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Hydrocarbon‐soluble difunctional organolithium anionic initiators. A gas–liquid chromatographic study of the reaction of sec ‐butyllithium with m ‐divinylbenzene
Author(s) -
Sanderson Ronald D.,
Roediger Andrew H. A.,
Summers Gabriel J.
Publication year - 1994
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1994.210350308
Subject(s) - triethylamine , butyllithium , chemistry , divinylbenzene , anionic addition polymerization , polymerization , polymer chemistry , organic chemistry , copolymer , polymer , styrene
Quantitative gas–liquid chromatography provides an efficient, novel technique for the kinetic study of the reaction between sec ‐butyllithium and m ‐divinylbenzene. The reaction of stoichiometric amounts of ultra‐high purity sec ‐butyllithium with pure m ‐divinylbenzene at −23°C produces an anionic initiator, 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene, 2 , without traces of monofunctional and polyfunctional impurities. The relative rates of formation of 2 with and without the presence of Lewis base, triethylamine, or Lewis acid, diethylzinc, were studied by gas–liquid chromatography. The presence of diethylzinc reduces the activity of sec ‐butyllithium to such an extent that the reaction did not proceed beyond the monofunctional component stage, that is, the formation of m ‐1‐lithio‐3‐methylpentylvinylbenzene, 1 . The reaction of sec ‐butyllithium with m ‐divinylbenzene at −79°C with a 10mol% ratio of triethylamine to sec ‐butyllithium yielded a homogeneous product with composition of 94% difunctionality and 6% monofunctionality, with the total disappearance of m ‐divinylbenzene as observed by GLC. However, precipitation due to agglomeration was observed at 25°C at 100% conversion. The high purity 1,3‐bis(1‐lithio‐3‐methylpentyl)benzene initiator, 2 , is effective for the polymerization of 1,3‐butadiene and allows the synthesis of polybutadienes with predictable molecular weights and narrow molecular weight distributions. Depending on the polymerization solvent, polybutadienes with microstructures ranging from 9 to 13% 1,2‐vinyl content were observed by 1 H NMR analysis and FTIR spectroscopy. However, the presence of diethylzinc retards the rate of polymerization of 1,3‐butadiene, without any change in polymer microstructure. Triethylamine enhances the rate of 1,2‐enchainment without significant reduction in the 1,4‐enchainment of polybutadiene.