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Encyclopedia > Polymerization
An example of alkene polymerisation, in which each Styrene monomer unit's double bond reforms as a single bond with another styrene monomer and forms polystyrene.

In polymer chemistry, polymerization is a process of bonding monomers, or "single units" together through a variety of reaction mechanisms to form longer chains named polymers. Polymers exist as a variety of 3-dimensional shapes[1], each with specific individual properties relevant to the monomers or reaction mechanisms they are formed from. Image File history File links Size of this preview: 800 × 198 pixelsFull resolution (1557 × 385 pixel, file size: 54 KB, MIME type: image/png) polymerization of styrene, polystyrene File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Polymerization ... Image File history File links Size of this preview: 800 × 198 pixelsFull resolution (1557 × 385 pixel, file size: 54 KB, MIME type: image/png) polymerization of styrene, polystyrene File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Polymerization ... C8H8 redirects here. ... Polystyrene is a polymer made from the monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. ... Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... A broad metal chain made of torus-shaped links. ... A polymer is a substance composed of molecules with large molecular mass consisting of repeating structural units, or monomers, connected by covalent chemical bonds. ...

Contents

Introduction

Single-monomer formed polymers
Co-polymers

In chemical compounds, polymerization occurs via a variety of reaction mechanisms which vary in complexity due to functional groups present in reacting compounds[2] and their inherent steric effects explained by VSEPR Theory. In more straightforward polymerization, alkenes, which are a relatively stable due to σ bonding between carbon atoms form polymers through relatively simple radical reactions; conversely, more complex reactions such as those that involve substitution at the carbonyl atom require more complex synthesis due to the way in which reacting molecules polymerise.[2] In organic chemistry, functional groups are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Steric effects are the interaction of molecules dictated by their shape and/or spatial relationships. ... Valence shell electron pair repulsion theory (VSEPR) (1957) is a model in chemistry that aims to generally represent the shapes of individual molecules [1] . To achieve this, it is necessary to construct a valid Lewis structure that shows all of the bonds within the molecule and the locations of lone... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ...


As alkenes can be formed in somewhat straightforward reaction mechanisms, they form useful compounds such as polyethene and polyvinyl chloride (PVC) when undergoing radical reactions[2], which are produced in high tonnages each year[2] due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. Polymers such as PVC are generally referred to as "singular" polymers as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one molecule are referred to as "co-polymers". Polyethylene or polyethene is one of the simplest and most inexpensive polymers. ... Polyvinyl chloride PVC, (IUPAC Polychloroethene) commonly abbreviated PVC, is a widely used thermoplastic polymer. ...


Other monomer units, such as formaldehyde hyrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (>-80oC) to form trimers[2]; molecules consisting of 3 monomer units which can cyclize to form ring cyclic structures, or undergo further reactions to form tetramers[2], or 4 monomer-unit compounds. Further compounds either being referred to as oligomers[2] in smaller molecules. Generally, because formaldehyde is an exceptionally reactive electrophile it allows nucleophillic addition of hemiacetal intermediates, which are compounds which are generally short lived and relatively unstable "mid stage" compounds, which react with other molecules present to form more stable polymeric compounds. Trimer might refer to: trimer (chemistry), a reaction product composed of three identical molecules trimer (biochemistry), a compound of three macromolecules non-covalently bound This is a disambiguation page: a list of articles associated with the same title. ... A tetramer is a protein with four subunits (tetrameric). ... In chemistry, an oligomer consists of a finite number of monomer units (oligo is Greek for a few), in contrast to a polymer which, at least in principle, consists of an infinite number of monomers. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ...


Chain-Growth Polymerization

Main article: Chain-growth polymerization

Addition polymerization involves the linking together of molecules incorporating double or triple chemical bonds. These unsaturated monomers (the identical molecules which make up the polymers) have extra internal bonds which are able to break and link up with other monomers to form the repeating chain. Addition polymerization is involved in the manufacture of polymers such as polyethene, polypropylene and polyvinyl chloride (PVC). A special case of addition polymerization leads to living polymerization. Addition polymerisation,also called polyaddition or chain growth polymerization, is a polymerisation technique where monomer molecules add on to a growing polymer chain one at a time. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... Polyethylene or polyethene is one of the simplest and most inexpensive polymers. ... Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap Micrograph of polypropylene Polypropylene or polypropene (PP) is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including food packaging, ropes, textiles, plastic parts... Polyvinyl chloride PVC, (IUPAC Polychloroethene) commonly abbreviated PVC, is a widely used thermoplastic polymer. ... In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . ...


