In polymer chemistry, living polymerization is a form of addition polymerization where the ability of a growing polymer chain to terminate has been removed ^[1]. 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 ^[2]. Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules. ... 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. ... A polymer is a long, repeating chain of atoms, formed through the linkage of many molecules called monomers. ... 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. ... 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. ... 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. ... 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. ... The reaction rate for a reactant or product in a particular reaction is defined as the amount of the chemical that is formed or removed (in moles or mass units) per unit time per unit volume. ... Polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains [1]. There are many forms of polymerization and different systems exist to categorize them. ... ɛIn organic chemistry, the polydispersity index (PDI), is a measure of the distribution of molecular weights in a ngfhdfgdswetretretrerertetretreretrererereyr65r67576tghhhjjkhoj; ]l ]o0i o0i ki][ 8i jko[8i ô × ¹ ² ³ ‘ “ ’ ” ¢ £ € ¥ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω ʈ ɖ ɟ ɡ ɢ ʡchains approach uniform chain length, the PDI approaches unity (1). ... A heteropolymer, also called a copolymer, is a polymer formed when two different types of monomer are linked in the same polymer chain. ... 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. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... An end-group in polymer chemistry is a constitutional unit that is an extremity of a macromolecule or oligomer molecule. ... Styrene (also vinyl benzene, ethenylbenzene, phenethylene or phenylethene, cinnamene, diarex HF 77, styrolene, styrol, styropol) is an organic compound which is an aromatic hydrocarbon having the chemical formula C8H8. ... The alkali metals are the series of elements in Group 1 (IUPAC style) of the periodic table (excluding hydrogen in all but one rare circumstance): lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). ... Naphthalene (also known as naphthalin, naphthaline, tar camphor, white tar, albocarbon, or naphthene) is a crystalline, aromatic, white, solid hydrocarbon, best known as the primary ingredient of mothballs. ... The pitch drop experiment at the University of Queensland. ...

The main living polymerization techniques are:

• living cationic polymerization
• ring opening metathesis polymerization
• group transfer polymerization
• anionic living polymerization
• free radical living polymerization
• living Ziegler-Natta polymerization

Anionic living polymerization

Living polymerization was first demonstrated by Szwarc through the anionic polymerization of styrene in THF using sodium naphtalenide as initiator. 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. ... Styrene (also vinyl benzene, ethenylbenzene, phenethylene or phenylethene, cinnamene, diarex HF 77, styrolene, styrol, styropol) is an organic compound which is an aromatic hydrocarbon having the chemical formula C8H8. ... Tetrahydrofuran, also known as THF, hydrofuran, oxolane, oxacyclopentane, or furanidine, is a heterocyclic organic compound. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ...

Free radical living polymerization

Very late in the twentieth century several new methods were discovered which allowed the development of living polymerization using free radical chemistry. These techniques involved catalytic chain transfer agent (CCT), the iniferter mediated polymerization, stable free radical mediated polymerization (SFRP), atom transfer radical polymerization (ATRP)and reversible addition-fragmentation chain transfer (RAFT) polymerization. For other uses, see radical. ... CCT can stand for: Cobb Community Transit Caring Cancer Trust Central California Traction Company, railroad in California, AAR reporting marks CCT Certificate of Completion of Training (CCT), which doctors in the UK receive on completion of their specialist training Correlated color temperature Cognitive Complexity Theory Computational complexity theory Clean Coal... RAFT or Reversible Addition-Fragmentation chain Transfer is a form of living radical polymerization. ...

Catalytic chain transfer polymerization

Although not a strictly living form of polymerization catalytic chain transfer polymerization must be mentioned as it figures significantly in the development of later forms of living free radical polymerization polymerization. Discovered in the late 1970's in the USSR it was found that cobalt porphyrins where able to reduce the molecular weight during polymerization of methacrylates. General Name, Symbol, Number cobalt, Co, 27 Chemical series transition metals Group, Period, Block 9, 4, d Appearance metallic with gray tinge Atomic mass 58. ... A porphyrin is a heterocyclic macrocycle made from 3 pyrrole subunits and one pyrroline subunit, and linked on opposite sides through 4 methine bridges. ... 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). ... Polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains [1]. There are many forms of polymerization and different systems exist to categorize them. ... Methyl methacrylate is a chemical compound mostly known as monomer for the production of the transparent plastic polymethyl methacrylate (PMMA). ...

Later investigations showed that the cobalt glyoxime complexes were as effective as the porphyrin catalysts and also less oxygen sensitive. Due to the high oxygen sensitivity these catalyst have been investigated much more thoroughly than the porphyrin catalysts.

The major products of catalytic chain transfer polymerization are vinyl terminated polymer chains. One of the major drawbacks of the process is that catalytic chain transfer polymerization does not produce macromonomers but instead produces addition fragmentation agents. When a growing polymer chain reacts with the addition fragmentation agent the radical end-group attacks the vinyl bond and forms a bond. However the resulting product is so hindered that the species undergoes fragmentation, leading eventually to telechelic species. Vinyl products (such as these records) come in many colors. ... An end-group in polymer chemistry is a constitutional unit that is an extremity of a macromolecule or oligomer molecule. ... Steric effects are the interaction of molecules dictated by their shape and/or spatial relationships. ... A telechelic polymer is a polymer carrying functionalised endgroups. ...

