Methyl methacrylate, dimerization

Polymerizable surfactants capable of working as transfer agents include thiosulfonates, thioalkoxylates and methyl methacrylate dimer/trimer surfactants. Thioalkoxylates with 17-90 ethylene oxide units were produced from ethoxylated 11 bromo-undecanol by replacing the bromine with a thiol group via the thiazonium salt route [8]. In the presence of water-soluble azo initiator the thio ended Transurfs (used at a concentration above the CMC) gave monodispersed latex particles in emulsion polymerization of styrene. However, the incorporation of the Transurf remained low, irrespective of the process used for the polymerization (batch, semibatch, seeded). The stability of the lattices when the surfactant and the transfer function were incorporated in the same molecule was better than when they were decoupled. 

Monteiro et al. have used a RATF Transurf in the ab initio emulsion polymerization of methyl methacrylate at 70° C. The Transurf was synthesized by esterifying a methyl methacrylate dimer with 1,10 decandiol followed by sulfonation. The authors found that only a small amount of Transurf was incorporated and suggested that, in order to increase the Transurf incorporation, the ratio of monomer to Transurf should be kept as low as possible, as achieved, e.g. in starved-feed conditions [12]. 

H NMR spectra were recorded on Briiker ACP 400 or DPX 400 spectrometers using deuterated solvents obtained from CEA or Aldrich. Polymerization kinetics, followed by NMR, were recorded using the Briiker built-in kinetics software. Molecular mass analyses were carried out by gel permeation (size exclusion) chromatography on a Polymer Laboratories system. THF was the eluent at 1.0 mL min with a PL-gel 5 jim (50 X 7.5 mm) guard column, two PL-gel 5 pm (300 x 7.5 mm) mixed-C columns with a refractive index detector. Samples were compared against narrow standards of poly(methyl methacrylate), A/p = 200 to 1.577 x 10 g mol , obtained from Polymer Laboratories, except for methyl methacrylate dimer, trimer, and tetramer which were prepared by catalytic chain transfer polymerization at the University of Warwick. 

An example of this has been reported for reactions of certain quinodimethanes.9 On its own, this reactive species dimerizes. The substance shown actually yields several dimers, but only the major one is shown in Eq. (3-82). When a dienophile like methyl methacrylate is present, a competing reaction, Eq. (3-81), occurs, where again one of several isomeric products is shown. 

The dimeric metallo-ester slowly disproportionates in the absence of monomer forming methyl methacrylate (the monomer, M) and the monomeric metallo-ester, the reverse reaction by which the dimer could be formed from the monomeric metallo-... 

Additional data were obtained from the study of kinetics of the slow disproportionation of the living dimers of methyl methacrylate. The progress of this reaction is shown in Fig. 8 which displays also the respective rates and equilibrium constants. 

Palladium(II) acetate was found to be a good catalyst for such cyclopropanations with ethyl diazoacetate (Scheme 19) by analogy with the same transformation using diazomethane (see Sect. 2.1). The best yields were obtained with monosubstituted alkenes such as acrylic esters and methyl vinyl ketone (64-85 %), whereas they dropped to 10-30% for a,p-unsaturated carbonyl compounds bearing alkyl groups in a- or p-position such as ethyl crotonate, isophorone and methyl methacrylate 141). In none of these reactions was formation of carbene dimers observed. 7>ms-benzalaceto-phenone was cyclopropanated stereospecifically in about 50% yield PdCl2 and palladium(II) acetylacetonate were less efficient catalysts 34 >. Diazoketones may be used instead of diazoesters, as the cyclopropanation of acrylonitrile by diazoacenaph-thenone/Pd(OAc)2 (75 % yield) shows142). 

A range of rare earth metal complexes were subsequently shown to catalyze ethylene polymerization and, on occasion, living characteristics have been reported.226-228 Dimeric hydrides such as (79)—(82) are extremely active with turnover numbers > 1800 s-1 recorded for (79) at room temperature. The samarium hydride (82) also effects the block copolymerization of methyl methacrylate (MMA) and ethylene 229 further discussion may be found in Section 9.1.4.4. 

