Primary Hydroxy-Terminated Polylsobutylene via End-Quenching with a Protected N-(omega-Hydroxyalkyl)pyrrole
Polymers and High Performance Materials
N-(2-tert-Butoxyethyl)pyrrole was used to end-quench TiCl(4)-catalyzed quasiliving isobutylene polymerizations initiated from 2-chloro-2.2.4-trimethylpentane and 5-tert-butyl-1,3-di(2-chloro-2-propyl)benzene at -60 degrees C in 60/40 (v/v) hexane/methyl chloride. End-capping was near-quantitative except for the formation of < 5% exo-olefin chain ends, wtih alkylation occurring in both the C-3 (57%) and C-2 (38%) position on the pyrrole ring. Coupling was not observed for the monofunctional polymers; however, quenching of difunctional polymers resulted in small amounts of coupling due to dialkylation at the pyrrole ring. Ther terminal tert-butyl grou pof the N-(2-tert-butoxyethyl)pyrrole-capped polyisobutylene was rapidly and quantitatively removed in situ by addition of ethylaluminum dichloride and sulfuric acid to the reaction mixture. Furthermore, heating the reaction mixture to reflux (69 degrees C) forced alkylation by the residual exo-olefin chain ends and induced isomerization of the pyrrole-capped chain ends to yield exclusively [3-polyisobutyl-N-(2-hydroxyethyl)]pyrrole. The primary hydroxy-terminated polyisobutylenes showed excellent, unimpeded reactivity with carboxylic acid and isocyanates typically used in block copolymer synthesis.
Morgan, D. L.,
Storey, R. F.
(2010). Primary Hydroxy-Terminated Polylsobutylene via End-Quenching with a Protected N-(omega-Hydroxyalkyl)pyrrole. Macromolecules, 43(3), 1329-1340.
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