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Topic: Radical polymerization

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	Radical polymerization - Wikipedia, the free encyclopedia
		Radical polymerization is a type of polymerization in which the reactive center of a polymer chain consists of a radical.
		This often involves a metal-ion such as in the reaction of a ferrous ion with hydrogen peroxide to a ferric ion in which a hydroxyl radical is formed.
		Taking the polymerization of ethene as an example, the free radical reaction mechanism can be divided in to three stages: initiation, chain propagation and chain termination.
	en.wikipedia.org /wiki/Radical_polymerization (606 words)

	Living polymerization - Wikipedia, the free encyclopedia
		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.
		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.
		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.
	en.wikipedia.org /wiki/Living_polymerization (1107 words)

	Atom Transfer Radical Polymerization (Site not responding. Last check: 2007-11-01)
		Atom transfer radical polymerization is a controlled/“living” polymerization based on the use of radical polymerization to convert monomer to polymer.
		Radical polymerization, in contrast, can polymerize hundreds of monomers, can copolymerize two or more monomers, and can be performed in water as emulsions or suspensions.
		It is capable of polymerizing a wide variety of monomers, is tolerant of trace impurities (water, oxygen, inhibitor), and is readily applicable to industrial processes.
	polymer.chem.cmu.edu /Center/ATRP.html (472 words)

	[No title]
		The fullerene compound is employed to retard the premature free-radical polymerization of non-linear, readily polymerizable monomer by mixing the fullerene compound and monomer at or prior to subjecting the monomer to conditions, including conditions of elevated temperature and pressure, where the monomer is likely to encounter extraneous free radicals and undesirably polymerize.
		Thus, approximately 82% of the styrene polymerization was inhibited by the presence of 472 ppm of mixed fullerene.
		In the process of inhibiting the undesirable free-radical polymerization of a non-linear, readily polymerizable monomer under conditions where the monomer is likely to polymerize, which process comprises providing to the monomer a polymerization inhibiting, soluble quantity of a polymerization inhibitor, the improvement of using as polymerization inhibitor a fullerene compound.
	www.godunov.com /Bucky/patents-fulltext/05302681 (2786 words)

	Polymers
		Since a pi-bond in the monomer is converted to a sigma-bond in the polymer, the polymerization reaction is usually exothermic by 8 to 20 kcal/mol.
		Since carbon radicals are stabilized by substituents of many kinds, the preference for head-to-tail regioselectivity in most addition polymerizations is understandable.
		Polymerization of isobutylene (2-methylpropene) by traces of strong acids is an example of cationic polymerization.
	www.cem.msu.edu /~reusch/VirtTxtJml/polymers.htm (4183 words)

	Mediated Radical Polymerization
		In this bound state the propagating radical is stable or dormant and unable to participate in termination or chain transfer processes.
		Because none of the reported mediated radical polymerizations may be legitimately described as living but, at the same time, have some of the characteristics of living polymerization, a great variety of terminology has sprung up to describe these processes including pseudo-living, quasi-living, etc.
		The term mediated radical polymerization (MRP) is not only descriptive of a wide range of radical polymerizations carried out in the presence of agents to modify the reactivity of the propagating species but avoids the confusion associated with the terms living free radical, living radical, controlled radical polymerization and the like.
	www.polyacs.org /nomcl/pmse.medrad.html (771 words)

	NetLogo Models Library: Radical Polymerization
		Radical polymerization can be thought of as the process of agglomeration of small molecules (monomers) into chains (polymer chains) initiated by active particles (radicals).
		If there is at least one radical on the same patch as the given monomer, the monomer dies and the chain-length of the radical which "killed" it is incremented by 1;
		Although oxygen is widely used in industry as initiator of radical polymerization, scientists prefer to use other initiators in the lab, especially when the reaction has to be performed under conditions of atmospheric pressure and room temperature.
	ccl.northwestern.edu /netlogo/models/RadicalPolymerization (909 words)

