Methyl methacrylate chain transfer polymerization

Fijten MWM, Meier MAR, Hoogenboom R, Schubert US (2004) Automated parallel inves-tigations/optimizations of the reversible addition-fragmentation chain transfer polymerization of methyl methacrylate. J Polym Sci Part A Polym Chem 42 5775-5783... 

If equal concentrations of acrylonitrile and methyl methacrylate were each polymerized at 60°C with equal concentrations of the same initiator, which polymer would have the higher DP and by how much Assume polyacrylonitrile undergoes termination only by radical combination and poly(methyl methacrylate) by disproportionation, that no chain transfer occurs, and that initiator efficiencies are the same in both reactions. (Use Table 4-1 below.)... 

In the photopolymerization of methacrylamide by benzoin methyl ether, chain-transfer to monomer has been found to be important, and benzalde-hyde is reported to be an inefficient photoinitiator of methyl methacrylate polymerization unless benzophenone and triethylamine are present. Acetophenone has been found to sensitize the cycloaddition of maleic anhydride to 7-oxabicyclo[2.2.1]heptan-5-one-2,3-dicarboxylic anhydride, , a-hydroxy-acetophenone derivatives have been found to be non-yellowing initiators, and h.p.l.c. has been used to determine residual carbonyl photoinitiators in u.v.-cured resins. In the emulsion-polymerization of methyl methacrylate using an aromatic ketone and a continuous or intermittent laser, the former conditions were found to be similar to those under continuous u.v. irradiation. The dependence of the polymerization rate and average chain-length on the absorbance of the initiator used in the photoinitiated polymerization of vinyl monomers has been studied. Interestingly, irrespective of all conditions, maximum conversion is observed when initiator absorbance is 2.51. "... 

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. 

Nodono, M. Tokimitsu, T. Tone, S. Makino, T. Yanagase, A. Chain transfer polymerization of methyl methacrylate initiated by organolanthanide complexes. Macromol. Chem. Phys. 2000, 201, 2282-2288. 

Segmented terpolymers of poly(alkyl methacrylate)-g-poly(D-lactide)/poly(dimethylsiloxane) (PLA/PDMS) were prepared by combination of a grafting through technique (macromonomer method) and controlled/living radical polymerization such as atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer polymerization. In a single-step approach, the low molecular weight methacrylate monomer (methyl methacrylate... 

FIGURE 10.2 MALDI TOP mass spectra obtained from the automated spotting of the synthesized poly(methyl methacrylate) polymers at different reaction times. The insert (right top) shows the peak molecular weight (M ) (obtained from MALDI TOFMS spectra) as function of the reaction time. Matrix DCTB. This material is reproduced with permission of John Wiley Sons, Inc. from Fijten MWM, Meier MAR, Hoogenboom R, Schubert US. Automated parallel investigations/optimizations of the reversible addition-fragmentation chain transfer polymerization of methyl methacrylate. J Polym Sci A Polym Chem 2004 42 5775-5783. 

Barner-Kowollik C, Quinn FJ, Nguyen TLU, Heuts JPA, Davis TP. Kinetic investigations of reversible addition fragmentation chain transfer polymerizations cumyl phenyldithioacetate mediated homopolymerizations of styrene and methyl methacrylate. Macromolecules 2001 34 7849-7857. 

Chong YK, Moad G, Rizzardo E, Skidmore MA, Thang SH. Reversible addition fragmentation chain transfer polymerization of methyl methacrylate in the presence of Lewis acids an approach to stereocontroUed hving radical polymerization. Macromolecules. 2007 40 9262-9271. 

Polymerization and Spinning Solvent. Dimethyl sulfoxide is used as a solvent for the polymerization of acrylonitrile and other vinyl monomers, eg, methyl methacrylate and styrene (82,83). The low incidence of transfer from the growing chain to DMSO leads to high molecular weights. Copolymerization reactions of acrylonitrile with other vinyl monomers are also mn in DMSO. Monomer mixtures of acrylonitrile, styrene, vinyUdene chloride, methallylsulfonic acid, styrenesulfonic acid, etc, are polymerized in DMSO—water (84). In some cases, the fibers are spun from the reaction solutions into DMSO—water baths. 

The above explanation of autoacceleration phenomena is supported by the manifold increase in the initial polymerization rate for methyl methacrylate which may be brought about by the addition of poly-(methyl methacrylate) or other polymers to the monomer.It finds further support in the suppression, or virtual elimination, of autoacceleration which has been observed when the molecular weight of the polymer is reduced by incorporating a chain transfer agent (see Sec. 2f), such as butyl mercaptan, with the monomer.Not only are the much shorter radical chains intrinsically more mobile, but the lower molecular weight of the polymer formed results in a viscosity at a given conversion which is lower by as much as several orders of magnitude. Both factors facilitate diffusion of the active centers and, hence, tend to eliminate the autoacceleration. Final and conclusive proof of the correctness of this explanation comes from measurements of the absolute values of individual rate constants (see p. 160), which show that the termination constant does indeed decrease a hundredfold or more in the autoacceleration phase of the polymerization, whereas kp remains constant within experimental error. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Solomon (3, h, 5.) reported that various clays inhibited or retarded free radical reactions such as thermal and peroxide-initiated polymerization of methyl methacrylate and styrene, peroxide-initiated styrene-unsaturated polyester copolymerization, as well as sulfur vulcanization of styrene-butadiene copolymer rubber. The proposed mechanism for inhibition involved deactivation of free radicals by a one-electron transfer to octahedral aluminum sites on the clay, resulting in a conversion of the free radical, i.e. catalyst radical or chain radical, to a cation which is inactive in these radical initiated and/or propagated reactions. 

Simplest of the techniques requiring only monomer and monomer-soluble initiator, and perhaps a chain-transfer agent for molecular weight control. Characterized, on the positive side, by high polymer yield per volume of reaction, easy polymer recovery. Difficulty of removing unreacted monomer and heat control are negative features. Examples of polymers produced by bulk polymerization include poly(methyl methacrylate), polystyrene, and low-density (high pressure) polyethylene. 

Monomer and initiator must be soluble in the liquid and the solvent must have the desired chain-transfer characteristics, boiling point (above the temperature necessary to carry out the polymerization and low enough to allow for ready removal if the polymer is recovered by solvent evaporation). The presence of the solvent assists in heat removal and control (as it also does for suspension and emulsion polymerization systems). Polymer yield per reaction volume is lower than for bulk reactions. Also, solvent recovery and removal (from the polymer) is necessary. Many free radical and ionic polymerizations are carried out utilizing solution polymerization including water-soluble polymers prepared in aqueous solution (namely poly(acrylic acid), polyacrylamide, and poly(A-vinylpyrrolidinone). Polystyrene, poly(methyl methacrylate), poly(vinyl chloride), and polybutadiene are prepared from organic solution polymerizations. 

The low reactivity of a-olefins such as propylene or of 1,1-dialkyl olefins such as isobutylene toward radical polymerization is probably a consequence of degradative chain transfer with the allylic hydrogens. It should be pointed out, however, that other monomers such as methyl methacrylate and methacrylonitrile, which also contain allylic C—H bonds, do not undergo extensive degradative chain transfer. This is due to the lowered reactivity of the propagating radicals in these monomers. The ester and nitrile substituents stabilize the radicals and decrease their reactivity toward transfer. Simultaneously the reactivity of the monomer toward propagation is enhanced. These monomers, unlike the a-olefins and 1,1-dialkyl olefins, yield high polymers in radical polymerizations. 

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