Methyl methacrylate reaction with radicals

There are some indications that the situation described above has been realized, at least partially, in the system styrene-methyl methacrylate polymerized by metallic lithium.29 29b It is known51 that in a 50-50 mixture of styrene and methyl methacrylate radical polymerization yields a product of approximately the same composition as the feed. On the other hand, a product containing only a few per cent of styrene is formed in a polymerization proceeding by an anionic mechanism. Since the polymer obtained in the 50-50 mixture of styrene and methyl methacrylate polymerized with metallic lithium had apparently an intermediate composition, it has been suggested that this is a block polymer obtained in a reaction discussed above. Further evidence favoring this mechanism is provided by the fact that under identical conditions only pure poly-methyl methacrylate is formed if the polymerization is initiated by butyl lithium and not by lithium dispersion. This proves that incorporation of styrene is due to a different initiation and not propagation. 

Polymerization of methyl methacrylate monomer with cobalt-60 as source of y-rays, Free radical formation is involved in both cross-linking and polymerization reactions This technique is also being applied in the textile finishing field for grafting and cross-linking fibers with chemical agents for durable-press fabrics. 

A blend containing 10% of PMMA was similarly irradiated at 150 C. The only significant volatile product was methyl methacrylate and the weight loss, corresponding to the amount of the PMMA blended, was complete after 5 hours. Infra-red spectral measurements indicated the complete absence of methacrylate in the residue. At all irradiation times up to 5 hours the methacrylate content of the blend is completely separable from the PP by acetone extraction. Thus, these experiments could provide no positive evidence of reaction of either PMMA radicals or methyl methacrylate monomer with PP radicals, all of which were known to be present in the system. 

Pyrolysis of poly(methyl methacrylate) occurs with a significant proportion of monomer formation. Table 2.1.1. indicates 95% monomer yield, while the results from Table 6.7.20 show only about 59%. The disparity is caused by the differences in the pyrolysis conditions. As shown in Section 2.1, the thermal decomposition of poly(methacrylate esters) is dominated by unzipping, which is a radical propagation reaction with the cleavage of the bond in p-position to the atom bearing the unpaired electron and also p to the double carbonyl bond. This reaction leads to the formation of monomer as shown below (R = CHs for the methyl ester) ... 

In recent years, crosslinkable polymers have found a wide demand in the areas of interpenetrating polymer networks, non-linear optical materials, macro- and microlithography, and the formation of more thermally and chemically resistant materials. With this in mind, the controlled ROMP of 5-methacryloyl-l-cyclooctene (Scheme 8) was investigated to produce a linear polymer with cross-linkable methacrylate side chains. In addition, the copolymerisation of this monomer with cyclooctadiene (Scheme 9) allowed for the incorporation of a varying number of methacrylate side chains on the polymer backbone [23]. These copolymers were crosslinked through the methacrylate side chains with either thermal or photochemical initiation. Reaction of this multifunctionalised methacrylate polymer with methyl methacrylate under free radical polymerisation conditions led to the formation of AB crosslinked systems of poly(methyl methacrylate). A comparison of the... 

The reaaions of the radicals (whether primary, secondary, solvent-derived, etc.) with monomer may not be entirely regio-or chemoselective. Reactions, such as head addition, abstraction, or aromatic substitution, often compete with tail addition. In the sections that follow, the complexities of the initiation process will be illustrated by examining the initiation of polymerization of two commercially important monomers, S and methyl methacrylate (MMA), with each of three commonly used initiators, azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), and di-t-butyl peroxyoxalate (DBPOX). The primary radicals formed from these three initiators are cyanoisopropyl, benzoyloxy, and t-butoxy radicals, respectively (Scheme 7). BPO and DBPOX may also afford phenyl and methyl radicals, respectively, as secondary radicals. 

In a similar way, graft copolymers have been synthesized by reaction of a polyurethane carrying an isocyanate function at the chain end with a poly(methyl methacrylate) backbone with some pendant OH functions, the latter species being obtained by free radical copolymerization of MMA with some hydroxyethyl methacrylate. 

