Homopolymerization of methyl methacrylate

Figure 2. Homopolymerization of methyl methacrylate in presence of china clay or glass. Key (china clay) X—X, sodium bisulfite freshly prepared O—O,...

Jagodic et al. (1975, 1976) also studied the effect of the HLB of emulsifying agents in the emulsion homopolymerization of methyl methacrylate, ethyl acrylate, and acrylonitrile and in the emulsion copolymerization of methyl methacrylate and ethyl acrylate, methyl methacrylate and... 

For homopolymerizations of methyl methacrylate and of styrene, benchmark value data sets have already been put forward [19,20] and critical data evaluation, by this working party, of kp data for other alkyl methacrylates, functional methacrylates, and alkyl acrylates is underway. Values of for the ethene high-pressure polymerization have not yet been derived from PLP-SEC... 

The kinetics of the homopolymerization of methyl methacrylate in the continuous phase of AOT reverse micelles was studied by Vaskova et al. [35]. Strong turbidity was observed in the course of polymerization, although MMA was highly diluted with toluene (Cmma—6%). The MMA polymerization in AOTsystem was compared to that in pure toluene and to that in toluene in the presence of AOT. Avery low polymerization rate was found with water-soluble ammonium persulfate. This indicates that only a small amount of MMA is present in the AOT water pools and that the APS radicals remain trapped inside. 

Methyl methacrylate-MA copolymerizations and property studies of the copolymers have also received substantial attention.Conditions have been developed for preparing alternating (1 1) copolymers of methyl methacrylate-MA (see Chapter 10). However, typical copolymerization conditions produce random copolymers. Binary mixtures of the monomers have been copolyirier-ized in solution, with peroxide initiators at 60°C and at pressures <4 000 atm. In benzene solvent, the specific viscosity (rjsp) of the copolymers varied from 1.10 to 5.27, as pressure increased from 1 to 4 000 atm. The composition of the copolymers was almost independent of pressure. The rates of copolymerization under these conditions increased from 4.34 to 194.0 %/h. The copolymerization rate constant for the pair, at 25°C, has been estimated as 40 liters morS The rate increase, which results from increasing chain propagation rate constants (Rp) with increasing pressure, was of the same order observed for homopolymerization of methyl methacrylate. 

Two free radical-initiated polymerizations are used in turn as examples the homopolymerization of methyl methaK rylate and the copolymerization of styrene n-butyl methacrylate. 

In this paper the GPC interpretation underlying the kinetic model of methyl methacrylate polymerization previously publMied and by now shown to be useful is detailed and updated. It provides a prime example of the conventional experimental use of GPC in homopolymerization studio. 

In connection with the cause of the field influences on the cationic homopolymerization, it is interesting to study how free radical polymerizations are affected by an electric field. Table 1 shows that both the polymer yield and the degree of polymerization were not affected at all by the field, though the intensity was much higher than that applied to cationic systems. The situation was the same for free radical polymerizations of styrene by benzoylperoxide (72), and of methyl methacrylate by benzoylperoxide and azobisisobutyronitiile (77). 

The copolymerization equation is valid if all propagation steps are irreversible. If reversibility occurs, a more complex equation can be derived. If the equilibrium constants depend on the length of the monomer sequence (penultimate effect), further changes must be introduced into the equations. Where the polymerization is subjected to an equilibrium, a-methylstyrene was chosen as monomer. The polymerization was carried out by radical initiation. With methyl methacrylate as comonomer the equilibrium constants are found to be independent of the sequence length. Between 100° and 150°C the reversibilities of the homopolymerization step of methyl methacrylate and of the alternating steps are taken into account. With acrylonitrile as comonomer the dependence of equilibrium constants on the length of sequence must be considered. 

Sodium bisulfite-china clay proved to be an efficient initiator for homopolymerization and graft polymerization of methyl methacrylate onto cellulose. Grafting reactions using ceric ammonium sulfate, sodium bisulfite-soda lime glass or -china clay are inhibited or retarded on adding soda lignin to the grafting medium. 

Homopolymerization reactions were also carried out with the use of methyl methacrylate monomer. 

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. 

The free radical copolymerization of methyl methacrylate or acrylonitrile in the presence of zinc chloride with allylic compounds such as allyl alcohol, allyl acetate, and allyl chloride or butene isomers such as isobutylene, 1-butene, and 2-butene is characterized by the incorporation of greater amounts of comonomer than is noted in the absence of zinc chloride (35). Analogous to the radical homopolymerization of allylic monomers in the presence of zince chloride, the increase in the electron-accepting capability of the methyl methacrylate or acrylonitrile as a result of complexation results in the formation of a charge transfer complex which undergoes homopolymerization and/or copolymerization with a polar monomer-complexed polar monomer complex. 

Acid Effects in UV Comonomer Grafting of Methyl Methacrylate. The UV grafting of methyl methacrylate dissolved in methanol to cellulose is complicated by the degree to which competing homopolymerization occurs. The problem most often encountered is the solidification... 

