Polymer chemistry Polymer chemistry An addition polymer is a polymer which is formed by an addition reaction, where many monomers bond together via rearrangement of bonds without the loss of any atom or molecule. This is in contrast to a condensation polymer which is formed by a condensation reaction where a molecule, usually water, is lost during the formation. ...more on Wikipedia about "Addition polymer"
Addition polymerization, also called polyaddition or chain growth polymerization, is a polymerization technique where monomer molecules add on to a growing polymer chain one at a time. ...more on Wikipedia about "Addition polymerization"
Alternating copolymers are polymers which have properities intermediate to those of the corresponding homopolymers A and B. ...more on Wikipedia about "Alternating polymer"
ATRP or Atom Transfer Radical Polymerization is a polymerization reaction involving free radicals. It was introduced as an extension to ATRA or Atom Transfer Radical Addition by Matyjaszewski et al (1995). As a living radical polymerization which is a form of living polymerization, it allows the reaction to be carried out in a controlled way, and can be used to obtain polymers with high molecular weight and low polydispersity index. ...more on Wikipedia about "ATRP (chemistry)"
Azobisisobutyronitrile, also azobisisobutylonitrile, is a toxic white crystalline compound often used as a foamer in plastics and rubber. It is commonly known as AIBN, it decomposes by the elimination of a molecule of nitrogen gas to form two 2-cyanoprop-2-yl radicals:
...more on Wikipedia about "Azobisisobutylonitrile"
Bioplastics are a form of plastics derived from plant sources such as soy bean oil and corn starch rather than traditional plastics which are derived from petroleum. This is regarded as a much more sustainable activity, as it relies considerably less on fossil fuel imports and produces less greenhouse emissions, producing between 0.8 and 3.2 tonnes of carbon dioxide less per tonne of bioplastics vs. the same weight in petroleum based plastics. In addition, bioplastics are truly Biodegradable, as opposed to what is traditionally refered to as "biodegradable plastic", which is derived from petroleum and is mixed with heavy metals which will cause polyethylene to break down. ...more on Wikipedia about "Bioplastic"
In polymer chemistry, branching occurs by the replacement of a substituent, e.g, a hydrogen atom, on a monomer subunit, by another covalently bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type. In crosslinking rubber by vulcanization, short sulfur branches link polyisoprene chains (or a synthetic variant) into a multipy-branched thermosetting elastomer. Rubber can also be so completely vulcanized that it becomes a rigid solid, so hard it can be used as the bit in a smoking pipe. Polycarbonate chains can be crosslinked to form the hardest, most impact-resistant thermosetting plastic, used in safety glasses. ** ...more on Wikipedia about "Branching (chemistry)" It's real shortopedia feeling!
In step-growth polymerization, Carother's equation gives the number-average degree of polymerization, Xn, for a given fractional monomer conversion, p. ...more on Wikipedia about "Carother's equation"
Coordination polymerization is a form of addition polymerization in which monomer adds to a growing macromolecule through an organometallic active center. The development of this polymerization technique started in the 1950s with heterogeneous Ziegler-Natta catalysts based on titanium tetrachloride and an aluminium co-catalyst such as methylaluminoxane. ...more on Wikipedia about "Coordination polymerization"
In chemistry, copolymerization is the process of using more than one monomer in the production of a polymer, resulting in a product with properties different to the homopolymer of either monomer. The resulting product may be a random copolymer, an alternating copolymer, or a block copolymer. In the copolymerization between two monomers, M1 and M2, the following reactions may occur: ...more on Wikipedia about "Copolymerization"
Cross-links are covalent bonds linking one polymer chain to another They are the characteristic property of thermosetting plastics materials. In biology, cross-linking has applications in forming polyacrylamide gels for gel electrophoresis and in protein studies. Crosslinking inhibits close packing of the polymer chains, preventing the formation of crystalline regions. The restricted molecular mobility of a crosslinked structure limits the extension of the polymer material under loading. ...more on Wikipedia about "Cross-link"
Cyamelide is an amorphous white solid (HNCO)x and is the polymerisation product of cyanic acid together with its cyclic trimer cyanuric acid. ...more on Wikipedia about "Cyamelide"
A dendrimer is a molecule with a form like the branches of a tree. The name comes from the Greek dendra, meaning "tree." In 1979, the first dendrimer was synthesized by D.A. Tomalia and other researchers at the Dow Chemical Company, and dendrimers have been studied all over the world because their form is unique (Fig. 1). ...more on Wikipedia about "Dendrimer"
Dentine bonding agents are resin materials used to make a composite filling material adhere to the dentin. The term Dentine bonding agent is almost obsolete with the advent of newer materials which bond to both dentin and enamel. ...more on Wikipedia about "Dentine bonding agents"
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Emulsion polymerization is a type of polymerization that takes place in an emulsion typically incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water. Water soluble polymers, such as certain polyvinyl alcohols or hydroxyethyl celluloses, can also be used to act as emulsfiers/stabilisers. ...more on Wikipedia about "Emulsion polymerization"
