Homopolymerization Of Methyl Methacrylate Research Articles

Photo‐induced graft copolymerization of methyl methacrylate on cellulose

AbstractGraft copolymerization initiated by ultraviolet light irradiation at 40°C in a hard glass vessel under nitrogen was examined. The graft copolymerization was observed to occur easily after some induction period without any use of photosensitizer, though it was found the per cent grafting and the grafting efficiency were markedly affected by the quantities of cellulose and monomer. In the system without cellulose, homopolymerization of methyl methacrylate hardly took place, but the use of cellulose caused the formation of homopolymer too, and a grafting efficiency in the range of 60–80% generally resulted. Ferric chloride or sodium anthraquinone‐2,7‐disulfonate (AQ) acted on the polymerization reaction as photosensitizers to reduce its induction period. Though ferric chloride acted to develop both the per cent grafting and the number of grafts, not the same effects were observed with AQ. Oxalic acid, which was employed with the object of eliminating very small amount of metals contained in cellulose, was found to act favorably in the formation of grafts, much like ferric chloride.

Line‐intersection method for determining the configurational parameters of cross propagation in copolymerization

AbstractFor the evaluation of the configurational parameters in cross propagation, Σs and Σp for binary vinyl type copolymers whose monomer units both contain an asymmetric carbon atom in the chain, a method is proposed which relies on intersecting straight lines in a Σs versus Σp diagram. We define Σs = σAB + σAB and Σp = σAB·σBA, σ being the probability of forming an isotactic enchainment between the monomer units when B adds to a chain ending in A, or A adds to a chain ending in B, respectively. For these definitions it is assumed that σAB and σBA are not necessarily equal in their numerical values. The method described is applicable to triad probabilities obtained both from copolymers and such homopolymers which have been prepared from copolymers under retention of configuration by a polymer analogous reaction. In this work, triad data have been evaluated which were obtained by NMR from methyl methacrylate‐methacrylic acid copolymers, wherein the methyl methacrylate units were pentadeuterated on the αCH3 and βCH2 groups, as well as from methyl methacrylate homopolymers, the latter being prepared from undeuterated methyl methacrylate‐methacrylic acid copolymers by esterification. The approximate values Σs = 0.38, Σp = 0.02 were obtained for the deuterated copolymers, while Σs = 0.392 ± 0.003 and Σp = 0.037 ± 0.003 were found for the undeuterated homopolymers.

The Radiation-Induced Graft Polymerization of Methyl Methacrylate and Cellulose

The quantitative effects of certain factors on the radiation-induced graft polymerization of methyl methacrylate (MMA) and paper (cellulose) were determined. All irradiations were performed in a medium-intensity gamma radiation field created by neutron activation of 55Mn. Resultant radiation dose rates varied between 1.4 and 3.2 × 105 rads/h, initially, and diminished with a 2.58-h half-life. Sample preparation was an important variable in that paper samples immersed in MMA and irradiated immediately thereafter exhibited no grafting, whereas samples soaked 4 and 24 h prior to irradiation yielded increasing amounts of grafting for the same radiation dose. Hydroquinone, which serves as an ideal inhibitor for bulk MMA, yielded no induction period at all for the MMA-cellulose system. The effects of oxygen on the graft polymerization of MMA were similar to its effects on the homopolymerization of MMA. The use of acetone as a solvent for MMA enhanced the amount of graft polymerization. Even higher yields per absorbed dose were obtained using a water-acetone-MMA solution. Furthermore, no pre-irradiation “soak” was necessary to achieve grafting at relatively low absorbed doses in the MMA-solvent systems.