Mono-Cp titanium catalyst systems are also suitable for the polymerization of polar and non-polar olefinic monomers. The reduction of a mixture of Cp TiMe3 and Ph3C[B(C6F5)4] with zinc produces a catalyst for the syndiotactic homopolymerization of styrene. The same catalyst mediates the polymerization of methyl methacrylate to poly(methyl methacrylate) (PMMA) with >65% of syndiotacticity. This system is also effective for the co-polymerization of styrene/methyl methacrylate upon optimal conditions. A new polymerization mechanism to explain the characteristics of the polymers is proposed based on sequential conjugate addition steps.541... 

Problem 7.20 Bulk polymerization of methyl methacrylate (MMA) at 60°C with 0.9 g/L of benzoyl peroxide yielded a polymer with a weight average degree of polymerization of 8600 at low conversions. Predict the conversions of MMA at which gelation would be observed if it is copolymerized with 0.05 mol% of ethylene glycol dimethaciylate (EGDMA) at the same temperature and initiator concentration as in the homopolymerization case. 

Zirconocenes and lanthanocenes active for olefin polymerization do, in fact, carry out well-controlled homopolymerizations of (meth)acrylic monomers, but polymerization takes place by an enolate mechanism in which the conjugated carbonyl group plays a crucial role in stabilizing the active center. Both monometallic and bimetallic mechanisms have been documented. Collins and co-workers developed a zirconocene group-transfer polymerization (GTP) technique for the polymerization of methyl methacrylate (MMA) which utilizes a neutral zirconocene enolate as an initiator and the conjugate zirconocene cation as a catalyst (Scheme 3). ... 

Jaisinghani and Ray (40) also predicted the existence of three steady states for the free-radical polymerization of methyl methacrylate under autothermal operation. As their analysis could only locate unstable limit cycles, they concluded that stable oscillations for this system were unlikely. However, they speculated that other monomer-initiator combinations could exhibit more interesting dynamic phenomena. Since at that time there had been no evidence of experimental work for this class of problems, their theoretical analysis provided the foundation for future experimental work aimed at validating the predicted phenomena. Later studies include the investigations of Balaraman et al. (43) for the continuous bulk copolymerization of styrene and acrylonitrile, and Kuchanov et al. (44) who demonstrated the existence of sustained oscillations for bulk copolymerization under non-isothermal conditions. Hamer, Akramov and Ray (45) were first to predict stable limit cycles for non-isothermal solution homopolymerization and copolymerization in a CSTR. Parameter space plots and dynamic simulations were presented for methyl methacrylate and vinyl acetate homopolymerization, as well as for their copolymerization. The copolymerization system exhibited a new bifurcation diagram observed for the first time where three Hopf bifurcations were located, leading to stable and unstable periodic branches over a small parameter range. Schmidt, Clinch and Ray (46) provided the first experimental evidence of multiple steady states for non-isothermal solution polymerization. Their... 

The rates of free radical polymerizations differ significantly from those of the corresponding homopolymerizations (Table 22-14). Addition of a small amount of styrene to methyl methacrylate reduces the overall rate by a factor of 2.5, whereas the same addition of methyl methacrylate to styrene only alters... 

For example, methyl methacrylate block copolymers are much less studied than those of styrene. Anion chain transfer occurs at the pendent ester group, drastically reducing the yield of block copolymers. Poly(methyl methacrylate-b-isoprene) has been prepared, however, by using an ingenious chain cap of l,l -diphenylethyl-ene(27,28). i l diphenylethylene will not anionically homopolymerize, therefore it adds only one mer to the macroanion. This anion is more stable in the presence of methyl methacrylate, but will initiate further polymerization. Other workers have reported the preparation of isoprene-methyl methacrylate block copolymers by sequential addition to "living" polyisoprene anions(29,30),... 

Haddleton, D. M., et al. (1997). Identifying the nature of the active species in the polymerization of methacrylates inhibition of methyl methacrylate homopolymerizations and reactivity ratios for copolymerization of methyl methacrylate/n-butyl methacrylate in classical anionic, alkyUithium/trialkylaluminum-initiated, group transfer polymerization, atom transfer radical polymerization, catalytic chain transfer, and classical free radical polymerization. Macromolecules, 30(14) 3992-3998. 

The conditions used for the synthesis of star polymerization of methyl methacrylate has been extended to lauryl methacrylate (LMA). However, the linear living poly(LMA) chain end did not undergo star pol)mierization with EGDMA. However, when a second dose of catalyst was introduced after the complete homopolymerization of LMA, prior to addition of EGDMA, star formation was found to occur. Poly(LMA) stars with a polydispersity of 1.9 and possessing up to ten arms could be prepared [31]. 

Example 7.5 In an effort to graft gelatin with polymethyl methacrylate (PMMA), 2g of potassium persulfate and 20 g of gelatin are dissolved in water. This is added to 40 g of methyl methacrylate (MMA), and the reaction mass is made up to 500 cm. This recipe does not contain any surfactant and the polymerization at 70°C is found to give stable emulsion polymenzation. Experimental analyses of samples show a copious formation of gelatin grafts, which suppress the homopolymerization of MMA [29]. Explain this phenomenon through a kinetic model. 

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