	e-Polymers (Site not responding. Last check: 2007-11-01)
		The radical polymerization of styrene and n-butylacrylate has been conducted in the presence of different types of nitrones (R1-N+(O-)=C-R2 : R1 = tert-butyl group and R2 = isopropyl or phenyl group) in combination with a conventional free radical initiator such as AIBN or BPO.
		The structure of both the free radical initiator and the nitrone thus plays a key role in the kinetics and control of the radical polymerization, because it dictates the structure, the amount, and the reactivity of the in-situ formed nitroxide and/or alkoxyamine.
		However, for the control to be effective, the nitrone has to be pre-reacted with the radical initiator for 4 h at 85 C, followed by polymerization at 110 C by adding the monomer.
	www.e-polymers.org /abstract_shw.cfm?Abstract_id=1282 (327 words)

	Polymerization Reactions (Site not responding. Last check: 2007-11-01)
		As a result, ionic polymerization reactions are relatively insensitive to temperature, and can be run at temperatures as low as -70°C. Ionic polymerization therefore tends to produce a more regular polymer, with less branching along the backbone, and more controlled tacticity.
		Because the intermediates involved in ionic polymerization reactions can't combine with one another, chain termination only occurs when the growing chain reacts with impurities or reagents that can be specifically added to control the rate of chain growth.
		Ionic polymerization is therefore only used for monomers that don't polymerize by the free-radical mechanism or to prepare polymers with a regular structure.
	chemed.chem.purdue.edu /genchem/topicreview/bp/1polymer/reactions.html (991 words)

	Chemical & Engineering News: Latest News - New Radical Route To Polyolefins
		The need for a radical initiator and the polymer properties are indicative of a radical polymerization mechanism, the researchers note.
		In addition, polymerization doesn't occur when Li is trapped by crown ethers, when Li is replaced with larger alkali-metal cations, or when a ligating solvent such as tetrahydrofuran is used.
		The Li -catalyzed polymerization is "a great piece of work" and a "landmark" in the radical polymerization of unactivated terminal alkenes and acetylenes, comments chemistry professor Virgil Percec of the University of Pennsylvania.
	pubs.acs.org /cen/news/84/i17/8417notw4.html (572 words)

	Penn Department of Chemistry - Faculty (Site not responding. Last check: 2007-11-01)
		The reactivity of metal-centered radical species and organometallic derivatives are exploited in the control of radical polymerization by catalytic chain transfer and living radical polymerization.
		This new approach to obtaining living radical polymerization occurs by a degenerative transfer pathway that involves rapid interchange of polymeric radicals in the polymer with polymeric units in the organo-cobalt porphyrin complexes.
		This pathway to obtain living radical polymerization is a transition metal form of degenerative transfer that we refer to as radical interchange polymerization (RIP).
	www.sas.upenn.edu /chem/faculty/wayland/wayland.html (393 words)

	Chem 421 - Free Radical Polymerization - Chain Transfer (Site not responding. Last check: 2007-11-01)
		If the chain end radical attacks an atom on the backbone of the same or another chain, the result is a new radical that can reinitiate to form a branch.
		The chemistry is driven by the greater stability of the secondary radical that forms, compared to the primary one at the chain end.
		Polymerization media are usually thoroughly purged with inert gas to remove O
	www.chem.rochester.edu /~chem421/ct1.htm (604 words)

	Sumerlin Polymer Research Group - Controlled Radical Polymerization (Site not responding. Last check: 2007-11-01)
		Over the last decade, the progress experienced in the field of controlled radical polymerization (CRP), often called living free radical polymerization (LFRP), has allowed the preparation of polymeric materials that were previously unobtainable by existing synthetic techniques.
		Due to its potential to control the polymerization of the widest range of monomers in a variety of solvents (including water), reversible addition-fragmentation chain transfer (RAFT) polymerization is primarily being investigated.
		A particularly attractive feature of RAFT polymerizations is that control of molecular weight and polydispersity is achieved experimentally in a manner similar to that of conventional radical polymerizations (monomer + initiator) with the addition of a reversible chain transfer agent (CTA), usually a type of thiocarbonylthio ((S)C=S) compound.
	faculty.smu.edu /bsumerlin/research.htm (632 words)

