Polymerization of o-quinodimethanes. III. Polymerization of o-quinodimethanes bearing electron-withdrawing groups formed in situ by thermal ring-opening isomerization of corresponding benzocyclobutenes
✍ Scribed by Keisuke Chino; Toshikazu Takata; Takeshi Endo
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 186 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0887-624X
No coin nor oath required. For personal study only.
✦ Synopsis
The substituent effect on the radical polymerization of o-quinodimethanes, generated by thermal isomerization of benzocyclobutenes, was investigated. Polymerizations of three benzocyclobutenes bearing electron-withdrawing groups were studied, namely 1-cyanobenzocyclobutene (1), 1-chlorobenzocyclobutene (2), and 1-bromobenzocyclobutene (3). While radical polymerizations of 2 and 3 did not afford any polymer, radical polymerization of 1 afforded n-hexane-insoluble polymer(M n ϭ 5000) in moderate yields at temperatures above 120°C. The structure of the obtained polymer was confirmed to be a ring-opened polymer(4) by IR, 1 H-, and 13 C-NMR. The yield of the polymer increased with an increase in the initiator concentration. The polymer yield reported in this paper is higher than those of benzocyclobutenes bearing electrondonating groups, reported previously by the authors. The semi-empirical molecular orbital calculation supported the contribution of ring-opening polymerization of spirocompounds, rejecting the possibility of 1,4-polymerization. Lastly, radical copolymerizations of 1 with various comonomers were also performed to obtain the corresponding copolymers.