Condensation polymerization occurs when monomers bond together through condensation reactions. Typically these reactions can be achieved through reacting molecules incorporating alcohol, amine or carboxylic acid (or other carboxyl derivative) functional groups. When an amine reacts with a carboxylic acid an amide or peptide bond is formed, with the release of water (hence condensation polymerization.) This is the process through which amino acids link up to form proteins, as well as how kevlar is formed. A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. ... Functional group of an alcohol molecule. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... In organic chemistry, functional groups are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Amide functional group In chemistry, an amide is one of two kinds of compounds: - the organic functional group characterized by a carbonyl group (C=O) linked to a nitrogen atom (N), or a compound that contains this functional group (pictured to the right); or - a particular kind of nitrogen anion. ... A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... Phenylalanine is one of the standard amino acids. ... Chemical structure of Kevlar. ...


The chain growth-step growth system categorizes polymers based on their mechanism. While most polymers will fall into their similar category from the addition-condensation method of categorization, there are a few exceptions.


Chain growth polymers are defined as polymers formed by the reaction of monomer with a reactive center. These polymers grow to high molecular weight at a very fast rate. It is important to note that the overall conversion rates between chain and step growth polymers are similar, but that high molecular weight polymers are formed in addition reactions much more quickly than with step polymerizations. In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... In chemistry, a reactive center is a particular location, usually an atom, within a chemical compound that is the likely center of a reaction in which the chemical is involved. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ...


Addition polymerization involves the breaking of double or triple bonds, which are used to link monomers into chains. In the polymerization of ethene (fig. 1), its pi bond is broken and these two electrons rearrange to create a new propagating center like the one that attacked it. The form this propagating center takes depends on the specific type of addition mechanism. There are several mechanisms through which this can be initiated. The free radical mechanism was one of the first methods to be used. Free radicals are very reactive atoms or molecules which have unpaired electrons. Taking the polymerization of ethene as an example, the free radical mechanism can be divided in to three stages: initiation, propagation and termination. In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...

Initiation is the creation of free radicals necessary for propagation. The radicals can be created from radical initiators, such as organic peroxide molecules, molecules containing an O-O single bond, by reacting oxygen with ethene. The products formed are unstable and easily break down into two radicals. In an ethene monomer, one electron pair is held securely between the two carbons in a sigma bond. The other is more loosely held in a pi bond. The free radical uses one electron from the pi bond to form a more stable bond with the carbon atom. The other electron returns to the second carbon atom, turning the whole molecule in to another radical. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. ... A peroxide is a compound containing an oxygen-oxygen single bond. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ...


Propagation is the rapid reaction of this radicalised ethene molecule with another ethene monomer, and the subsequent repetition to create the repeating chain.


Termination occurs when a radical reacts in a way that prevents further propagation. The most common method of termination is by coupling where two radical species react with each other forming a single molecule. Another, less common method of termination is disproportionation where two radicals meet, but instead of coupling, they exchange a proton, which gives two terminated chains, one saturated and the other with a terminal double bond.


Free radical addition polymerization of ethylene must take place at high temperatures and pressures, approximately 300°C and 2000 At. While most other free radical polymerizations do not require such extreme temperatures and pressures, they do tend to lack control. One effect of this lack of control is a high degree of branching. Also, as termination occurs randomly, when two chains collide, it is impossible to control the length of individual chains. A newer method of polymerization similar to free radical, but allowing more control involves the Ziegler-Natta catalyst especially with respect to polymer branching. A Ziegler-Natta catalyst is a reagent used in the production of unbranched, stereoregular vinyl polymers. ... Branch point in a polymer In polymer chemistry, branching occurs by the replacement of a substituent, e. ...


