Methacrylic acid polymerization

The furfuryl esters of acrylic and methacrylic acid polymerize via a free-radical mechanism without apparent retardation problems arising from the presence of the furan ring. Early reports on these systems described hard insoluble polymers formed in bulk polymerizations and the cross-linking ability of as little as 2% of furfuryl acrylate in the solution polymerization of methylacrylate121. ... 

Katchalsky, A., and G. Blauer Kinetics of methacrylic acid polymerization... 

Armes et al. have intensively studied the aqueous ATRP of various monomers. Using CuBr/bpy as a catalyst, methacrylic acid polymerization has been shown to be possible in aqueous media at pH values between 6 and 9 [200]. The polymerization occurs very slowly (80% conversion after 21 h at 90 °C, [monomer] [initiator] [catalyst] = 28 1 1) yielding polymers with low molecular weight (M = 2.9xl0 g mol ) and a polydispersity of Mw/Mn = 1.3. This is probably due to a loss of catalytic species occurring from the competitive coordination of carboxylic acids to the copper centers, as mentioned for the case of acrylic acid. The choice of pH is important at pH <6, protonation of the bipyridyl ligand occurs, resulting in loss of control. The choice of initiator is equally important the polymerization is only controlled when the methoxy-capped macroinitiator 46 is used. 

Methacrylic acid polymerizes readily. The reaction is exothermic. The rate of reaction accelerates on heating, which may resnlt in violent rupture of closed containers. The polymerization may be inhibited with a trace quantity of hydroquinone and hydroquinone monomethyl ether (Aldrich 2006). The acid may be stored safely below its melting point. 

Pojman et al. found an unusual mode of propagation when there are large amounts of bubbles 45), In studying fronts of methacrylic acid polymerization, they observed convection that periodically occurred under the front at the same time as the front deformed and undulated. The period of convection was about 20 seconds and remained constant during the entire front propagation. 

The acid chlorides of both acrylic and methacrylic acids polymerize by free-radical mechanism in dry aromatic and aliphatic solvents. Molecular weights of the products, however, are low, usually under 10,000 [273, 274]. Polyacrylic and polymethacrylic acids are used industrially as thickeners in cosmetics, as flocculating agents, and when copolymerized with divinyl benzene in ion-exchange resins. 

Propagation Kinetics of Free-Radical Methacrylic Acid Polymerization in Aqueous Solution. The Effect of Concentration and Degree of Ionization... 

Balcon, B.J., Carpenter, T.A., Hall, L.D. Methacrylic acid polymerization. Traveling waves observed by nuelear magnetic resonance imaging. Macromolecules 25, 6818 (1992)... 

Figure 11.9 A descending front of methacrylic acid polymerization (with benzoyl peroxide initiator). Descending fingers of polymerizing material occur under some conditions.

Balcom, B. J. Carpenter, T. A. Hall, L. D. 1992. Methacrylic Acid Polymerization. Travelling Waves Observed by Nuclear Magnetic Resonance Imaging, Macromolecules 25, 6818-6823. 

Fig. 2. Phase diagram for the polyelectrolyhe complex formed by poly(Af-ethyl-4-vinyl-pyridinium bromide) (polymerization degree 530) and poly(methacrylic acid) (polymerization degree 1830). The dots (represent pH values at which the turbidity of the polymer solutions was first observed at 470 nm. Ionic strength was 0.01 M NaCl (a), 0.1 M NaCl (b), 0.25 M NaCl (c), and 0.5 M NaCl (d). Dashed area represents pH/composition range where the complex is insoluble. Reproduced from Ref 11 with permission.

In this mode of propagation, which was first found in combustion [8], one or more high-temperature spots are observed to move in a helical fashion along the surface of the cylindrical sample. In FP the spinning mode was found in two cases, namely, in (i) anionic activated polymerization of e-caprolactam [9] and (ii) methacrylic acid polymerization [10]. We describe briefly the experimental conditions and observations in both cases. 

Other solvents and initiators are, for example, butanone [495] or ethyl methyl ketone [470,476] with AIBN [496-499] and dioxane with benzoyl peroxide [474,484,500,503]. In benzene as solvent the resulting polymer forms a slurry [504]. AIBN can be used as an initiator in aqueous solutions by solubilizing the initiator with 4% ethanol [504]. Methacrylic acid polymerizes in nitric acid at 5 to 30 °C to a molar mass of 2 x 10 and the product precipitates in acetone as a white powder [505]. Nitrogen dioxide reacts as an initiator in benzene to synthesize poly(acrylic acid) at 50 °C with molar masses of 48,000 [506]. Sodium bisulfite initiates polymerization of methacrylic acid in an aqueous medium but is ineffective for acrylic acid [507]. 

Table 11 Redox systems for the pol5mierization of acrylic and methacrylic acid polymerization.

Figure 8 Spatial temperature profiles for methacrylic acid polymerization fronts 2% w/v of benzoyl peroxide (BPO), 12.5% v/v of fert-butyl peroxide (fBPO). Adapted from Pojman, J. A. Ilyashenko, V. M. ...

An important issue for using FP for polymer synthesis is conversion. We will consider in Section 4.38.5.26 the advantages of FP, some of which will be rapid conversion without the use of solvent. However, if conversion is low and the product must be purified, those advantages will be nonexistent. Initiator burn ouf occurs when the all the initiator has decomposed before the monomer has been completely reacted. For methacrylic acid polymerization with benzoyl peroxide as the initiator, conversion ranged from 80% to below 70% in a 2.2-cm tube (Figures 21 and 22). The conversion was higher in a 1.5-cm diameter tube (85-80%) because the front... 

Figure 4. The temperature profiles of methacrylic acid polymerization fronts with BPO alone, with benzoyl peroxide and t-butyl peroxide (tBPO) and with t-butyl peroxide alone. [BPO] = [tBPO] = 0.0825 mol/kg. Reactions were performed in 1.5 cm (i.d.) tubes. The temperatures indicated correspond to the maximum temperatures reached for each initiator. While the temperature at the monomer/polymer interface was not directly measured, it is believed to be ca. 100 "C...

Figure 15. Descending fingers from a front of poly(methacrylic acid) polymerization.

Noble BB, Coote ML. Effects of ionization on tacticity and propagation kinetics in methacrylic acid polymerization. In Matyjaszewski K, Sumerlin BS, Tsarevsky NV, Chiefari J, eds. Controlled Radical Polymerization Mechanisms. Washington, DC American Chemical Society 2015 51—72. 

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