Several catalyst systems have been described for the tail-to-tail dimerization of methyl acrylate.7 -7 Advantages of the dimerization procedure described here are its mild conditions, efficient use of the catalyst, and high selectivity for the b isomer. Tetrakis(aceto-nitnle)palladium tetrafluoroborate, Pd (NCMe)4(BF )2, also efficiently catalyzes dimerization of ethyl acrylate and methyl methacrylate. The presence of lithium tetrafluoroborate in the reaction mixture increases the rate of the reaction and prolongs catalyst life. Dimerization of methyl acrylate can be effected without lithium tetrafluoroborate if the reaction is performed in mtromethane. 

The monomer units in I are linked tail to tail and not in the normal head-to-tail manner. Therefore I is not comparable with a normal dimer. In substance II a dimer lies to the right of the tail-to-tail linkage. In the copolymerization of a-methylstyrene with, for example, methyl methacrylate, the addition of one molecule of a-methylstyrene corresponds to substance I,... 

Only a few monomers, other than styrene and related monomers, have been investigated by pulse radiolysis. The studies on methyl methacrylate and related monomers have shown the formation of the associated dimer anion of the... 

Dainton and coworkers (11) investigated the polymerization of various monomers with solutions of potassium in dimethoxyethane. Acrylonitrile gave low irreproducible yields of polymer, whereas methyl methacrylate and acrylamide gave no polymer. Styrene polymerized in a reproducible manner to give "living polystyrene. Their data support an ion-radical mechanism with a slow dimerization of the radicals. A 100% yield of polymer was obtained in < 3 seconds, but the optimum molecular weight was not obtained for > 8—9 seconds. 

The participation of Diels-Alder type intermediates in polymerization was considered by Hill et ah (26) in 1939 as a result of the elucidation of the structures of the butadiene homopolymer and the butadiene-methyl methacrylate copolymer resulting from thermal polymerization in emulsion. The considerable amount of alternating 1,4 and 1,2 structures in the homopolymer and the predominantly 1,4 structure of the butadiene in the copolymer which contained more than 50% alternating units of butadiene and methyl methacrylate led to the proposal that the reaction proceeded through a Diels-Alder dimer complex or activated complex. Chain initiation involved a thermal reaction in which the activated com-... 

We complete this section with a study of the effect of TMEDA on the polymerization of methyl methacrylate lithium enolate in THF262. It was concluded that TMEDA hardly affects the kinetics of the polymerization and therefore the monomer-dimer equilibrium. From these figures, TMEDA does not seem to be a better ligand for lithium ester enolates than THF, in line with previous observations by Collum on other organolithium compounds263. 

Methyl methacrylate may also give rise to initiating radicals [13]. A collision of two monomer molecules leads to the formation of linear dimers, trimers, two cyclobutane derivatives and a diradical [14]... 

Addition of a trifluoromethyl group to the C = C bond of methyl methacrylate (12) followed by dimerization has been observed on electrolysis of a mixture of trifluoroacetic acid and 12 in an acetonitrile/water mixture. The dimerized product 13 is obtained only in 3% yield. 

Phosphorescence studies in isobutylene-methyl methacrylate-1-naphthyl-methyl methacrylate co-polymer provided evidence to show that in very dilute solution the chain collapses into more compact structures, and intramolecular excimer formation in poly-(2-vinylnaphthalene) has been shown to exhibit non-Stokes-Einstein behaviour. Laser photolysis of polymers containing phenanthryl groups, such as poly-(9-vinylphenanthrene), indicates the presence of plural dimer sites having different geometries owing to the stacking effect of phenanthrene chromophores. In poly-(2-naphthyl methacrylate). 

Methyl Methacrylate. Isopropyl iodide (0.03 mole) and methyl methacrylate (0.14 mole) were injected into 100 ml. of 0.30M CoCL solution, and 100 ml. of 1.54M KCN were added with stirring under a nitrogen atmosphere. At the completion of the slow gas evolution, the solution was brown-red. The gas contained 4.72% propane and 27.1% propylene. Separation of an ether extract of the reaction mixture by preparative VPC followed by mass spectral analysis identified the components as unreacted methyl methacrylate, methyl isobutyrate, isopropyl adducts (parent masses 142 and 144) and isopropyl adduct dimers (parent masses 282, 282, and 284). 

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