Other forms of addition polymerization include cationic addition polymerization and anionic addition polymerization. While not used to a large extent in industry yet due to stringent reaction conditions such as lack of water and oxygen, these methods provide ways to polymerize some monomers that cannot be polymerized by free radical methods such as polypropylene. Cationic and anionic mechanisms are also more ideally suited for living polymerizations, although free radical living polymerizations have also been developed. An anionic addition polymerization of vinyl monomers is initiated by a strong base, such as an alkali amide, or an organometallic compound, such as n-butyllithium. ... Polypropylene lid of a Tic Tacs box, with a living hinge and the resin identification code under its flap Micrograph of polypropylene Polypropylene or polypropene (PP) is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including food packaging, ropes, textiles, plastic parts... In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed . ...


Step-Growth Polymerization

Main article: Step-growth polymerization

Step growth polymers are defined as polymers formed by the stepwise reaction between functional groups of monomer. Most step growth polymers are also classified as condensation polymers, but not all step growth polymers (like polyurethanes formed from isocyanate and alcohol bifunctional monomers) release condensates. Step growth polymers increase in molecular weight at a very slow rate at lower conversions and only reach moderately high molecular weights at very high conversion (i.e. >95%). Step-growth polymerization is a polymerization process that involves a chemical reaction between multifunctional monomer molecules. ... A polyurethane is any polymer consisting of a chain of organic units joined by urethane links. ... Isocyanate is the chemical group of atoms -N=C=O (1 nitrogen, 1 carbon, 1 oxygen), as opposed to cyanate, -O-C≡N, which is formed from cyanogen in the normal -ate manner. ...


To alleviate inconsistencies in these naming methods, adjusted definitions for condensation and addition polymers have been developed. A condensation polymer is defined as a polymer that involves elimination of small molecules during its synthesis, or contains functional groups as part of its backbone chain, or its repeat unit does not contain all the atoms present in the hypothetical monomer to which it can be degraded. An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In polymer chemistry, a structural unit is a building block of a polymer chain. ...


DNA Polymerization

Main article: DNA polymerase

DNA polymerization is a description of DNA polymerization using the enzyme DNA polymerase. This is not the synthetic, purely chemical, laboratory method of artificially synthesizing oligos in a laboratory or oligo factory. Artificially synthesized oligos are a key aspect of the Polymerase Chain Reaction (PCR). 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ...


See also

Plasma polymerization uses plasma sources to generate a gas discharge that provides energy to activate or fragment gaseous or liquid monomer, often containing a vinyl group, in order to initiate polymerization. ... A Ziegler-Natta catalyst is a reagent used in the production of unbranched, stereoregular vinyl polymers. ... In chemistry, and in particular, in organometallic chemistry, a metallocene is a compound consisting of an aromatic organic ligand bound to a metal. ...

Notes

  1. ^ International Union of Pure and Applied Chemistry, et al. (2000) "Gold Book"
  2. ^ a b c d e f g Clayden, J., Greeves, N. et al (2000), p1450-1466

References

  1. International Union of Pure and Applied Chemistry, et al. (2000) "IUPAC Gold Book" Retrieved on 11th May 2007 from "IUPAC Gold Book" on http://goldbook.iupac.org/
  2. Clayden, J., Greeves, N. et al (2000). "Organic chemistry" Oxford

  Results from FactBites:
 
Experimental Investigations in Polymerization Kinetics (3336 words)
This requires the measurement of the overall rate of polymerization as a function of monomer concentration; accordingly varying amounts of monomer had to be replaced by an inert solvent.
With respect to polymerization kinetics they have a lot in common with normal emulsion polymerization the most characteristic feature of which is their ability to "separate" the radicals growing in micelles or latex particles from each other thus suppressing termination to a high extent and -- as a consequence -- providing high rates of polymerization.
The site of polymerization in emulsions and microemulsions are (at least to predominantly) these micelles and (micro-)latex particles where according to the specific recipe of preparing microemulsions the various concentrations (monomer, coemulsifier, partly also solvent) are not really known with confidence.
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