Radical polymerization of divinyl ether. Carbon‐13 NMR study of the polymer structure

1985

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ABSTRACT:Radical polymerizations of divinyl formal, acetaldehyde divinyl acetal, and acetone divinyl acetal were conducted under a series of conditions, and the microstructures of the cyclopolymers obtained were examined by 1 H NMR and 13 C NMR spectroscopies. The cyclopolymers contained cis-dioxolane units as the major structure along with other minor structures such as the pendant dioxolane unit and trans-dioxoiane unit. The content of the major structure increased with lowering polymerization temperature and increasing monomer concentration. The uncyclized unit and the six-membered dioxane ring were not formed under any condition. The propagation steps included cyclization and isomerization in addition to monomer addition and are discussed on the basis of variation in polymer structure with polymerization conditions. The methyl substitution at the acetal carbon lowers isomerization of the cydized radical. KEY WORDS NMRSpectroscopy I Poly(divinyl formal) Poly(acetaldehyde divinyl acetal) I Poly(acetone divinyl acetal) Cyclopolymerization I Steric Structure I It has been established in the past decade that head-to-head (five-membered ring) cyclopolymers are formed by radical polymerization of non-conjugated dienes such as divinyl ethers/ -4 diallylamines, 5 • 6 allyl esters of unsaturated acids, 7 methacrylic anhydride, 8 and dimethacry !amide. 9 We studied radical cyclopolymerization of the divinyl acetal family-divinyl formal (DVF), acetaldehyde divinyl acetal (CH 3 -DV A), and acetone divinyl acetal (2CH 3 -DV A)-and found the polymers to be comprized of analogous structural units. 10 migration. The connection of the main structure was invariably made of equal amounts of the meso and racemic structures. No uncyclized unit or six-membered (1,3-dioxane) unit or trans-dioxolane units (Ill and IV) could be detected. These structures (I-IV) are illustrated here for DVF. The same conclusions were obtained for CH 3 -DV A and 2CH 3 -DVA.The 13 C NMR spectral data indicated the predominant formation of the cis-dioxolane ring (1), along with the pendent dioxolane unit (II) produced by intramolecular hydrogen More recently, for DVF it was observed that trans-dioxolane rings are produced under other polymerization conditions. 11 We thus examined the influence of polymerization conditions on the polymer structures of CH 3 -DVA and 2CH 3 -DVA and carried out kinetic analyses on the propagation processes of these three monomers.t Contribution No. 753 from Department of Organic Synthesis.

“…These structures (I-IV) are illustrated here for DVF. The same conclusions were obtained for CH 3 -DV A and 2CH 3 -DVA.…”

supporting

confidence: 84%

“…These differences probably arise from differences in the NMR solvents (CDC1 3 ) for the model compounds and mixtures of C 6 D 6 and a-dichlorobenzene for the polymers) and/or from different magnetic environments due to neighboring units of the polymer.…”

Section: IXmentioning

confidence: 99%

Radical Cyclopolymerization of Divinyl Acetals—Structure Variation with Polymerization Conditions

1985

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“…The polymer was recovered by precipitation in methanol, purified by reprecipitation from benzene and methanol, and freeze-dried. The polymers were white powders, soluble in CHC1 3 , CC1 4 10.19%.…”

Section: Polymerizationmentioning

confidence: 99%

“…1 -3 We recently examined the polymer structure by means of 13 C-NMR spectroscopy and concluded that the cyclopolymerization process involved a fivemembered ring intermediate which would either propagate intermolecularly or cyclize to a bicyclic unit, 4 • 5 as shown in Scheme l. Interestingly, the cyclization process was highly stereoselective.…”

mentioning

confidence: 99%

Radical Cyclopolymerization of Divinyl Ethers. The Polymerization Kinetics and the Polymer Structure.

1981

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ABSTRACT:The radical polymerizations of divinyl ether (DVE), cis-propenyl vinyl ether (PVE) and 2-methylpropenyl vinyl ether (CH 3 -PVE) were carried out with AIBN initiator. The polymers were composed of five-membered monocyclic units with pendent unsaturated groups and [3,3,0]bicyclic units. The bicyclization was favored at low monomer concentrations and with methyl-substituted monomers. The microstructures of the polymers were determined by 13 C-NMR spectroscopy, through extensive use of the model compounds. A common cyclopolymerization process has emerged from the data obtained. The monomers react exclusively at the unsubstituted vinyl group, and the trans ring closure produces five-membered monocyclic radicals which then propagate intermolecularly or cyclize to give trans-fused bicyclic units.KEY WORDS 13 C-NMR Spectroscopy I Cyclopolymerization I Poly-(divinyl ether) 1 Poly(cis-propenyl vinyl ether) 1 Poly(2-methylpropenyl vinyl ether)

“…10 • 11 Therefore, we carried out a detailed investigation of the 13 C NMR spectrum ofpoly(divinyl formal) and poly(divinyl acetal)s. The modes of propagation of divinyl formal and divinyl acetals which have been described in the literature are summarized in Schemes I, 2, and 3. These monomers will propagate via the uncyclized (I) and cyclized radicals (Scheme 1).…”

mentioning

confidence: 99%

The Microstructure of Poly(divinyl acetal)s as Determined by 13C NMR Spectroscopy. Ring Stereochemistry and Isomerization Propagation

1979

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ABSTRACT:Divinyl formal, acetaldehyde divinyl acetal, and acetone divinyl acetal were polymerized freeradically, and the polymer structures were determined by detailed analyses of 13 C NMR spectra. The carbon chemical shifts of various structures which might be formed by simple propagation, by cyclopolymerization, and by isomerization propagation were derived from those of a variety of model compounds and their combinations. All the polymers contained the cis-4,5-disubstituted-1 ,3-dioxolane ring as the predominant structural unit in the main chain (ca. 75%) and as the pendent group (ca. 25%). The latter structure was formed by hydrogen abstraction of the propagating methylenedioxolane radical from the neighboring methylene group. Similar hydrogen migration conceivably occurred also during the polymerization of diallylamines.KEY WORDS 13 C NMR Spectroscopy I Poly(divinyl formal) I Poly(divinyl acetal) I Cyclopolymerization I Steric Structure I Divinyl formal and divinyl acetals readily undergo radical cyclopolymerization. 1 -8 These polymers are partially cyclized and the cyclized structure may be composed of five-and/or six-membered rings (see Scheme I)?· 4 In addition, the formation of the isomerized and other structural units was reported in several cases. 5 -7 The polymer structure could be inferred also from the oligomer structure. 9 These structure determinations have been performed by chemical means (hydrolysis and the subsequent determination of the I ,2-glycol content), and by IR and 1 H NMR spectroscopies. However, the conclusions were not necessarily definitive, and the stereochemical information was totally nonexistent.Recently, it was shown that 13 C NMR spectroscopy was a very powerful tool for elucidation of the microstructure of several cyclopolymers. 10 • 11 Therefore, we carried out a detailed investigation of the 13 C NMR spectrum ofpoly(divinyl formal) and poly(divinyl acetal)s.