Methyl methacrylate monomer-copolymer composition

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

Deviations are also observed in some copolymerizations where the copolymer formed is poorly soluble in the reaction medium [Pichot and Pham, 1979 Pichot et al., 1979 Suggate, 1978, 1979]. Under these conditions, altered copolymer compositions are observed if one of the monomers is preferentially adsorbed by the copolymer. Thus for methyl methacrylate (M1 )-/V-vinylcarbazole (M2) copolymerization, r — 1.80, r2 = 0.06 in benzene but r — 0.57, > 2 0.75 in methanol [Ledwith et al., 1979]. The propagating copolymer chains are completely soluble in benzene but are microheterogeneous in methanol. /V-vinylcarba-zole (NVC) is preferentially adsorbed by the copolymer compared to methyl methacrylate. The comonomer composition in the domain of the propagating radical sites (trapped in the precipitating copolymer) is richer in NVC than the comonomer feed composition in the bulk solution. NVC enters the copolymer to a greater extent than expected on the basis of feed composition. Similar results occur in template copolymerization (Sec. 3-10d-2), where two monomers undergo copolymerization in the presence of a polymer. Thus, acrylic acid-2-hydroxyethylmethacrylate copolymerization in the presence of poly(V-vinylpyrrolidone) results in increased incorporation of acrylic acid [Rainaldi et al., 2000]. 

Figure 1. Monomer—copolymer composition relationship for the plasma-initiated copolymerization of methyl methacrylate with styrene. Plasma-initiated polymerization (%) NMR, (x) elemental analysis. Thermal polymerization (O) NMR, (Aj elemental analysis, (—) theoretical curve, tmma = 0.46 =...

Seymour and coworkers (27,28,29,30) actually used these composition gradients to prepare block copolymers by swelling particles containing occluded (i.e., living) macroradicals with a second monomer. Such block copolymers were prepared from occluded vinylacetate, methyl methacrylate, and acrylonitrile macroradicals, and the yield of block copolymers was studied as a function of the solubility and rate of diffusion of the swelling monomer in the particles. 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

In thermal polymerization where the rate of initiation may also vary with composition, an abnormal cross initiation rate may introduce a further contribution to nonadditive behavior. The only system investigated quantitatively is styrene-methyl methacrylate, rates of thermal copolymerization of which were measured by Walling. The rate ratios appearing in Eq. (26) are known for this system from studies on the individual monomers, from copolymer composition studies, and from the copolymerization rate at fixed initiation rate. Hence a single measurement of the thermal copolymerization rate yields a value for Ri. Knowing hm and ki22 from the thermal initiation rates for either monomer alone (Chap. IV), the bimolecular cross initiation rate constant kii2 may be calculated. At 60°C it was found to be 2.8 times that... 

The composition of the copolymers as a function of the composition of the mixture of monomers can be best understood from the practical example of styrene and methyl methacrylate (MMA) as shown in Figure 31. 

Figure 31 Copolymer composition as a function of monomer mixture composition in the case of styrene methyl methacrylate mixtures. Reproduced from Mercier and Marechal [15], Reproduit avec I autorisation de I editeur. Tous droits reserves.

A number of solid acrylic resins, all known under the commercial name of Paraloid, are used in art conservation, dissolved in organic solvents, as consolidants, coatings, or in varnish formulations these resins are generally copolymers formed by two acrylic/ methacrylic monomers [82], Paraloid B-72 is the most widely used acrylic resin in conservation, and is formed by a methyl acrylate/ethyl methacrylate (MA/EMA) copolymer with molar composition 70/30. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

Compositionally uniform copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) are produced in a free running batch process by virtue of the monomer reactivity ratios for this combination of monomers (r (TBTM) = 0.96, r (MMA) = 1.0 at 80°C). Compositional ly homogeneous terpolymers were synthesised by keeping constant the instantaneous ratio of the three monomers in the reactor through the addition of the more reactive monomer (or monomers) at an appropriate rate. This procedure has been used by Guyot et al 6 in the preparation of butadiene-acrylonitrile emulsion copolymers and by Johnson et al (7) in the solution copolymerisation of styrene with methyl acrylate. 

