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Topic: Radical initiator

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Free radical

Azo compound

Bond dissociation energy

Polymerization

Peroxide

Condensation reaction

Nucleophilic addition

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	Stable free radical polymerization process and thermoplastic materials produced therefrom - Patent 5449724
		A free radical polymerization process for the preparation of a thermoplastic resin includes heating a mixture comprised of a free radical initiator, a stable free radical agent, and ethylene at a temperature of from about 40.degree.
		The free radical polymerization process is conducted at a pressure of from 1,500 to 5,000 bar and at a temperature of from 40.degree.
		Initiators suitable for use in the present process include, but are not limited to, free radical polymerization initiators, such as peroxide initiators and azo initiators.
	www.freepatentsonline.com /5449724.html (4667 words)

	Free radical addition - Wikipedia, the free encyclopedia
		Free radical addition depends on a reagent having a (relatively) weak bond, allowing it to homolyse to form radicals (often with heat or light).
		As an example a nitrate radical is generated by photolysis of CAN which reacts with an alkyne to generate first a very reactive vinyl radical and then via a 1,5-hydrogen atom transfer (HAT) and 5-exo-trig ring-closure a ketyl radical.
		The ketyl dislodges a nitrite radical which is not reactive enough for propagation and the ketone is formed.
	en.wikipedia.org /wiki/Free_radical_addition (372 words)

	Use of amino or hydrazino peroxides in preparing and curing polymers (US5457162)
		R is a substituted or unsubstituted t-alkyl radical of 4 to 12 carbons, a substituted or unsubstituted t-aralkyl radical of 9 to 13 carbons, a t-cycloalkyl radical of 5 to 12 carbons or a substituted or unsubstituted t-alkynyl radical of 5 to 10 carbons;
		R1 is a substituted or unsubstituted, branched or unbranched, alkyl radical of 1 to 13 carbons, a substituted or unsubstituted cycloalkyl radical of 5 to 10 carbons, a substituted or unsubstituted, branched or unbranched, aralkyl radical of 7 to 11 carbons or a substituted or unsubstituted aryl radical of 6 to 10 carbons;
		R88 is a substituted or unsubstituted alkylene diradical of 2 to 10 carbons, the R88 substituents being alkyl radicals of 1 to 8 carbons, chloro, bromo, carboxy, alkoxy radicals of 1 to 8 carbons, alkoxycarbonyl radicals of 2 to 8 carbons or nitro.
	www.delphion.com /details?pn=US05457162__ (1305 words)

	Non-ionic Chemical Reactions
		For example, the esr signal from methyl radicals, generated by x-radiation of solid methyl iodide at -200º C, is a 1:3:3:1 quartet (predicted by the n + 1 rule).
		Initial formation of a carboxyl radical is followed by loss of carbon dioxide to give a pyramidal bridgehead radical.
		If a radical transfer reagent, such as an alkyl halide or xanthate, is not present in excess, an alkene derived radical may exist long enough to add to other alkene molecules in a repetitive fashion, leading to a polymeric product, as shown here.
	www.cem.msu.edu /~reusch/VirtualText/nonionic.htm (4001 words)

	Free Radical Polymerization Kinetics by Dilatometry
		Radical chain polymerization is a chain reaction consisting of a sequence of three steps: initiation, propagation, and termination.
		Initial meniscus movement is due to two factors: Thermal expansion of the liquid and contraction due to polymerization.
		The overall rate of polymerization should be calculated for all three samples so that the effect of initiator concentration of the rate may be verified (samples 1 and 2) and also the effect of a chain transfer agent on the rate may be investigated (samples 1 and 3).
	www.pslc.ws /macrog/lab/dilat.htm (1530 words)

	U.S. Patent: 5089336 - General purpose siloxane release coatings - February 18, 1992
		Initiators of the anionic polymerization reaction are chosen such that redistribution reactions are much slower than chain growth, thus monofunctional living polymer is produced.
		The copolymerization of the free radically polymerizable monomer and the polymerized siloxane segment to produce the block copolymer useful as a release coating is by step-wise free radical polymerization.
		The free radically polymerizable monomer is dissolved in a suitable inert solvent, if needed, and polymerized by free radical polymerization utilizing the siloxane iniferter compound as a free radical initiator source.
	www.everypatent.com /comp/pat5089336.html (15371 words)