	Eric Tillman, Research Areas
		The radical initiator is decomposed and incubated in the presence of a chromophore label containing one or more radically transferable hydrogen atoms, prior to the addition of monomer.
		Heat-induced cleavage of the photodimer is occurring during the polymerization, with the resulting polymers showing absorbance bands indicative of an anthracene-bound polymer.
		Plots of monomer conversion as a function of Mn displayed non-linearity, consistent with slow initiation from the bridgehead halide on the anthracene photodimer and cleavage of the centrally-bound chromophore during the reaction.
	www.departments.bucknell.edu /chemistry/tillman_research.htm (672 words)

	Current Organic Chemistry, Volume 6, No. 2, 2002
		In the propagation process, the radical is typically a polymer and the molecule is a monomer; in transfer, the molecule is a transfer agent and, in initiation, the radical is a species of low molar mass.
		It is now possible to predict the reactivity of both the radicals and the molecules by means of a revised form of the Patterns Scheme, and a review is presented here of the historical development of the state of understanding of reactivity in the various component steps in a polymerisation process propagated by radicals.
		The correlations for the cationic polymerization of alkyl vinyl ethers and the coordinated anionic polymerizations of a-olefines were rather complex and the mechanisms of polymerizations were discussed from the results.
	www.bentham.org /coc/contabs/coc6-2.htm (1009 words)

	SPI: About the Industry: Definitions of Resins
		Polypropylene is made by polymerizing propylene [CH ] and in the case of copolymers with monomers, with suitable catalysts, generally aluminum alkyl and titanium tetrachloride mixed with solvents.
		Polyvinyl acetate is a thermoplastic resin produced by the polymerization of vinyl acetate monomer [CH ] in water producing an emulsion with a solids content of 50-55%.
		Polymerization of vinyl acetate with ethylene also can be used to produce solid vinyl acetate/ethylene copolymers with more than 50% vinyl acetate content.
	www.socplas.org /industry/defs.htm (4802 words)

	HighBeam Encyclopedia - free radical (Site not responding. Last check: 2007-11-01)
		The term free is often dropped in referring to free radicals; this could lead to confusion if the term radical were used synonymously with group in organic chemistry, e.g., by calling an alkyl group an alkyl radical when free radical was not intended.
		Free radical scavenging action of the medicinal herb Limonium wrightii from the Okinawa Islands.
		Rheokinetics and the Influence of Shear Rate on the Trommsdorff (Gel) Effect During Free Radical Polymerization.
	www.encyclopedia.com /html/f1/freeradi.asp (431 words)

	Xerox Technology - Stable Free Radical Polymerization - SFRP
		Stable Free Radical Polymerization is a process-oriented technology that facilitates the preparation of linear or branched polymers having narrow molecular weight distributions and reactive end groups on each polymer chain.
		Furthermore nitroxide-based stable free radical polymerization is particularly suited for emulsion or microsuspension polymerization.
		Nitroxidebased stable free radical polymerization is particularly suited for emulsion or microsuspension polymerization.
	www.xeroxtechnology.com /sfrp (490 words)

	International Union of Pure and Applied Chemistry
		Consequently the notion that radical polymerization was a chain reaction comprising initiation, propagation and termination steps developed during the early 1930s, although termination was not thought to be necessary at first, and was assumed to operate through disproportionation when it did become incorporated into the reaction scheme.
		In addition to the straightforward aspects of homogeneous polymerization, systems in which the polymer produced proved to be insoluble in its own monomer, and systems in which the monomer was adsorbed on an added foreign polymer, merited special study.
		However, until the late eighties the prevailing opinion was that free-radical polymerization was a mature technique, unable to afford polymers with well-defined structures, and lacking the ability to yield, e.g., narrow molecular weight distributions and block copolymers.
	www.iupac.org /publications/macro/2002/182_preface.html (938 words)