These addition fragmentation chain transfer agents do form graft copolymers with styrenic and acrylate species however they do so by first forming block copolymers and then incorporating these block copolymers into the main polymer backbone. A graft copolymer has polymer chains of one kind growing out of the sides of polymer chains with a different chemical composition. ... Styrene (also vinyl benzene, ethenylbenzene, phenethylene or phenylethene, cinnamene, diarex HF 77, styrolene, styrol, styropol) is an organic compound which is an aromatic hydrocarbon having the chemical formula C8H8. ... Acrylate monomers are esters that contain vinyl groups, that is, two carbon atoms double bonded to each other, directly attached to the carbonyl carbon. ... A heteropolymer, also called a copolymer, is a polymer formed when two different types of monomer are linked in the same polymer chain. ...

While high yields of macromonomers are possible with methacrylate monomers, low yields are obtained when using catalytic chain transfer agents during the polymerization of acrylate and stryenic monomers. This has been seen to be due to the interaction of the radical centre with the catalyst during these polymerization reactions. The reversible reaction of the cobalt macrocycle with the growing radical is known as cobalt carbon bonding and in some cases leads to a form of living polymerization. Yield in chemistry, also known as chemical yield and reaction yield, is the amount of product obtained in a chemical reaction. ... 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 reversible reaction is a chemical reaction that may proceed in both the forward and reverse directions. ... A macrocycle is, as defined by IUPAC, In the chemical literature, organic chemists may consider any molecule containing a ring of seven, fifteen, or any arbitrarily large number of atoms to be macrocyclic. ...

Iniferters

Iniferters are chemicals that act as initiators and transfer agents, and terminators in free radical reactions, the most common of these agents are the dithiuram type. Another meaning of initiator is SCSI initiator. ...

Stable free radical mediated polymerization

Often called nitroxide mediated polymerization (NMP), SFRP was discovered while using a radical scavenger called TEMPO when investigating the rate of initiation during free radical polymerization. When the coupling of the stable free radical with the polymeric radical is sufficiently reversible, termination is reversible, and the propagating radical concentration can be limited to levels that allow controlled polymerization. Similar to atom transfer radical polymerization (discussed below), the equilibrium between dormant chains (those reversibly terminated with the stable free radical) and active chains (those with a radical capable of adding to monomer) is designed to heavily favor the dormant state. NMP can be: The New Millennium Program, a spaceflight technology initiative at NASA. NMP, a defunct minor political party in New Zealand. ... A scavenger is a substance added to a mixture in order to remove or inactivate impurities or unwanted reaction products. ... In musical terminology, tempo (Italian for time) is the speed or pace of a given piece. ... The reaction rate for a reactant or product in a particular reaction is defined as the amount of the chemical that is formed or removed (in moles or mass units) per unit time per unit volume. ...

Atom transfer radical polymerization

Atom transfer radical polymerization or ATRP involves the chain initiation of free radical polymerization by a halogenated organic species in the presence of a metal halide species. The metal has a number of different oxidation states that allows it to abstract a halide from the organohalide, creating a radical that then starts free radical polymerization. After inititation and propagation, the radical on the chain active chain terminus is reversibly terminated (with the halide) by reacting with the catalyst in its higher oxidation state. Thus, the redox process causes gives rise to an equilibrium between dormant (Polymer-Halide) and active (Polymer-radical) chains. The equlibrium is designed to heavily favor the dormant state, which effectively reduces the radical concentration to sufficiently low levels to limit bimolecular coupling. ATRP or Atom Transfer Radical Polymerization is a polymerization reaction involving free radicals. ... 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. ... The halogens The halogens are a chemical series. ... Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary. ... In chemistry, the oxidation state is a measure of the degree of oxidation of an atom in a chemical compound. ...

Obstacles associated with this type of reaction is the generally low solubility of the metal halide species, which results in limited availability of the catalyst. This is improved by the addition of a ligand, which significantly improves the solubility of the metal halide and thus the availability of the catalyst but complicates subsequent catalyst removal from the polymer product. In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with one or more central atoms or ions (these ligands act as a...

Reversible Addition Fragmentation chain Transfer (RAFT) polymerization

Reversible Addition Fragmentation chain Transfer polymerization or RAFT is a degenerative chain transfer process and is free radical in nature. Most RAFT agents contain thiocarbonyl-thio groups, and it is the reaction of polymeric and other radicals with the C=S that leads to the formation of stabilized radical intermediates. In an ideal system, these stabilised radical intermediates do not undergo termination reactions, but instead reintroduce a radical capable of reinitiation or propagation with monomer, while they themselves reform their C=S bond. The cycle of addition to the C=S bond, followed by fragmentation of a radical, continues until all monomer is consumed. Termination is limited in this system by the low concentration of active radicals. RAFT, invented by Rizzardo et al. at CSIRO and a mechanistically identical process termed Macromolecular Designvia Interchange of Xanthates (MADIX), invented by Zard et al. at Rhodia were both first reported in 1998/early 1999. RAFT or Reversible Addition-Fragmentation chain Transfer is a form of living radical polymerization. ... The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is the national government body for scientific research in Australia. ...

External links

• IUPAC Gold Book Definition
• precise definitions from the American Chemical Society
• Living Ziegler-Natta Polymerization Article
• Living polymers 50 years of evolution Article

The Gold Book or Compendium of Chemical Terminology (ISBN 0865426848) is a book published by IUPAC containing internationally accepted definitions for terms in chemistry. ...

References

1. ↑  M. Szwarc, Nature 1956, 176, 1168.
2. ↑  Szwarc, M.; Levy, M.; Milkovich, R. J. Am. Chem. Soc. 1956, 78, 2656