Bulk polymerization of MMA

Model Description of the Bulk Polymerization of MMA with Chain Transfer to Monomer... 

Various methacrylic-styrene copolymers were prepared in which the reactivity of methacrylate monomers used in the first step decreases in the order MM A > BuMA > benzyl methacrylate. For instance, the bulk polymerization of MMA with such an aromatic azo compound proceeds via a living radical mechanism and the sterically crowded C-C(C6H5)3 terminal bond of polymethacrylate 37 can be cleaved thermally to produce a,co-diaromatic PMMA-h-PS block copolymers in 48-72% yield. 

Table 2. Bulk Polymerization of MMA (8 M) (100 or 200 equiv to [CP-I]o) with CP-I, Conventional Radical Initiator (I), and Catalyst (80 "C)...

Fig.1. Time-conversion (a) and time-molecular weight (b) relationships for bulk polymerization of MMA with 6 at 60-100 °C. [6] = 1.0 x 10 mol/L.

Figure 3.2 Typical variation of with conversion for bulk polymerization of MMA, butyl acrylate (BA) and dodecyi acrylate (DA). The different regions of diffusion control are discussed in the text. (B lsed upon data from reference 10.)...

Fig. 21.13. Conversion development of an ultrasound-induced bulk polymerization of MMA at 298 and 313 K [150]. The broken lines indicate the initial reaction rate.

Complete conversion of acrylates (e.g., butyl) and methacrylates (e.g., methyl) to polymer at 50 °C or 60 °C over a few hours may be obtained in emulsion systems [32,36-38]. In the bulk polymerization of MMA, complete conversion can be achieved after more than 10 days (at 80 °C) [39]. The halting of bulk polymerization at high conversions cannot be ascribed to the drastic decrease in the value of kp, while the polymerization in particles in a high conversion regime (monomer droplets are depleted) proceeds under the same viscosity conditions. The radicals and/or reaction loci. Russell et al. [32] propose that this experimental phenomenon is due to a large decrease in the initiator efficiency, f This conclusion results from the fact that in emulsion systems initiation occurs in the aqueous phase (the viscosity of the continuous phase is low and, therefore, does not change with conversion), whereas in bulk systems initiation takes place in the monomer/polymer phase, which becomes very viscous at high conversions. 

Figure 4 Conversion versus time data for the bulk polymerization of MMA with 0.5wt.% AIBN at 70°C. The dotted line is calculated using eqn [42]. ...

The conversion dependenee of termination was experimentally investigated in detail via the single-pulse pulsed-laser polymerization coupled with online time-resolved near infrared spectroscopy (SP-PLP-NIR) technique. " " This method provides access to chain-length-averaged termination rate coefficients, (kt). The variation of kt) towards increasing monomer-to-polymer conversion, X, is exemplified in Figure 1.5 for bulk polymerization of MMA. 

Figure 5.7 Bulk polymerization of MMA at 22.5°C with AZDN. The rate of initiation is 8.36 X 10 mol/Lsec. (From Ref. 23, with the permission of ACS, Washington)...

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