Free-radical polymerization initiation

Poly (methyl Acrylate). The monomer used for preparing poly(methyl acrylate) is produced by the oxidation of propylene. The resin is made by free-radical polymerization initiated by peroxide or azo catalysts and has the following formula ... 

A novel cross-linked polystyrene-divinylbenzene copolymer has been produced from suspension polymerization with toluene as a diluent, having an average particle size of 2 to 50 /rm, with an exclusive molecular weight for the polystyrene standard from about 500 to 20,000 in gel-permeation chromatography. A process for preparing the PS-DVB copolymer by suspension polymerization in the presence of at least one free-radical polymerization initiator, such as 2,2 -azo-bis (2,4-dimethylvaleronitrile) with a half-life of about 2 to 60 min at 70°C, has been disclosed (78). 

Vinyl Acetate CH3COOCH=CH2 OH compds, HCN, Halides, Halogens, Mer-cap tans, Amine, Silanes Oxygen Vap in Air 2.6 to 13.4% > Ambient > Ambient Inhibitor—Methyl Ether of Hydroquinone or 3-5ppm Diphenylamine. Store in a dry, cool place shield from light impurities 20.9-21.5 402 427 Free-radical polymerization initiated by Benzoyl Peroxide... 

From these experimental and modeling studies, the mechanism of the living free radical polymerizations initiated by a combination of TED and DMPA have been elucidated. The TED produces DTC radicals that preferentially cross-terminate with the propagating carbon radicals. By this cross-termination reaction, the carbon radical concentration is kept low (as was shown in figure 6) and the rate of polymerization is decreased, as is the autoacceleration effect. This suppression of the autoacceleration peak in HEM A polymerizations and, interestingly, in DEGDMA polymerization has been observed to increase as the TED concentrations are increased. This behavior has been predicted successfully by the model as well. 

In the comparison of organic peroxides as free-radical polymerization initiators, one of the measures used is the temperature (T) required for the half-life (tm) to be 10 h. If it is desired to have a lower T, would ty2 be greater or smaller than 10 h Explain briefly. 

Initiators. Free radical polymerization initiated by azoisobutyronitrile, benzoyl peroxide, or di-tert-butyl peroxide may be explosive.4... 

Figure 6.36. Schematic of the formation of gold nanoparticles coated with free-radical polymerization initiators that subsequently yield Au polymer nanostructures through a surface-controlled living polymerization process. Reproduced with permission from Ohno, K. Koh, K.-M. Tsujii, Y Fukuda, T. Macromolecules 2002, 35, 8989. Copyright 2002 American Chemical Society.

Unlike ordinary chain reactions, chain-growth polymerization need not involve free radicals. The reactive center may instead be a carbanion or carbocation generated by intermolecular transfer of a proton or electron. Depending on the sign of the ionic charge on the chain carriers, the overall reaction is called anionic or cationic polymerization. As in free-radical polymerization, initiation is required. 

Since the 1960 s many researchers have been concerned with the development of feasible and industrially useful methods for the synthesis of cellulose graft copolymers3, 4. Recent investigations have shown that the most efficient approach to this problem involves free radical polymerization initiated by redox systems5. An impressive example is the industrial production of mtilon (cellulose-polyacrylonitrile graft copolymer) and other fibers, particularly those with ion-exchange and acid-resistant properties6"8. ... 

Polymerization. The monomer (or comonomers) and polymerization solvents were passed through a column packed with neutral-grade alumina to remove the inhibitor and other impurities. The monomer(s) and a solvent were degassed by several freeze-thaw cycles by using a vacuum line and were distilled at room temperature into an ampoule containing a known amount of AIBN (azobisisobutyroni-trile), a free-radical-polymerization initiator. After additional degassing, the ampoule was sealed, wrapped in aluminum foil, and placed in a thermostatically controlled bath. Several examples of reaction conditions are given in Table I. 

Use Chemical intermediate for free-radical polymerization initiators, organic synthesis. 

Consider a free radical polymerization initiated by 10" M AIBN. At 70°C, ki is 4.0x10 s and f is close to 0.6. If an inhibitor is to be used to suppress polymerization for an hour, what should be its concentration, if every inhibitor molecule accounts for one primary or monomer-ended radical ... 

Most functional monomers and cross-linkers contain one or more vinyl functionalities. Polymerization of this type of compound for the preparation of MIPs is traditionally performed as a free-radical polymerization, initiated via either ther-molytic or photolytic homolysis of an initiator. One of the most commonly used free radical initiators for this purpose is 2,2 -azobis (isobutyronitrile) (AIBN). Other examples of free-radical polymerization initiators are phenyl-azo-triphenyl-methane, tert-butyl peroxide (TBP), acetyl peroxide, benzoyl peroxide (BPO), lauroyl peroxide, tert-butyl hydroperoxide and tert-butyl perbenzoate. 

An increase in temperatuie would cause an increase m all duec primary steps of free-radical polymerization (initiation, propagation, and termination). By looking at the overall rate law ... 

