Studies in Cyciocopolymerization. XIII. A Study of Steric Effects in Cyciocopolymerization of Divinyl Ether with Substituted Electron-Acceptor Alkenes

The equilibrium constants for charge-transfer (CT) complex formation between divinyl ether (DVE) and several sub-stituted maleic anhydrides and 2-cyclopentene-l,4-dione were measured in CHC13 by use of UV spectroscopy. The copolymerizaticn of DVE with these acceptor monoolefins produced regular cyclocopolymers of constant 1:1 or 1:2 (DVE:monoolefin) composition regardless of the feed composition. Comparison of the CT complexation and the cyciocopolymerization leads to the following conclusions: 1) A strong CT complex gives regular cyclocopolymer of constant 1:1 composition having a copolymer backbone made up of only 1,4-diene units: 2) when a monoolefin is un-reactive (often sterically), the 1:1 cyclocopolymer is pro-duced: and 3) if CT complexation is weak and the monoolefin is reactive toward radicals (but not so reactive as to homo-polymerize easily), a 1:2 alternating cyclocopolymer is produced. A facile and quantitative elimination of hydrogen halides with dilute aqueous NaOH solution was found.