A tracer study of the hydrolysis of methyl methacrylate and methyl acrylate units in homopolymers and copolymers

AbstractHomopolymers and copolymers were prepared from methyl methacrylate, methyl acrylate, and styrene by radical reactions at 60°C. Monomers suitably labeled with carbon‐14 were used so that it was possible to monitor the hydrolysis of ester groups in the polymers during treatment under alkaline conditions. It was found that methyl acrylate units were hydrolyzed completely whatever their environment in a polymer chain. Under the same conditions only about 9% of the ester groups in a homopolymer of methyl methacrylate reacted; the proportion was increased by the introduction of comonomer units into the polymer chain. For copolymers of methyl methacrylate with methyl acrylate the extent of reaction may be correlated with the lengths of the sequences of methyl methacrylate units.

Mode of termination in the copolymerization of vinyl acetate–isobutyl methacrylate and methyl methacrylate–methyl acrylate at 60°C

AbstractThe mode of termination in the vinyl acetate–isobutyl methacrylate (VA–IBMA) and methyl methacrylate–methyl acrylate (MMA–MA) copolymerization systems has been investigated at 60°C. by using the dye‐interaction technique for functional endgroup estimation. The results show that pairs of poly(vinyl acetate) radicals interact almost exclusively through a disproportionation mechanism. In the homopolymerization of methyl methacrylate and methyl acrylate, about 1.16 and 1.22 carboxyl‐containing endgroups per polymer molecule have been estimated, which shows the predominance of disproportionation over combination in these termination reactions. In poly(isobutyl methacrylate) about 1.55 tagged initiator fragments per chain indicate that 29% of the total radicals terminate through the disproportionation mechanism. Cross termination in the (VA–IBMA) copolymerization system occurs almost entirely through combination for monomer feeds richer in isobutyl methacrylate content while for the MMA–MA system, combination is more important at intermediate monomer feed ratios. These results have been discussed in the light of different explanations for the reaction mechanism.

Extractability of homopolymer of methyl methacrylate from, its graft copolymers with starch

AbstractA study has been made of factors which influence the efficiency of extraction of homopolymer of methyl methyacrylate from its graft copolymers with granular corn starch. The moisture content plays a significant role in the extractability of homopolymer; about 25% moisture seems optimum for many samples, with extractability of homopolymer falling sharply at lower moisture levels. In a series of solvents, the efficiency of removal of ungrafted homopolymer varies in a manner roughly paralleling the relative solvating efficiencies of the various solvents for the homopolymers, as indicated by the reported values of appropriate parameters for polymer solutions. For the starch/PMMA system, chloroform and dichloroethane are about equally efficient, and either is superior to benzene, which in turn is better than toluene, methyl ethyl ketone, or acetone. Soxhlet extraction, though commonly used for graft copolymers, is not as effective for the granular starch/PMMA system as is tumbling the heated mixture of solvent and polymer in a closed container. This is probably due to inefficient percolation of the solvent through the swollen syrupy mass of graft copolymer in the Soxhlet thimble.

An investigation of lead tetraacetate, N‐bromosuccinimide, p‐toluenesulfonyl azide, benzenediazonium fluoborate, and saccharine–dimethylaniline as chain initiators

AbstractThe thermal decomposition of several common materials in equimolar mixtures of styrene and methyl methacrylate has determined the initiator efficiency of the materials and permitted classification of the mechanisms as ionic or free radical. Both lead tetraacetate and p‐toluenesulfonyl azide are such weak catalysts for homolytic polymerization that careful work is required to differentiate catalyzed and blank runs. The proposed catalyst system, saccharine–dimethylaniline, is also homolytic in nature but is even less efficient (1% conversion in 1 hr. at 60°). Benzenediazonium fluoborate is a good initiator but is carbonium ion in nature. The active species is not proved but may be the phenyl carbonium ion. N‐Bromosuccinimide is an inhibitor not only for the monomer mixture but also for the homopolymerization of styrene. It is a catalyst however for the homopolymerization of methyl methacrylate. Apparently styryl free radicals are efficiently scavenged by N‐bromosuccinimide or its fragments to terminate the radical chain. The principal products are probably the brominated materials.