Ring opening during the cationic polymerization of 2-methylene-1,3-dioxepane: Cyclic ketene acetal initiation with sulfuric acid supported on carbon
✍ Scribed by Peter C. Zhu; Zhihong Wu; Charles U. Pittman Jr.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 740 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-624X
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✦ Synopsis
The stable cyclic ketene acetal, 2-metbylene-1,3-dioxepane, 7, has been polymerized cat ionically in pentane, CHzClj and THF at 25°C to form a polymer which is composed of both ring-opened (40-50% ) and ring-retained (50-60%) structures. Init iatiorr was catalyzed by using H2S0, -supported on activated carbon black. This unique outcome differs significantly from the cationic polymerization of several other five-and six-membered ring cyclic ketene acetals which gave 100% 1,2-vinylpolymerization under these conditions. As the polymerization temperature increased in cationic polymerization of 7 the ring-opened content increased and tbe molecular weight of the polymers decreased in such solvents as cyclohexane, 1,2-dichloroethane, dimethoxyethane, and bis-(2-methoxyet hyl ) ether. The mechanism of this polymerization is discussed. This research also illustrated the ability to initiate the cationic polymerization of cyclic ketene acetals by acidified carbon black while avoiding subsequent polymer decomposition. ICI 1997 ,John Wiley & %ns, Inc. Keywords:
2-methylene-1,3 -dioxepane q cyclic ketene acetal q cationic polymerization . activated carbon black . 1,2-polymerization . ring-opening polymerization q ring-retained polymerization . initiator . catalyst q heterogeneous catalysis