Monomer methyl methacrylate with

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double smface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro quinone to act as a stabiUser or inhibitor of polymerisation. 

Figure 6.3 Log-log plots of Rp versus concentration which verify the order of the kinetics with respect to the constituent varied, (a) Monomer (methyl methacrylate) concentration varied at constant initiator concentration. [Data from T. Sugimura and Y. Minoura, J. Polym. Sci. A-l 2735 (1966).] (b) Initiator concentration varied AIBN in methy methacrylate (o), benzoyl peroxide in styrene ( ), and benzoyl peroxide in methyl methacrylate ( ). (From P. J. Flory, Principles of Polymer Chemistry, copyright 1953 by Cornell University, used with permission.)...

The cross-linking reaction mechanism is also influenced by the presence of other monomers. Methyl methacrylate is often used to improve the uv resistance of styrene-based resins. However, the disparate reaction rates of styrene and methacrylate monomer with the fumarate unsaturation not only preclude the use of more than 8% of the methacrylate monomer due to the significant slowing of the cross-linking reaction but also result in undercured products. 

Polymers containing oxazoline groups are obtained either by grafting the 2-oxazoline onto a suitable existing polymer such as polyethylene or polyphenylene oxide or alternatively by copolymerising a monomer such as styrene or methyl methacrylate with a small quantity (<1%) of a 2-oxazoline. The grafting reaction may be carried out very rapidly (3-5 min) in an extruder at temperatures of about 200°C in the presence of a peroxide such as di-t-butyl peroxide Figure 7.13). 

As with other rigid amorphous thermoplastic polymers such as PVC and polystyrene (see the next chapter) poly(methyl methacrylate) is somewhat brittle and, as with PVC and polystrene, efforts have been made to improve the toughness by molecular modification. Two main approaches have been used, both of which have achieved a measure of success. They are copolymerisation of methyl methacrylate with a second monomer and the blending of poly(methyl methacrylate) with a rubber. The latter approach may also involve some graft copolymerisation. 

We extended the kinetic model to other monomer systems such as styrene and methyl methacrylate. With these, we used common initiators such as benzoyl peroxide and azo-bis-isobutyronitrile. The results of these simulations compared closely with some published experiments. 

Copper bromide and pentakis-A-(heptadecafluoroundecyl)-l,4,7-triazeheptane (1 in Figure 10.9), along with an initiator, ethyl-2-bromoisobutyrate (2 in Figure 10.9), in a perfluoromethylcyclohexane-toluene biphase efficiently catalyse the polymerization of methyl methacrylate, with a conversion of 76 % in 5 h at 90 °C. The resultant polymer has a Mn = 11100 and a molar mass distribution of 1.30. After polymerization, the reaction was cooled to ambient temperature, the organic layer removed and found to contain a copper level of 0.088 % (as opposed to 1.5% if all the catalyst were to have remained in the polymer). A further toluene solution of monomer and 2 could be added,... 

For example isopropylbenzene, which is considered as a model substance for polystyrene, has a chain transfer constant with polymethyl methacrylate radicals equal at 80° C to 1.9 10 4 (30). This means that at equimolecular concentration of monomer (methyl methacrylate) and transfer agent (isopropylbenzene, or in our case polystyrene) only one transfer reaction will occur against five thousand normal monomer addition steps. 

Most dispersion polymerizations in C02, including the monomers methyl methacrylate, styrene, and vinyl acetate, have been summarized elsewhere (Canelas and DeSimone, 1997b Kendall et al., 1999) and will not be covered in this chapter. In a dispersion polymerization, the insoluble polymer is sterically stabilized as colloidal polymer particles by the surfactant that is adsorbed or chemically grafted to the particles. Effective surfactants in the dispersion polymerizations include C02-soluble homopolymers, block and random copolymers, and reactive macromonomers. Polymeric surfactants for C02 have been designed by combining C02-soluble (C02-philic) polymers, such as polydimethylsiloxane (PDMS) or PFOA, with C02-insoluble (C02-phobic) polymers, such as hydrophilic or lipophilic polymers (Betts et al., 1996, 1998 Guan and DeSimone, 1994). Several advances in C02-based dispersion polymerizations will be reviewed in the following section. 

