Methyl dual initiator

In an interesting experiment, Yagci et al. polymerized cyclohexene oxide (CHO) via a photosensitized cationic polymerization with an initiator that contained a TEMPO moiety capable of CRP [281]. Anthracene was reacted with N-ethoxy-2-methyl pyridinium hexafluorophosphate, which produced a radical cation that could then be trapped with TEMPO to create the dual initiating species capable of both cationic and nitroxide-mediated polymerizations (Scheme36). 

Table 12.1 Initiators and monomer used in dual initiator approach to block copolymers. CL caprolactone 4MCL 4-methyl caprolactone MMA methyl methacrylate CMA glycidyl methacrylate FOMA perfluorooctyl methacrylate 10-HA 10-hydroxydecanoic acid.

Dual initiators, i.e., 2-bromo(33 -diethoxypropyl)-2-methylpropiQnate (BrDEP), with two different initiating functions, produce unusual diblocks such as poly(vinyl methyl ether)-b-poly(acrylic acid) as shown. 

Miktoarm stars of the A(BC)2 type, where A is PS, B is poly(f-bulyl acrylate) (PtBA), and C is PMMA [161] have been synthesized, by using the trifunctional initiator 2-phenyl-2-[(2,2,6,6-tetramethyl)-l-piperidinyloxy] ethyl 2,2-bis[methyl(2-bromopropionato)] propionate (NMP, ATRP) (Scheme 86). In the first step, a PS macroinitiator with dual < -bromo functionality was obtained by NMP of styrene in bulk at 125 °C. This precursor was subsequently used as the macroinitiator for the ATRP of ferf-bulyl acry-... 

GLC-FID/FPD and GC-MS Analysis of Oxidation Products. To obtain information regarding the molecular structure of the organic sulfur compounds present in samples, each of the soluble oxidation products were methylated using the diazomethane method and then analysed, initially by both dual FID/FPD gas chromatography, and by GC-MS. Representative FID and FPD traces obtained from the Herrin No. 6 samples are shown in Figures 2 and 3 respectively, while those for the Indiana No.5 samples are shown in Figures 4 and 5 respectively. 

Simple Polar liquid Methyl Chloride and Acetonitrile Acetonitrile shows a bi-exponential decay. The first d y which is characterized with the time constant O.IS pscanbe attributed to the rot-translational relaxation of solvmit molecules in the first solvation sheU. The second decay with the time constant 34.6 ps crxresponds to the structural reorganization beyond the f coordination shell, which brings the solvation structure to the new equilibrium. Thtae has been a emulation study carried out for acetonitrile by Maroncelli. The result exhibits a decay with a dual character a rtqnd initial decay with oscillations, which is characterized by 1 ps decay time. The first quick component h been assigned by the author to the inertisd decay which involves mostly the solvent molecules in the first cot nation shell around the solute molecule. Although the present theory does not reproduce the Gaussian character of the... 

For other substrates, formation of a more stable cationic species drives the [1,2] shift reaction, although thermodynamic partitioning of cationic intermediates and/or subsequent rearrangements can lead to complex product mixtures10. For systems where equilibration of an initially formed cation would be expected to yield mixtures, such as methyl 5-hydroxy-7-trimethylsilyl-bicyclo[2.2.2]octane-2-carboxylates, selective bond migration has been effected by the introduction of a silyl substituent, which serves the dual role of stabilization of the fi carbocation and subsequent elimination to yield an olefinic product14. 

More recently, iodonium salts have been widely used as photoinitiators in the polymerization studies of various monomeric precursors, such as copolymerization of butyl vinyl ether and methyl methacrylate by combination of radical and radical promoted cationic mechanisms [22], thermal and photopolymerization of divinyl ethers [23], photopolymerization of vinyl ether networks using an iodonium initiator [24,25], dual photo- and thermally-initiated cationic polymerization of epoxy monomers [26], preparation and properties of elastomers based on a cycloaliphatic diepoxide and poly(tetrahydrofuran) [27], photoinduced crosslinking of divinyl ethers [28], cationic photopolymerization of l,2-epoxy-6-(9-carbazolyl)-4-oxahexane [29], preparation of interpenetrating polymer network hydrogels based on 2-hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone [30], photopolymerization of unsaturated cyclic ethers [31] and many other works. 

Montei and coworkers [240] reported that Nickel complexes [(X,0)NiR(PPh3)] (X = N or P), designed for the polymerization of ethylene, are effective for home- and copolymerization of butyl acrylate, methyl methacrylate, and styrene. Their role as radical initiators was demonstrated from the calculation of the copolymerization reactivity ratios. It was shown that the efficiency of the radical initiation is improved by the addition of PPhs to the nickel complexes as well as by increasing the temperature. The dual role of nickel complex as radical initiators and catalysts was exploited to succeed in the copolymerization of ethylene with butyl acrylate and methyl methacrylate. 

The addition of Na2C03 serves the dual purpose of stopping the reaction and maximizing the fluorescence of the product, MU, as described above. The initial levels of fluorescence in the extract (at time=0) are often largely contributed by the traces of pre-hydrolyzed substrate (i.e., methyl umbelliferone) in commercial substrate preparations, or coumarins in the extract. It should be pointed out, in fact, that the GUS produced by one transformed plant cell can easily be measured using unpurified commercial MUG and a relatively low-tech fluorimeter (Jefferson et al., unpublished data). To minimize the levels of zero-time fluorescence (the MU in the MUG) the solid stocks of MUG should be kept frozen and dessicated, and the bottle not opened when it is still cold (condensation of water from the air will stimulate hydrolysis in the bottle). The MUG in extraction buffer is fine in the refrigerator for a couple of weeks, but will eventually begin to show increased fluorescence. 

The removal of various heavy metal ions such as Cu ", Co ", Zn ", and from aqueous solutions was conducted [29]. Heavy metal binding with a phosphono-methylated derivative of PEI (PPEI) was initially allowed to occur and then, upon equilibration, PEI was added to initiate precipitation of the PEC together with the heavy metal ion. The PPEI-PEI system was found effective for heavy metal scavenging purposes, even in the presence of high concentrations of non-transition metal ions like Na". The PPEI-PEI PEC was found to be more effective than traditional precipitation methods however, the result was not obtained by the application of premixed complexes, but by a step-by-step addition of PPEI and PEI (similar to other dual systems described here). 

Indeed, it is now possible to extend the range of monomers incorporated into a block copolymer by conducting sequential RAFT and ATRP polymerizations employing a dual functional bromoxanthate iniferter (initiator-transfer agent-terminator). Poly(vinyl acetate)-1 -PS, poly(vinyl acetate)- 7-poly (methyl acrylate), and poly(vinyl acetate)- -PMMA block copolymers with low polydispersity 1.25) were prepared... 

Very recently, Wu and co-workers achieved a novel l2-mediated Radziszewski-type reaction of methyl ketones 8, anilines 9, and tosylmethyl isocyanide (TosMlC) 10 via [2 + 1+1 + 1] annulations for the assembly of 1,2,5-trisubstituted imidazoles 11 (Scheme 7.5) [60]. In this protocol, the methylketones 8 play dual roles as a-dicarbonyl compounds and aldehydes for the first time. Initial studies of the mechanism suggest that the reaction proceeds via a key C-acyfimine intermediate and I2 plays an important role in the self-sorting tandem reaction. 

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