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In Situ Quenching Methods Toward exo ‐Olefin‐Terminated Polyisobutylene
Author(s) -
Ummadisetty Subramanyam,
Morgan David L.,
Stokes Casey D.,
Harrison J.J.,
Campbell Christopher G.,
Storey Robson F.
Publication year - 2013
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201200017
Subject(s) - isobutylene , olefin fiber , chemistry , quenching (fluorescence) , adduct , polymer chemistry , onium , ether , photochemistry , organic chemistry , ion , fluorescence , copolymer , catalysis , polymer , physics , quantum mechanics
exo ‐Olefin‐terminated polyisobutylene was obtained directly from living isobutylene polymerizations by addition of a quenching compound to the living chain ends. Three broad classes of compounds were evaluated including hindered bases such as hindered pyridines and piperidines, N ‐hydro‐2,5‐disubstitutedpyrroles, and sulfides, ethers, and silylethers. The proposed mechanism of quenching unique to each class was discussed, with supporting kinetic, spectroscopic, and structure‐based evidence presented. Hindered bases were proposed to operate by E2 elimination reaction of free base at the carbenium ion. N ‐Hydro‐2,5‐disubstitutedpyrroles were proposed to form the η 5 ‐2,5‐disubstitutedpyrrolyltrichloro‐titanium(IV) coordination complex, which serves as the true quencher. Sulfides, ethers, and silylethers were proposed to operate by first converting the PIB chain ends quantitatively to the onium adduct, which is then decomposed to form exo ‐olefin PIB. Sulfides and ethers were the best performing quenchers of all the types studied, particularly bulky ones such di‐ tert ‐butylsulfide and diisopropyl ether.