Radical Cyclopolymerization of Divinyl Acetals—Structure Variation with Polymerization Conditions

Abstract

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.

1-O-Vinyl Glycosides via Tebbe Olefination, Their Use as Chiral Auxiliaries and Monomers

“…These results are consistent with investigations by Ringsdorf et al, who reported that cationic polymerizations of simple vinyl acetals were unsuccessful, and radical homopolymerizations failed or proceeded only sluggishly . On the other hand, some examples of radical polymerizations of vinyl acetals have been reported in the literature . One important factor to consider in this context is the substantial steric demand of the 1- O -vinyl glycoside monomers which may even be comparable to highly sterically hindered dendronized monomers .…”

Complex polymer architectures through free-radical polymerization of multivinyl monomers

“…As per the "5 Å rule [G] ", 90 smaller DVMs with a short intervinyl distance, such as unconjugated 1,5-and 1,6 dienes, are inherently desirable. Following Butler's initial study on FRP of diallyldimethylammonium salts, 87,88 various 1,5-and 1,6 dienes such as (meth)acrylic anhydride, 91 divinyl acetals, 92 o-divinylbenzene 93 and diallylsilanes 94 weresubjected to FRP and the structures obtained were demonstrated to have five-and six-membered rings (Figure 5a) distributed along the C-C chains. The rapid expansion of RDRP techniques in the last two decades have greatly facilitated the synthesis of cyclopolymers with well-defined MW, low dispersity and high chain end functionalities.…”

“…Contemporary experimental strategies to engineer MVMs for cyclopolymerization. Cyclopolymerization can be achieved by either using small DVMs (A) 87,[91][92][93]95,96,179 or by orienting the vinyl moieties close to one another through the use of a bulky template (Ba), [100][101][102][103][104][105][180][181][182][183] a metal template (Bc), [106][107][108] by exploiting hydrogen bonding (Bb) [110][111][112] or by constraining the reacting monomers in nanochannels (C) 115 . Figure 6.…”

Synthesis and 13C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s

“…Other examples of simple vinyl acetals had been reported to be nonpolymerizable, [9] and divinyl acetals had been found to produce complex mixtures of microstructures. [10] It was, hence, not obvious (i) that the polymerization would work regioselectively in the sense of a 1,2-polyaddition, (ii) what kinds of regiochemical defects (head-head, the aglycon with the absolute configuration of the latter. The influence of the stereoconfiguration of β-and γ-C atoms as well as the regiochemistry of the aglycon on the chemical shifts of the α-C and the anomeric C atom was also investigated.…”