For the free radical polymerization of methyl methacrylate (MMA) with 0.5 wt% 2,2 -azo-bis-isobutyronitrile (AIBN) initiator, the reaction is accelerated in nanopores, as shown in Fig. 11.6, where conversion x versus time is shown for the reaction in the bulk, as well as in native hydrophilic and silanized hydrophobic 13-nm diameter pores of controlled pore glass (CPG) [63,64] experimental results are symbols and the solid lines are the model calculations. The free radical... 

Type AD-G is used in an entirely different sort of formulation. The polymer is designed for graft polymerisation with methyl methacrylate. Typically, equal amounts of AD-G and methyl methacrylate are dissolved together in toluene, and the reaction driven to completion with a free-radical catalyst, such as bensoyl peroxide. The graft polymer is usually mixed with an isocyanate just prior to use. It is not normally compounded with resin. The resulting adhesive has very good adhesion to plasticised vinyl, EVA sponge, thermoplastic mbber, and other difficult to bond substrates, and is of particular importance to the shoe industry (42,43). 

The auto-acceleration effect appears most marked with polymers that are insoluble in their monomers. In these circumstances the radical end becomes entrapped in the polymer and termination reactions become very difficult. It has been suggested that, in thermodynamic terms, methyl methacrylate is a relatively poor solvent for poly(methyl methacrylate) because it causes radicals to coil while in solution. The termination reaction is then determined by the rate at which the radical ends come to the surface of the coil and hence become available for mutual termination. 

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

Kochi (1956a, 1956b) and Dickerman et al. (1958, 1959) studied the kinetics of the Meerwein reaction of arenediazonium salts with acrylonitrile, styrene, and other alkenes, based on initial studies on the Sandmeyer reaction. The reactions were found to be first-order in diazonium ion and in cuprous ion. The relative rates of the addition to four alkenes (acrylonitrile, styrene, methyl acrylate, and methyl methacrylate) vary by a factor of only 1.55 (Dickerman et al., 1959). This result indicates that the aryl radical has a low selectivity. The kinetic data are consistent with the mechanism of Schemes 10-52 to 10-56, 10-58 and 10-59. This mechanism was strongly corroborated by Galli s work on the Sandmeyer reaction more than twenty years later (1981-89). 

Waters61 have measured relative rates of p-toluenesulfonyl radical addition to substituted styrenes, deducing from the value of p + = — 0.50 in the Hammett plot that the sulfonyl radical has an electrophilic character (equation 21). Further indications that sulfonyl radicals are strongly electrophilic have been obtained by Takahara and coworkers62, who measured relative reactivities for the addition reactions of benzenesulfonyl radicals to various vinyl monomers and plotted rate constants versus Hammett s Alfrey-Price s e values these relative rates are spread over a wide range, for example, acrylonitrile (0.006), methyl methacrylate (0.08), styrene (1.00) and a-methylstyrene (3.21). The relative rates for the addition reaction of p-methylstyrene to styrene towards methane- and p-substituted benzenesulfonyl radicals are almost the same in accord with their type structure discussed earlier in this chapter. 

In this short initial communication we wish to describe a general purpose continuous-flow stirred-tank reactor (CSTR) system which incorporates a digital computer for supervisory control purposes and which has been constructed for use with radical and other polymerization processes. The performance of the system has been tested by attempting to control the MWD of the product from free-radically initiated solution polymerizations of methyl methacrylate (MMA) using oscillatory feed-forward control strategies for the reagent feeds. This reaction has been selected for study because of the ease of experimentation which it affords and because the theoretical aspects of the control of MWD in radical polymerizations has attracted much attention in the scientific literature. 

However, other molecules exist which form free radicals of such high stability that they effectively stop the chain process. These molecules are called retarders or inhibitors the difference is one of degree, retarders merely slowing down the polymerisation reaction while inhibitors stop it completely. In practice vinyl monomers such as styrene and methyl methacrylate are stored with a trace of inhibitor in them to prevent any uncontrolled polymerisation before use. Prior to polymerisation these liquids must be freed from this inhibitor, often by aqueous extraction and/or distillation. 

A radical cyclization of a 2-chloroacyl enamine 157 was used to synthesize 2-substituted pyroglutamates 160. Usually, the radical 158 undergoes an initial 5-endo cyclization (path a) and the resulting intermediate 159 attacked electrophiles like methyl acrylate to give the pyroglutamate 160. Unexpectedly, the reaction with methyl methacrylate took another course and a seven-membered... 

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