dispersas en una sola fase por adición de una cantidad apropiada de un surfactante. Las microemulsiones están formadas por gotas con diámetros mayores a 100 nm, y tanto las tipo agua en aceite (w/o) como aceite en agua (o/w) se pueden obtener con un mismo surfactante, pero variando la composición de las fases inmiscibles, el ambiente fisicoquímico o la temperatura.2 Las microemulsiones han sido extensamente estudiadas, y se han reportado una variedad de investigaciones relacionadas con su composición, propiedades y estructuras.3 Algunos autores indican que esta fase puede ser obtenida a partir de otra con propiedades particulares, como los cristales líquidos. 4,5 Los cristales líquidos, conocidos también como mesofases, fases intermedias o semisóli-dos, poseen una estructura con un grado de orden intermedio a nivel molecular entre los líquidos y los sólidos cristalinos. A diferencia de los líquidos ordinarios, en los cristales líquidos las moléculas o iones que los forman se disponen de manera relativamente ordenada, dando origen a un estado mesomórfico que poseen un orden de largo alcance en lo que respecta a la orientación molecular y un orden parcial, o bien desorden, en lo referente a la posición de las moléculas.6 En el caso de los surfactantes, las moléculas individuales dentro de la mesofase poseen una orientación restringida y una libertad relativa de movimiento, y pueden originar cristales líquidos termotrópicos y liotrópicos. Los primeros dependen del efecto de la temperatura sobre la formación del tipo de mesofase, mientras que los cristales líquidos liotrópicos se presentan en un cierto intervalo de temperatura y ...
Contact experiments have been performed between an onion lamellar phase and brine, in the SDS/octanol/brine system. Using video microscopy we have studied the nonequilibrium behaviour of the swelling and dissolution process of onions. Experiments at T = 20 • C and 30 • C showed that temperature has a strong effect on their behaviour. At low temperature onions are observed to diffuse away from the onion phase and only swell sightly. However by increasing the temperature we induce the formation of sponge phase (L 3 ) at the onion/brine interface. Onions that initially swell then dissolve into L 3 phase expel a stable core which moves to the micellar phase and remains there. Over a longer period of time (several days) we have also observed coalescence leading to the formation of large onions of up to ∼ 100µm diameter. These huge onions have a radial distribution of domains, or solvent cavities, within them.
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