	Vitamin C derivatives as antioxidant agents
		Tocopherols mainly act as a free radical chain breaking antioxidant in liposomes (15) and cellular membranes, but they also possess reactivity as singlet oxygen quenchers and in repairing free radical damages in proteins.
		The curve indicates that as soon as the radical promoter is added, the unsaturated fatty acid is attacked and forms the conjugated diene that absorbs at 234 nm (38,40).
		The radical scavenger momentarily stops the peroxidation of linoleic acid until it is completely consumed as the second plateau indicates, and then the oxidation starts again with the same kinetic as before (38,39).
	www.netsci-journal.com /97v4/97014/vitc5.html (2387 words)

	e-Polymers (Site not responding. Last check: 2007-10-10)
		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)

	Radical initiator - Wikipedia, the free encyclopedia
		Radical initiators are utilized in industrial processes such as polymer synthesis.
		The oxyl radicals are rather unstable and believed to be transformed into relatively stable carbon-centered radicals.
		Radical initiators, especially azo compounds and organic peroxides, are inherently unstable.
	en.wikipedia.org /wiki/Radical_initiator (292 words)

	Matyjaszewski Group - Research - 06- Reducing the Concentration of Catalyst in an ATRP Reaction
		When ATRP was initially developed the concentration of catalyst complex used in a typical polymerization was equivalent to the moles of initiator employed for the reaction i.e.
		Activation occurs readily when the initiator containing a radically transferable atom, most often a halide, diffuses to the immobilized catalyst on the surface of a separable particle, the halide is transferred from the polymer chain end to the immobilized catalyst and initiation of polymerization occurs.
		After deactivating the growing radical the soluble Cu(I) species diffuses to the supported catalyst complex, without a significant diffusion barrier, it is a low molecular weight species, and due to the different redox potential the soluble catalyst is rapidly reconverted to the deactivator, the Cu(II) species, through a halogen exchange reaction with the immobilized catalyst.
	www.chem.cmu.edu /groups/maty/about/research/06.html (4054 words)

	Chem 421 - Free Radical Polymerization - Chain Transfer
		Naturally, there are many even-electron species present in the reaction mixture (i.e., monomer, initiator, solvents, polymer chains, etc.), and all of therse may participate in transfer reactions, depending on the relative reactivities of the structures involved.
		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.
	chem.chem.rochester.edu /~chem421/ct1.htm (604 words)

	High viscosity cyanoacrylate adhesive compositions, and process for their preparation - Patent 4038345
		Significantly higher content of free radical initiators has been inherent in essentially all commercially available polyacrylate thickeners of the type described above, apparently traceable to the fact that the thickeners are prepared by free radical polymerization.
		The free radical initiators generally used in making these thickeners are peroxy initiators, the content of which can be determined easily by well-known analytical methods.
		The polymethylmethacrylate thickener which was used had a reduced viscosity of approximately 8.0 and a free radical initiator content, calculated as benzoyl peroxide, of approximately 0.3% by weight.
	www.freepatentsonline.com /4038345.html (2784 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).
		Initially there are 200 turtles of monomer breed with chain-length set to 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)

	Mechanisms of Carotenoid Antioxidant Behavior
		The author also examined the autoxidation of carotenoids initiated by the radical generator, and found that the autoxidation rate of canthaxanthin and astaxanthin was ~2-fold slower than that of beta-carotene and zeaxanthin.
		Chemical reactions were carried out in homogenous solution, with radicals generated by either of two methods: (1) a modified Fenton reaction, a non-specific oxidative system that generates the hydroxyl radical HO among other oxidants, or (2) by the diazo radical initiator compounds 2,2'-azobis-isobutyronitrile (AIBN) and 2,2'-azobis(2,4'-dimethylvaleronitrile) (AMVN), which undergo unimolecular decomposition to produce peroxyl radicals.
		In the second, cells were incubated continuously from the initial cell seeding in medium containing a fixed amount of astaxanthin (from 0 to 10 nM); 18 hours prior to the end of the experiment, the astaxanthin-containing medium was removed and replaced with medium with or without paraquat.
	www.astaxanthin.org /carot-antiox.htm (7168 words)

	polymer info window
		An example of radical polymerization would be industrial polymerization of ethylene into polyethylene (PET): n C H --------> ~C H~ 2 4 2n 4n A gaseous mixture of ethylene and oxygen (used as a catalyst), is pumped through a mile-long heated pipe.
		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; (iv) Red turtles (radicals) react with each other pairwise.
		B" 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 conidions of atmospheric pressure and room temperature.
	ccl.northwestern.edu /cm/models/polymer/info.html (927 words)

	radical addition
		The peroxide is broken into radicals (initiation) which then abstract an H atom from HBr and generate Br radical (propagation).
		The reaction is initiated by the peroxide molecule breaking into two radicals (homolytic cleavage of the O-O bond).
		These oxygen radicals, which are very unstable, then abstract an H atom from HBr to generate Br radicals (propagation step).
	www.as.ysu.edu /~pnorris/Mechanisms/radadd.html (239 words)

