Radical cyclocopolymerization of divinyl ether and maleic anhydride. A ¹³C‐NMR study of the polymer structure

Abstract

SynopsisThe structure of the 1:2 copolymer of divinyl ether and maleic anhydride was investigated by W-NMR spectroscopy. The polymer contains the bicyclic unit composed of one molecule of each monomer and the maleic anhydride unit. The carbon chemical shift for these units was calculated on the basis of the chemical shift of many model compounds. The major peaks of the cyclopolymer prepared in chloroform were consistent with the presence of the symmetrical bicyclic unit with cis junction and the trans monocyclic anhydride unit. The carbonyl carbon spectrum for the copolymer obtained in a mixed solvent of acetone and CS2 suggested the predominant formation of the unsymmetrical bicyclic unit. The polymerization process was discussed on the basis of these results.

Radical Cyclocopolymerization of Divinyl Ether Derivatives with Maleic Anhydride. The Structure Determination of the Alternating Copolymers by 13C-NMR Spectroscopy

“…Improvements of 1-3 ppm were obtained relative to the previous value. 6 The calculated chemical shifts for the carbonyl carbon and the methine carbon of the trans substituted monocyclic ring, 173.6 and 42.1 ppm, respectively, are in good agreement with the observed values (173.7 and 43.6 ppm) given in Figure 2. The other carbonyl carbon peak at 171.0 ± 0.3 ppm thus belong to the bicyclic ring.…”

“…In fact, the calculated shift for this carbon was 172.9 ppm. 6 It may be concluded that the bicyclic structure is common to the four copolymers. If the bicyclization proceeds in the head-to-tail manner, the 6,5-bicyclic unit (I) will be formed, in stead of the 5,5-bicyclic unit (II) obtainable from the head-to-head bicyclization.…”

“…This possibility was denied for poly(DVE-MAn) prepared in CHC13 . 6 The head-to-tail bicyclization, if it occurs, would give structure VII in the case of poly(PVE-MAn). The limited number of 13 C-NMR peaks observed for this copolymer (in particular, a single peak for the methine carbon adjacent to ether oxygen and only two carbonyl carbon peaks) indicate the formation of highly symmetrical structural units.…”

“…We investigated the structure of the 1 :2 cyclocopolymer by 13 C-NMR spectroscopy and concluded that the polymer was composed predominantly of structure 11. 6 The steric structure of the copolymer could be also determined by a comparison of the observed and calculated chemical shifts.…”

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

“…The predominance of the trans ring closure is observed in the homopolymerization of 1,4-dienes (this study) as well as in their copolymerization. 16 This is in contrast with the cis ring closure observed for monocyclization of I ,6-dienes. 15 · 17 · 18 The five-membered ring is formed in both cases, but the stereochemistry of ring closure is reversed.…”