Another real active species was isolated form the reaction of [Cp 2SmH]2 with two equivalents of MMA monomer (methyl methacrylate) [289]. Or-ganolanthanide complexes of type Cp2LnR (R = H, alkyl) are not only effective precatalysts in the polymerization of nonpolar monomers such as ethylene, but also initiate the ideal living polymerization of MMA [289-291]. 

Chemicals. Reagent grade chemicals were used in the study of grafting. Acetone, ethyl alcohol and benzene were redistilled before use. Monomer, methyl methacrylate (MMA), was used fresh after purification and distillation. It was purified following the method adopted by Gupta and Nandy (15). CAS was used after standardization by an usual method (16). All CAS solutions used for the study was acidified with 1% H2SO4. 

The most significant observation in the radical copolymerization of methyl methacrylate with vinylidene chloride in the presence of zinc chloride is the increase in the Q and e values of methyl methacrylate, the increase in the rx value of methyl methacrylate, and the decrease in the r2 value of vinylidene chloride (30). Although it has been proposed that these results arise from the increased reactivity of the complexed methyl methacrylate monomer, a more likely explanation is the homopolymerization of a methyl methacrylate-complexed methyl methacrylate complex accompanied by the copolymerization of methyl methacrylate with vinylidene chloride. 

Mouran et al. [105] polymerized miniemulsions of methyl methacrylate with sodium lauryl sulfate as the surfactant and dodecyl mercaptan (DDM) as the costabilizer. The emulsions were of a droplet size range common to miniemulsions and exhibited long-term stability (of greater than three months). Results indicate that DDM retards Ostwald ripening and allows the production of stable miniemulsions. When these emulsions were initiated, particle formation occurred predominantly via monomer droplet nucleation. The rate of polymerization, monomer droplet size, polymer particle size, molecular weight of the polymer, and the effect of initiator concentration on the number of particles all varied systematically in ways that indicated predominant droplet nucleation. 

New photoreactive polymers with dimethylmaleimide side groups have been prepared, "" and co-polymers of methyl methacrylate with oligourethanes have tensile properties superior to those of the separate homopolymer systems."" New monomers have been prepared for fire-retardant u.v.-curable polymers " and trimethylolpropane has been photopolymerized in the vapour phase. Diphenylsulphoniumbis(methoxycarbonyl)methylide photoinitiates the polymerization of styrene and methyl methacrylate through the formation of... 

Dentin. Preliminary studies have been conducted to determine the feasibility of grafting onto dentin (53). With CAN as initiator, some modification of dentin occurred on treatment with methyl methacrylate. With other monomers, no increase in weight was found. Since dentin is the most highly mineralized collagenous substrate that has been studied, its lack of reactivity towards grafting is expected. 

Hummel et al. (1967) also conducted brief studies of a number of other monomers. Chloroprene behaved simibrly to styrene. Methacrylonitrile behaved somewhat like methyl methacrylate with a definite gel effect. Butyl methacrylate behaved somewhat like styrene but with two small maxima in the rate-conversion curves tbc reasons for this arc unknown but the second small peak could arise from the gel effect. Decyl methacrylate showed only one maximum rate at about 50% conversion. Again the reasons for this behavior are unclear. Isoprene did not polymerize in emulsion at either low or high dose rates. Kaly in et al. (197S) have presented a study of the radiatiorr-induced polymerization of vinyl fiuoride in emulsion. 

Preparation of grafted starches on synthetic polymers. Ce salts are used to oxidize starch and generate free radicals that react with certain monomers (methyl methacrylates, acrylonitrile, vinyl acetate, acrylamide, etc.)... 

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