First studies with methyl methacrylate

One of the first detailed studies on these systems was that of Beaman (26), who showed that methacrylonitrile polymerizes by an anionic chain mechanism when treated with various bases, including Na in liquid ammonia at —75° C. He noted also that low molecular weight polymers are obtained from reaction of acrylonitrile with butylmagnesium bromide. Foster (56) extended the liquid ammonia method to copolymerization studies in which acrylonitrile was combined with styrene, with methyl methacrylate and with vinyl butyl sulfone. Satisfactory data were obtained only with the sulfone, in which case there was some tendency for alternation. 

Very recently, the feasibility of aliphatic tertiary amine like the triethylamine-benzoyl peroxide redox-initiating system in photopolymerization of methyl methacrylate [66] has been reported. In the dilatometric study of methyl methacrylate polymerization at 35°C with various solvents, the initiator exponent was 0.34. The monomer exponent depends on the solvents used. In acetonitrile, pyridine, and bromobenzene, the monomer exponent was 0.5, 0.67, and 1.1, respectively, within the concentration range studied. Benzene and chloroform give first-order dependence of rate on [monomer] and behave as normal (inert) diluents. The activation energy was 3.2 kcal mor. ... 

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). 

A study of the polymerization kinetics of methyl methacrylate, in the presence of PBN, and of molecular-mass properties of the obtained polymers shows that the systems react by the pseudoliving mechanism (699). In the first stages of the polymerization process, PBN reacts with oligomeric radicals, forming stable nitroxyl radical-spin adducts A-, see Scheme 2.207. 

Another important application of NMR to polymer systems is the elucidation of the stereochemical configurations of Polymer chains. Poly (methyl methacrylate) was first studied by Bovey in 1960. It is now possible to analyse for the statistical frequency of occurrence of all possible combinations of up to four successive pairs of units (dyads) capable of occurring with either the same (meso) or opposite (racemic) configurations. 

In a series of papers [216,217], Nakata and Nakagawa have studied the coil-globule transition by static light scattering measurements on poly(methyl methacrylate) in a selective solvent. They have found that the chain expansion factor, a2 = R2/R20, plotted against the reduced temperature, r = 1 - 0/T, first decreases with decreasing r, as it should be, but then begins to increase (see, e.g., Fig. 2 presented in [217]) In the authors opinion, the increase of... 

Few redox studies with cubic mesoporous materials have been reported [52]. The large, complex, three-dimensional pore system offers a unique environment. Ti- and Cr-substituted MCM-48 have been studied for the selective oxidation of methyl methacrylate and styrene to methyl pyruvate and benzaldehyde, respectively, using peroxides as oxidants and were found to outperform TS-1. Ti-MCM-48 has also been found to be better than Ti-MCM-41, TS-1 and Ti02 for the photocatalytic reduction of CO2 and H2O to methane and methanol. Ti-grafted MCM-48 has also been reported as the first functional biomimic of vanadium bromoperoxidase, active at neutral pH and used in the peroxidative halogenation of bulky organic dyes. 

Only one kinetic study exists on initiation of methacrylate polymerization by a sodium compound. The initiator was the disodium oligomer ( tetramer ) of a-methylstyrene and polymerization was investigated at 25°C in toluene in presence of 0.05—0.2 mole fraction of tetrahydrofuran [181]. An internal first order disappearance of monomer was observed, the first order coefficient being directly proportional to active chain and tetrahydrofuran concentrations. The rate coefficients evaluated, e.g. fep = 3.1—13 X 10 1 mole sec at various tetrahydrofuran concentrations, are much lower than those for lithium initiators. They were, however, evaluated using a methyl iodide titration technique to estimate the active chain concentration. In view of the reactivity of tritiated acetic acid with many short chains which are clearly not active in chain propagation, there must be suspicion of similar behaviour with methyl iodide. If this happens, the active chain concentration would be over-estimated and the derived fep value would be too low. Unfortunately no molecular weights of the precipitable polymer were determined, so that it is impossible to check on active chain concentration using this alternative method. 

The first part of this review is dedicated to the polymerization of methyl methacrylate. This is by far the most extensively studied Grignard polymerization system. Some mechanistic and stereochemical aspects of this particular reaction are still controversial, but the results reported by independent research groups are, on the whole, mutually consistent. Other vinyl monomers have been reported to polymerize with the use of organomagnesium compounds. They are regrouped in the subsequent section. The reported results are classified and briefly commented. Studies of many systems led to contradictory results, and no attempt was made to reconcile the resulting divergent interpretations. 

The 1930s saw the introduction of the poly generation and the first of many such thermoplastics was poly(vinyl chloride) or PVC which became commercial reality with the introduction of a plasticiser. At about the same time Du Pont Chemicals also launched the polyamide nylon 66 after studying the network structure of silk. A few years later German researchers developed nylon 6 from caprolactam. In the UK, ICI developed and produced polyethylene, a material vital to the success of radar technology during the Second World War. ICI also made a valuable wartime contribution with the development of poly(methyl methacrylate) or PMMA which was used to make shatterproof and protective screens. 

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