An appropriate formalism for Mark-Houwink-Sakurada (M-H-S) equations for copolymers and higher multispecies polymers has been developed, with specific equations for copolymers and terpolymers created by addition across single double bonds in the respective monomers. These relate intrinsic viscosity to both polymer MW and composition. Experimentally determined intrinsic viscosities were obtained for poly(styrene-acrylonitrile) in three solvents, DMF, THF, and MEK, and for poly(styrene-maleic anhydride-methyl methacrylate) in MEK as a function of MW and composition, where SEC/LALLS was used for MW characterization. Results demonstrate both the validity of the generalized equations for these systems and the limitations of the specific (numerical) expressions in particular solvents. 

Since the late 1960 s a few papers have demonstrated compositional analysis of various polymer systans by Raman spectroscopy. For example, Boerio and Yuann (U) developed a method of analysis for copolymers of glycidyl methacrylate with methyl methacrylate and styrene. Sloane and Bramston-Cook (5) analyzed the terpolymer system poly(methyl methacrylate-co-butadiene-co-styrene). The composition of copolymers of styrene-ethylene dimethacrylate and styrene-divinylbenzene was determined by Stokr et (6). Finally, Water (7) demonstrated that Raman spectroscopy could determine the amount of residual monomer in poly(methyl methacrylate) to the % level. This was subsequently lowered to less than 0.1% (8). In spite of its many advantages, the potential of Raman spectroscopy for the analysis of polymer systems has never been fully exploited. 

Figure 6. Mole percent methyl methacrylate incorporated in poly(methyl)meth-acrylate-co-3-oximino-2-butanone methacrylate) copolymers as a function of monomer feed composition determined by Raman spectroscopy. Key -----------ideality...

Figure 5.4. Kellen-Ttidos plot for calculation of reactivity ratios from composition of monomer mixture, R, and composition of copolymer, E Copolymerization of methacrylic acid with methyl methacrylate in the presence of PEG 20,000. Reprinted from S.PolowinskijEnr.PoZym.t/., 19,679 (1983) with kind permission from Elsevier Science Ltd.

The composition of the grafted side chain copolymer has also been determined by Sakurada (113) and found to be different from the normal copolymer formed with acrylonitrile and butadiene. With styrene the grafted copolymers were found to be richer in acrylonitrile than the normal copolymer. Similar differences were found by Resting (114) with methyl methacrylate and styrene grafted to cotton and by Odian et al. (115) with grafting mixed monomers to Teflon and to polyethylene. It is believed that one monomer may be preferentially sorbed or diffused faster than the other, leading to a different monomer ratio at the actual site of grafting. 

The free radical initiated copolymerization of methyl methacrylate or acrylonitrile with CO has been reported17 . The resulting copolymers contain 14 mol% and 4.5 mol% CO, respectively, and these copolymer compositions were independent of monomer compositions. Interestingly, methyl acrylate could not be copolymerized in the same way. 

A significant decrease in the spread of compositions for copolymer produced by monomer proportionation compared with that produced by bulk charging of monomers can be seen by comparing the optical haze values obtained on a 90-10 methyl methacrylate-a-methylstyrene (MMA-a-MeSt) copolymer system (Table I). 

For compounds bearing acrylate or methacrylate groups, the copolymer compositions were almost the same as the monomer feed compositions, and the molecular weights were nearly identical to that of poly(methyl methacrylate) (PMMA) synthesized as a control under the same reaction conditions. In addition, the dye-bearing repeat units were present uniformly in all molecular weights, as seen by comparing GPC molecular weight distribution curves determined by differential refractometry and by visible absorbance detection at the X of the... 

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