Information about Apolar
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Dew drop on a hydrophobic leaf surface
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Water drops on the hydrophobic surface of grass
For other uses, see Hydrophobia
In chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of a molecule (known as a hydrophobe) that is repelled from a mass of water [1].
Hydrophobic molecules tend to be non-polar and thus prefer other neutral molecules and nonpolar solvents. Hydrophobic molecules in water often cluster together forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.
Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar from polar compounds.
Hydrophobic is often used interchangeably with "lipophilic". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions — the silicones, for instance.
Chemical background
According to thermodynamics, matter seeks to be in a low-energy state, and bonding reduces chemical energy. Water is electrically polarized, and is able to form hydrogen bonds internally, which gives it many of its unique physical properties. But, since hydrophobes are not electrically polarized, and because they are unable to form hydrogen bonds, water repels hydrophobes, in favour of bonding with itself. It is this effect that causes the hydrophobic interaction — which in itself is incorrectly named as the energetic force comes from the hydrophilic molecules.[2] Thus the two immiscible phases (hydrophilic vs. hydrophobic) will change so that their corresponding interfacial area will be minimal. This effect can be visualized in the phenomenon called phase separation.Superhydrophobicity
Superhydrophobic materials have surfaces that are extremely difficult to wet with water contact angles in excess of 150°. Many of these very hydrophobic materials found in nature rely on Cassie's law and are biphasic on the submicrometer level with one component air. The Lotus effect is based on this principle. An example of a biomimetic superhydrophobic material in nanotechnology is nanopin film. In one study [3] a vanadium pentoxide surface is presented that can switch reversibly between superhydrophobicity and superhydrophilicity under the influence of UV radiation. According to the study any surface can be modified to this effect by application of a suspension of rose-like V2O5 particles for instance with an inkjet printer. Once again hydrophobicity is induced by interlaminar air pockets (separated by 2.1 nm distances). The UV effect is also explained. UV light creates electron-hole pairs, with the holes reacting with lattice oxygen creating surface oxygen vacancies while the electrons reduce V5+ to V3+. The oxygen vacancies are met by water and this water absorbency by the vanadium surface makes it hydrophilic. By extended storage in the dark, water is replaced by oxygen and hydrophilicity is once again lost.See also
References
1. ^ Aryeh Ben-Na'im Hydrophobic Interaction Plenum Press, New York (ISBN 0-306-40222-X)
2. ^ Goss, K. U. and R. P. Schwarzenbach (2003): "Rules of Thumb for Assessing Equilibrium Partitioning of Organic Compounds: Successes and Pitfalls." JOURNAL OF CHEMICAL EDUCATION 80(4): 450-455. Link to abstract
3. ^ UV-Driven Reversible Switching of a Roselike Vanadium Oxide Film between Superhydrophobicity and SuperhydrophilicityHo Sun Lim, Donghoon Kwak, Dong Yun Lee, Seung Goo Lee, and Kilwon Cho J. Am. Chem. Soc.; 2007; 129(14) pp 4128 - 4129; (Communication) doi:10.1021/ja0692579
2. ^ Goss, K. U. and R. P. Schwarzenbach (2003): "Rules of Thumb for Assessing Equilibrium Partitioning of Organic Compounds: Successes and Pitfalls." JOURNAL OF CHEMICAL EDUCATION 80(4): 450-455. Link to abstract
3. ^ UV-Driven Reversible Switching of a Roselike Vanadium Oxide Film between Superhydrophobicity and SuperhydrophilicityHo Sun Lim, Donghoon Kwak, Dong Yun Lee, Seung Goo Lee, and Kilwon Cho J. Am. Chem. Soc.; 2007; 129(14) pp 4128 - 4129; (Communication) doi:10.1021/ja0692579
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Hydrophobia may refer to:
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- rabies, especially a set of symptoms of the later stages of an infection, in which the victim has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench his or her thirst.
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Attic Greek is the prestige dialect of Ancient Greek that was spoken in Attica, which includes Athens. Of the ancient dialects, it is the most similar to later Greek and is the standard form of the language studied in courses in "Ancient Greek".
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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Chemical polarity, also known as bond polarity or simply polarity, is a concept in chemistry which describes how equally bonding electrons are shared between atoms.
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A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. Most other commonly-used solvents are organic (carbon-containing) chemicals. These are called organic solvents.
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contact angle is the angle at which a liquid/vapor interface meets the solid surface. The contact angle is specific for any given system and is determined by the interactions across the three interfaces.
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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Alkanes, also known as Paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i.e. hydrocarbons), where each of these atoms are linked together exclusively by single bonds (i.e. they are saturated compounds) without any cyclic structure (i.
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The acronym OIL can refer to:
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- Output Input Language
- Office of Infrastructure and Logistics - Luxembourg
- Ontology Inference Layer or Ontology Interchange Language, an Ontology Infrastructure for the Semantic Web.
- Oil India Limited.
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Fat
Fat may refer to:- Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
- Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes
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Lipophilicity, fat-liking, refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene.[1] These non-polar solvents are themselves lipophilic — the axiom that like dissolves like
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Not to be confused with the element silicon.
Silicones (more accurately called polymerized siloxanes or polysiloxanes) are mixed inorganic-organic polymers with the chemical formula [R2SiO]n
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Thermodynamics (from the Greek θερμη, therme, meaning "heat" and δυναμις, dynamis, meaning "power") is a branch of physics that studies the effects of changes in temperature, pressure, and volume on
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hydrogen bond is a special type of dipole-dipole bond that exists between an electronegative atom and a hydrogen atom bonded to another electronegative atom. This type of bond always involves a hydrogen atom, thus the name.
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Hydrophile, from the Greek (hydros) "water" and φιλια (philia) "friendship," refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding.
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In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
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contact angle is the angle at which a liquid/vapor interface meets the solid surface. The contact angle is specific for any given system and is determined by the interactions across the three interfaces.
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Cassie's law describes the effective contact angle θc for a liquid on a composite surface [1]. The law explains how simply roughing up a surface increases the apparent surface angle.
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A biphasic system is one which has two phases. For example in chemistry, when oil and water are poured into a beaker, they form a biphasic system. In chronobiology, biphasic sleep
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lotus effect in material science is the observed self-cleaning property found with lotus plants. In some Eastern cultures, the lotus plant is a symbol of purity. Although lotuses prefer to grow in muddy rivers and lakes, the leaves and flowers remain clean.
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Bionics (also known as biomimetics, biognosis, biomimicry, or bionical creativity engineering) is the application of methods and systems found in nature to the study and design of engineering systems and modern technology.
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Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the atomic and molecular scale, normally 1 to 100 nanometers, and the fabrication of devices within that size range.
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Nanopin film is an experimental material in nanotechnology developed in 2005 with unusual superhydrophobic properties [1]. A droplet of water makes contact with the surface of this film and forms an almost perfect sphere with a contact angle of 178°.
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Vanadium(V) oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide
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super hydrophilicity, was discovered in 1995. Super hydrophilic material has various advantages. For example, it can defog glass, and it can also enable oil spots to be swept away easily with water.
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Suspension is a heterogenous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometre [1]. Unlike colloids, suspensions will eventually settle. An example of a suspension would be sand in water.
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Inkjet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper. They are the most common type of computer printer for the general consumer due to their low cost, high quality of output, capability of printing in vivid
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1 nanometre =
SI units
010−9 m 010−3 μm
US customary / Imperial units
010−9 ft 010−9 in
A nanometre (American spelling: nanometer, symbol nmSI units
010−9 m 010−3 μm
US customary / Imperial units
010−9 ft 010−9 in
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