	Chem 421 - Free Radical Polymerization - Monomers and Propagation (Site not responding. Last check: 2007-11-01)
		Chem 421 - Free Radical Polymerization - Monomers and Propagation
		Monosubstituted and 1,1-disubstituted vinyl gruops present a choice to the incoming radical (either an initiator fragment or the propagating chain end).
		Results: a steady-state concentration of radicals is established early in the reaction.
	www.chem.rochester.edu /~chem421/frmono.htm (155 words)

	Expert: Plastic Failure Analysis and Expert Witness Expert
		He is very knowledgeable in the chain transfer chemistry of both free radical and anionic polymerization of vinyl monomers.
		He is a well-known expert on free radical polymerization as well as on living or controlled radical polymerization.
		He was one of the early pioneers in developing an understanding of living radical polymerization and holds several patents on this area of technology.
	www.intota.com /viewbio.asp?bioID=765810&perID=722299 (1276 words)

	Handbook of Radical Polymerization
		Handbook of Radical Polymerization provides a concise yet comprehensive source of information on mechanisms, synthetic techniques, and characterization methods and addresses future trends for polymers made by free radical intermediates.
		Conventional radical polymerization (RP) and living radical polymerization (LRP) mechanisms receive extensive coverage together with all the other important methods of controlling aspects of radical polymerization.
		To provide comprehensive coverage we have included chapters on fundamental aspects of radical reactivity and radical methods in oraganic synthesis, as these are highly relevant to the chemistry and physics underpinning recent developments in our understanding and exploitation of conventional and living free radical polymerization methods...”
	www.polysurfacesbookstore.com /pages/3710.html (209 words)

	IBM Research \| Almaden Research Center \| Science and Technology \| Polymer Science \| Living free radical polymerizations (Site not responding. Last check: 2007-11-01)
		A major component of these systems are polymeric materials, which perform active functions or are critical in the manufacture of these devices.
		In preparation, and to further this progress, our scientists are developing a wide range of techniques based on living polymerization methods, and in particular living free radical procedures to control and probe the effect of structure on the performance of these materials.
		Living free radical polymerization is a recently developed technique for the controlled polymerization of vinyl monomers; this field has witnessed rapid growth in recent years.
	www.almaden.ibm.com /st/chemistry/ps/living (250 words)

	Free Radical Polymerisation: Theoretical Evaluation
		For the case of a (pseudostationary) laser-pulse initiated polymerization process a closed solution could be derived for the pseudostationary radical concentration and for the chain-length distribution of dead polymer terminated by disproportionation or stabilized by chain-transfer to monomer or solvent.
		Recently a method was established that allows the treatment of (pseudostationary) radical polymerization regarding statistical fluctuations of the propagation process.
		Applying this new methode to stationary polymerization processes it turned out that the (established) method of deriving chain-length distributions from propagation probabilities is not fully consistent with the Poissonian character of chain propagation if termination is chain-length dependent [7]: the fluctuation of chain propagation leads to somewhat lower radical concentrations (rates of propagation).
	www.univie.ac.at /mmphc/pp_num.html (3744 words)

	Free Radical Polymerization (Site not responding. Last check: 2007-11-01)
		Many previous ESR polymerization studies have been relatively uncontrolled; the objective here is to develop very well characterized experimental approaches which are motivated by a coherent theoretical picture.
		Initial ESR measurements of polymerizing systems have produced signals which are sufficiently strong to demonstrate the feasibility of the method.
		The project successfully submitted a proposal with the Polymer Research Center to the NSF entitled "An Integrated Theoretical and Experimental Investigation of Free Radical Polymerization." The project was awarded $260,000 for the time period of July 1997 to June 2000.
	www.columbia.edu /cu/ord/FY97/School-InstituteInvestments/SEAS/SIISEASFRP.html (428 words)

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