Dioxane polymerization

Others have also looked at the kinetic characteristics of the solution homopolymerization of MA, using benzene, dioxane, and acetic anhydride solvents with BPO initiator. In dioxane, polymerization rates are proportional to initiator concentration to the power, supporting a recombination mechanism for termination of the kinetic chains. Reminiscent of the y-radiation polymerization systems, an increased rate of polymerization and greater molecular weight is observed in acetic anhydride solvent. All evidence supports the assumption that acetic anhydride is not a pure solvent for the... 

In ionic polymerizations termination by combination does not occur, since all of the polymer ions have the same charge. In addition, there are solvents such as dioxane and tetrahydrofuran in which chain transfer reactions are unimportant for anionic polymers. Therefore it is possible for these reactions to continue without transfer or termination until all monomer has reacted. Evidence for this comes from the fact that the polymerization can be reactivated if a second batch of monomer is added after the initial reaction has gone to completion. In this case the molecular weight of the polymer increases, since no new growth centers are initiated. Because of this absence of termination, such polymers are called living polymers. 

Cychc carbonates are prepared in satisfactory quaUty for anionic polymerization by catalyzed transesterification of neopentyl glycol with diaryl carbonates, followed by tempering and depolymerization. Neopentyl carbonate (5,5-dimethyl-1,3-dioxan-2-one) (6) prepared in this manner has high purity (99.5%) and can be anionically polymerized to polycarbonates with mol wt of 35,000 (39). 

Dialkyl peroxides have the stmctural formula R—OO—R/ where R and R are the same or different primary, secondary, or tertiary alkyl, cycloalkyl, and aralkyl hydrocarbon or hetero-substituted hydrocarbon radicals. Organomineral peroxides have the formulas R Q(OOR) and R QOOQR, where at least one of the peroxygens is bonded directly to the organo-substituted metal or metalloid, Q. Dialkyl peroxides include cyclic and bicycflc peroxides where the R and R groups are linked, eg, endoperoxides and derivatives of 1,2-dioxane. Also included are polymeric peroxides, which usually are called poly(alkylene peroxides) or alkylene—oxygen copolymers, and poly(organomineral peroxides) (44), where Q = As or Sb. 

Additional empirical observations concerning this reaction were that use of BF3 as its etherate or addition of small amounts of water (both apparently common practices in certain polymerizations) reduce the overall yield of cyclic products because of chain termination. In a typical reaction mixture, 12-crown-4, 15-crown-5, and 18-crown-6 were formed in 15%, 5% and 4% yields respectively. Dioxane constituted 40% of the product mixture and the remainder was less than 3% each of identified components below the cyclododecamer. ... 

Polymerization of alkynes by Ni" complexes produces a variety of products which depend on conditions and especially on the particular nickel complex used. If, for instance, O-donor ligands such as acetylacetone or salicaldehyde are employed in a solvent such as tetrahydrofuran or dioxan, 4 coordination sites are available and cyclotetramerization occurs to give mainly cyclo-octatetraene (cot). If a less-labile ligand such as PPhj is incorporated, the coordination sites required for tetramerization are not available and cyclic trimerization to benzene predominates (Fig. A). These syntheses are amenable to extensive variation and adaptation. Substituted ring systems can be obtained from the appropriately substituted alkynes while linear polymers can also be produced. 

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

Table 4.6 Extent of Ring-Opening During Polymerizations of 4-Methylene-1,3-dioxolane and 2-Methylene-1,4-dioxane Derivatives...

The approx ratio used is diol, lg/diisocyanate, lg/catalyst, 0.0004g/dioxane, lml. Completion of the polymerization requires 258 hrs at 50°. 

The polymer is then diluted with acet and pptd in w. Post polymerization nitration is accomplished by adding 40Gml of 100% nitric acid at 0° to 25g of the dried polymer. When the polymer is completely dissolved, the excess acid is removed by distn at reduced press. The anhyd dioxane-acet soln is then pptd in methylene chloride and dried. 1... 