Flory-Huggins solution theory is a mathematical model of the thermodynamics of polymer solutions which takes account of the great dissimilarity in molecular sizes in adapting the usual expression for the entropy of mixing. The result is an equation for the Gibbs free energy change for mixing a polymer with a solvent. Although it makes simplifying assumptions, it generates useful results for interpreting experiments. Paul Flory and Maurice Huggins were American physical chemists, and Flory received the Nobel Prize in Chemistry for this work in 1974. They developed the theory independently while Flory was working for Esso and Huggins was working for Kodak. ...more on Wikipedia about "Flory-Huggins solution theory"
A material’s glass transition temperature, Tg, is the temperature below which molecules have little relative mobility. Tg is usually applicable to wholly or partially amorphous phases such as glasses and plastics. For inorganic or mineral glasses, such as common silicon dioxide (SiO2) glass, it is the mid-point of a temperature range in which they gradually become more viscous and change from being liquid to solid. Thermoplastic (non- crosslinked) polymers are more complex because, in addition to a melting temperature, Tm, above which all their crystalline structure disappears, such plastics have a second, lower Tg below which they become rigid and brittle, and can crack and shatter. Small molecular weight pure substances such as water have just one such condensed-phase temperature, below which they are solid crystals (or Amorphous ice if cooled below Tg fast enough) and above which they are liquids. ...more on Wikipedia about "Glass transition temperature"
An ideal chain (or freely-jointed chain) is the simplest model to describe a polymer. It only assumes a polymer as a random walk and neglects any kind of interactions among monomers. Although it is simple, its generality gives us some insights about the physics of polymers. ...more on Wikipedia about "Ideal chain"
In chemistry initiation is a chemical reaction that triggers one or more secondary reactions. Often the initiation reaction generates a reactive intermediate from a stable molecule which is then involved in secondary reactions. In polymerisation, initiation is followed by a chain reaction and termination. ...more on Wikipedia about "Initiation (chemistry)"
Isotactic polymers refer to those polymers formed by branched monomers that have the characteristic of having all the branch groups on the same side of the polymeric chain. The monomers are all oriented in the same way: If we represent a monomer by AB then an isotactic polymer is AB-AB-AB-AB-AB-etc. ...more on Wikipedia about "Isotactic"
Isotopomers (isotopic isomers) are isomers having the same number of each isotopic atom but differing in their positions. For example, CHCHDCH and CHCHCHD are a pair of constitutional isotopomers. An isotopomer should not be confused with an isotopologue. ...more on Wikipedia about "Isotopomers" http://www.shortopedia.com never sleeps.
A Kaminsky catalyst is a catalytic system for olefin polymerization discovered by Walter Kaminsky and coworkers in 1980. Kaminsky catalysts are based on metallocenes of group 4 transition metals with methylaluminoxane (MAO). These catalysts are a kind of Ziegler-Natta catalyst, but they are homogeneous and show extremely high activity for polymerization of olefins such as ethylene, propylene, and styrene. In addition, the use of chiral metallocenes that have bridged cyclopentadienyl rings has made possible highly stereospecific (or stereoregular) polymerization of α-olefins. For example, by using metallocene 1 for polymerization of propylene, atactic polypropylene is obtained, while C2 symmetric metallocene 2 and Cs symmetric metallocene 3 catalytic systems produce isotactic polymer and syndiotactic macromolecule, respectively. ...more on Wikipedia about "Kaminsky catalyst"
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In polymer chemistry, living polymerization is a special form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain propagation. The result is that the polymer chains grow at a more constant rate than seen in traditional chain polymerization and their lengths remain very similar (i.e. they have a very low polydispersity index). Living polymerization is a popular method for synthesizing block copolymers since the polymer can be synthesized in stages, each stage containing a different monomer. Additional advantages are predetermined molar mass and control over end-groups. Living polymerization in the literature is often called "living" polymerization or controlled polymerization. Living polymerization was first described by M. Szwarc in 1956 in the anionic polymerization of styrene with a alkali metal / naphthalene system in THF. He found that after addition of monomer to the initiator system that the increase in viscosity would eventually cease but that after addition of a new amount of monomer after some time the viscosity would start to increase again . ...more on Wikipedia about "Living polymerization"
Methylaluminoxane, commonly called MAO, is a white solid with the general formula (-Al(CH3)O-)n. MAO is pyrophoric, and is violently reactive with any chemical bearing an acidic proton. However, MAO is generally used as a solution in an aromatic hydrocarbon due to its relatively high solubility in such hydrocarbons. Most commonly, MAO is sold in solution with toluene but it is also soluble in similar solvents such as xylene, cumene, or mesitylene. Its solubility is largely dependant on the content of trimethylaluminium. The toluene solution is clear to cloudy and reacts with air at the surface giving off a dense smoke ...more on Wikipedia about "Methylaluminoxane"
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