	Air and Water Purifier Conditioner, blog
		The process of claim 9, wherein the initial molar ratio of the Group 2 reagent to the Group 1 reagent (M2/M1) in the Vessel 1 is approximately the inverse of the ratio of the vapor pressures of the Group 2 reagent (VP2) to the Group 1 reagent (VP1), according to the formula: M2/M1=VP1/VP2.
		To increase the dwelling time of the initiator in the reflux condensate, the condensate is continuously pooled (collected) in the second vessel, to which the initiator solution is added, and from which the reaction mixture is continuously or periodically discharged into the main vessel.
		Examples of the free radical initiator include organic and inorganic peroxides such as benzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, t-butyl hydroperoxide, t-butyl peroxyacetate, diisopropylperoxy dicarbonate, 2,2-bis(t-butylperoxy)octan- e, methyl ethyl ketone peroxide, potassium peroxide and hydrogen peroxide; and azo compounds such as.alpha.,.alpha.'-azobisisobutyronitrile.
	thethirdingredient.com (6089 words)

	Course Materials
		As in radical processes, electron flow always occurs from the source of the electrons (tail of the arrow) to the recipient of the electrons (arrow head).
		Radical Addition - The starting material is usually either an alkene or alkyne and a radical initiator is present.
		An initial inspection of the problem yields the following information: it is not a radical reaction due to the absence of initiators; it is not pericyclic due to the absence of a conjugated system.
	www.citadel.edu /chemistry/chem207/orgmat.htm (2295 words)

	Arkema CRP Patent Portfolio
		Polymerization in the presence of a stable free radical and of a free radical initiator
		Polymerization in the presence of a stable free radical and of an iniferter
		Radical polymerization in the presence of several stable free radicals
	www.arkema-inc.com /index.cfm?pag=910 (122 words)

	Polyolefin polymer and method of making same - United States Patent H1,388
		a free radical polymerization initiator comprising a mixture of 2,2'-azobis(2-methyl-butyronitrile) and dicumyl peroxide; and
		Cationic polymerization initiators disclosed include protonic acids, Lewis acids and other cation generators such as alkyl perchlorates and ionizing radiation, and it is further disclosed that the cationic polymerization initiator can be used alone or in conjunction with a cocatalyst.
		The free radical polymerization initiators include any compounds, complexes, or other means (such as ionizing radiation) capable of catalyzing free radical polymerization of any one or more of a variety of monomers, while also being compatible with the metathesis procatalyst and procatalyst activator system.
	xrint.com /patents/us/H1388 (15265 words)

	Whisky – An ESR and Antioxidant Study
		The efficiency of the antioxidant is measured by its ability to quench free radicals and hence slow or stop oxidation of linoleic acid.
		The efficiency is determined according to a standard, that is the generation of free radicals in the absence of an antioxidant.
		In terms of the antioxidant evaluation (Scheme 1), AAPH was utilised as a free radical initiator generating superoxide, and the efficiency was calculated based on the formation of a conjugated diene hydroperoxide generated through the oxidation of linoleic acid in the presence and absence of a free radical scavenger.
	www.aim-digest.com /gateway/pages/general/articles/antiox/whisky.htm (1007 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.
		Photodimers of 9-bromoanthracene are being studied as alkyl halide initiators in atom transfer radical polymerizations (ATRP) leading to anthracene-labeled polymers.
		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)

	Free Radical Initiators
		A photoinitiator is a compound especially aded to a formulation to convert absorbed light energy, UV or visible light, into chemical energy in the form of initiating species, viz, free radicals or cations.
		In a free radical addition polymerization, the choice of polymerization initiator depends mainly on two factors: a) its solubility and b) its decomposition temperature.
		They are typically present in ppm level and the use of a free radical initiator at the polymerization temperature will overwhelm the effect of the stabilizer.
	www.sigmaaldrich.com /Area_of_Interest/Chemistry/Materials_Science/Polymerization_Tools/Free_Radical_Initiators.html (605 words)

	Untitled Document (Site not responding. Last check: 2007-10-10)
		This article helps to explain the mechanism from molecule 42 to 44 in which the tributyltinhydride radical formed by the triethylborane catalyst made an oxygen atom a better leaving group and replaced it with a hydrogen atom.
		In the mechanism for the reduction by the tributyltinhydride-triethylborane system, first the tin radical attacks the bromine to give a radical, then intermediate radical equilibrates, and lastly the tin hydride produces the endo or cis isomer selectively.
		In these series of experiments triethylborane proved to be an effective radical initiator in the presence of a trace amount of oxygen.
	www.umich.edu /~chemh215/W04HTML/SSG4/ssg5/refs.htm (445 words)

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