Beilstein Handbook Reference) AI3-26269 BRN 0506416 Carbonochloride acid, 1-methylethyl ester Carbonochloridic acid, 1-methylethyl ester Chloroformic acid isopropyi ester EiNECS 203-563-2 Formic acid, chloro-, isopropyl ester HSDB 2848 Isopropyl chlorocarbonate Isopropyl chloroformate Isopropyl chloromethanoate Isopropylester kyseliny chlormravenci UN2407. Chemical intermediate for free-radical polymerization initiators, also used in organic synthesis. Liquid bpn 105° soluble in EtzO. BASF Corp. ElfAtochem N. Am. PPG Ind. 

Most early thermoplastics, e.g., PVC or PS, were obtained in the free radical polymerization, initiated either by heat or by sunlight. The first systematic studies of the free radical chemistry commenced 80 years later [Ostromislensky, 1911, 1915, 1916]. Fikentscher empirically determined which one of the 30-or-so monomers liked or disliked to copolymerize with each other. The advantage of latex-blending was also established. The theory of the free radical copolymerization was finally developed in the 1940 s [Alfrey et al, 1952]. 

This technique takes advantage of the fact that nltroso dimers are not free-radical polymerization Initiators but are dissociated to active Inhibiting mononltroso derivatives by UV light at about 280 to 340 nm. These dimers are relatively unaffected by light of longer wavelengths. 

Figure K Structure of polyalkyl acrylates and methacrylates. Polymers were synthesized by free radical polymerization Initiated by exposing alkyl acrylate and methacrylate monomers to high doses ( 10 Mev) of ionizing radiation using a Van de Graff accelerator. Polymers were separated from unreacted monomer by precipitating in methyl alcohol and redissolving in chloroform. Purified polymers were dissolved in chloroform for use in coating glass beads columns and glass cover slips.

Krajnc, M., Poljansek, I., Golob, J. Kinetic modeling of methyl methacrylate free-radical polymerization initiated by tetraphenyl biphosphine. Polymer 42(9), 4153 162 (2001)... 

Three basic steps are involved in free-radical polymerization Initiation, which begins the chain growth propagation, which increases the size of the polymer molecule and termination, which ends the growth of the molecule. 

Chem. Descrip. Etherified acrylated melamine/formaldehyde resin (62-68%) in tripropylene glycol diacrylate Uses Crosslinking agent in radiation-cure applies, such as polyester and epoxy acrylates, unsat. polyesters, aliphatic and aromatic urethane acrylates, and most acrylate monomer diluents imparts hardness and gloss, stain and chem. resist, to coatings, paper coatings Features Cured by free radical polymerization initiated by U V or thermal processing... 

Fig. 20 Flow microreactor system for the free-radical polymerization initialed by AIBN and relative rate of the polymerization in the flow microreactor. M T-shaped micromixer Rl, R2 microtuhe reactors...

Uses Chemical intermediate for free-radical polymerization initiators, organic synthesis Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, Atofina http //www.atofinachemicals.com, BASF http //www.basf.com, PPG Ind. http //www.ppg.com]... 

Bromo-2-fluoro biphenyl intermediate, foam builders Alkenyl succinic anhydride intermediate, food additives Soy acid Stearyl alcohol intermediate, food emulsifiers Caprylic/capric acid Tallow acid intermediate, food supplements (tablet form) Cetyl alcohol intermediate, food wrap Vinylidene chloride monomer intermediate, fragrances p-t-Butyl toluene t-Butyl-m-xylene Citral Cyclopentanone Diethyl toluene diamine Dimethyl hexynediol 1,2-Methylenedioxybenzene 2-Methylpentanal Myrcene n-Propyl bromide intermediate, fragrances cosmetics Acetic anhydride n-Butyraldehyde n-Butyric acid Butyric anhydride 2-Ethylhexoic acid Isobutyric anhydride 2-Methylpropanal Propionic anhydride intermediate, fragrances personal care Butyric anhydride Isobutyric anhydride intermediate, free-radical polymerization initiators... 

Free radical polymerization initiators are compounds with bonds that easily undergo thermal homolytic scission, e.g., hydroperoxides, peroxides, peresters, azo compounds, and strongly sterically hindered ethane derivatives ... 

Chain-growth polymerization is the other important polymerization process besides the step reactions, discussed in Sect. 3.1. The condition for the reaction is given in Fig. 3.23. The mechanism of the reaction involves a small number of active molecules, M. Only these active molecules support further polymerization of the monomers, A. The chemical composition is maintained by a continued chain of the same reactions of AwithM. The illustration of the mechanism refers to a free radical polymerization. Initiation, propagation, and termination are the three stages of the reaction. 

Thus, functionality is not an absolute property of a group, but always has to be considered in relation to the reaction partner. The chemical structure of the resulting macromolecules, moreover, will be decided not only by the functionality of the groups capable of polymerization, but also by the functionality of the molecules. The carbon-carbon double bond in vinyl chloride is bifunctional with respect to free radical polymerization initiators. However, the radicals can also attack already formed polymer, where, for example, a chlorine atom is abstracted with termination of a growing end and formation of a new polymer radical. The new polymer radical can in turn initiate vinyl chloride polymerization again ... 

The conclusion of this study is fliat the kinetics of the free-radical polymerization initiated with highly soluble and mobile photoinitiators are governed primarily by monomer ordering. In contrast, initiator efficiency largely controls the polymerization rate for initiations with builder initiators. These were found to display lower mobility and solubility in liquid crystalline environment. 

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