Recently, Gallot et al. succeeded in preparing well characterized block copolymers by polymerization of 7-benzyl-L-glutamate NCA and e-carbobenzoxyl-L-lysine NCA with a primary amine ended polystyrene or polybutadiene in dioxane or ben-... 

Five-membered unsubstituted lactone, y-butyrolactone (y-BL), is not polymerized by conventional chemical catalysts. However, oligomer formation from y-BL was observed by using PPL or Pseudomonas sp. lipase as catalyst. Enzymatic polymerization of six-membered lactones, 8-VL and l,4-dioxan-2-one, was reported. 8-VL was polymerized by various lipases of different origins. The molecular weight of the enzymatically obtained polymer was relatively low (less than 2000). 

In polyester synthesis via ring-opening polymerizations, metal catalysts are often used. For medical applications of polyesters, however, there has been concern about harmful effects of the metallic residues. Enzymatic synthesis of a metal-free polyester was demonstrated by the polymerization of l,4-dioxan-2-one using Candida antarctica lipase (lipase CA). Under appropriate reaction conditions, the high molecular weight polymer (molecular weight = 4.1 x 10" ) was obtained. 

Phenol, the simplest and industrially more important phenolic compound, is a multifunctional monomer when considered as a substrate for oxidative polymerizations, and hence conventional polymerization catalysts afford insoluble macromolecular products with non-controlled structure. Phenol was subjected to oxidative polymerization using HRP or soybean peroxidase (SBP) as catalyst in an aqueous-dioxane mixture, yielding a polymer consisting of phenylene and oxyphenylene units (Scheme 19). The polymer showed low solubility it was partly soluble in DMF and dimethyl sulfoxide (DMSO) and insoluble in other common organic solvents. 

Morphology of the enzymatically synthesized phenolic polymers was controlled under the selected reaction conditions. Monodisperse polymer particles in the sub-micron range were produced by HRP-catalyzed dispersion polymerization of phenol in 1,4-dioxane-phosphate buffer (3 2 v/v) using poly(vinyl methyl ether) as stabihzer. °° ° The particle size could be controlled by the stabilizer concentration and solvent composition. Thermal treatment of these particles afforded uniform carbon particles. The particles could be obtained from various phenol monomers such as m-cresol and p-phenylphenol. 

A new crosslinkable polymer was synthesized by the SBP-catalyzed polymerization of cardanol. When HRP was used as catalyst for the cardanol polymerization, the reaction took place in the presence of a redox mediator (phe-nothiazine derivative) to give the polymer. Fe-salen efficiently catalyzed the polymerization of cardanol in organic solvents (Scheme 29). " The polymerization proceeded in 1,4-dioxane to give the soluble polymer with molecular weight of several thousands in good yields. The curing of the polymer took place in the presence of cobalt naphthenate catalyst at room temperature or thermal treatment (150°C for 30 min) to form yellowish transparent films ( artificial urushi ... 

The HRP-catalyzed polymerization of (-l-)-catechin was carried out in an equivolume mixture of 1,4-dioxane and buffer (pH 7) to give the polymer with molecular weight of 3.0 x 10 in 30% yield. Using methanol as co-solvent improved the polymer yield and molecular weight. In the polymerization of... 

Methyl methacrylate Free radical polymerization similar to the above. Also susceptible to rapid anionic polymerizationinduced by RMgX or Na in liquid NHs CH, —CH,—C— 1 COOCH3 Tg 90 Amorphous, even when stretched. Hard. Soluble in aromatic hydrocarbons, esters, dioxane, etc. 

Fig. 10.—Benzoyl peroxide-initiated polymerization of vinyl-i-j3-phenyl-butyrate in dioxane at 60°C plotted as a first-order reaction. [M]o and [M ] represent concentrations of monomer initially and at time t, respectively. In experiments 1, 2, and 3, respectively, [M]o = 2.4, 7.28, and 5.97 g. of monomer per 100 cc. of dioxane. (Results of Marvel, Dec, and Cooke obtained po-larimetrically.)...

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