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Dilithium initiators based on 1,3‐bis(1‐ phenylethenyl)benzene. Tetrahydrofuran and lithium sec ‐butoxide effects
Author(s) -
Quirk Roderic P.,
Ma JingJing
Publication year - 1991
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.4990240402
Subject(s) - tetrahydrofuran , dilithium , polybutadiene , lithium (medication) , polystyrene , chemistry , cyclohexane , anionic addition polymerization , polymer chemistry , benzene , styrene , molar mass distribution , polymerization , butyllithium , copolymer , organic chemistry , polymer , solvent , ion , deprotonation , medicine , endocrinology
Abstract The adduct (3) from 2 moles of sec ‐butyllithium with 1,3‐bis(1‐phenyl‐ethenyl)benzene has been prepared and evaluated as a hydrocarbon‐soluble, dilithium initiator for butadiene and styrene polymerization in cyclohexane or benzene solution. Under high vacuum conditions with purified reagents, bimodal molecular weight distributions are observed for polybutadienes with M n < 150 × 10 3 g/mol and for polystyrenes with M n < 50 × 10 3 g/mol; monomodal distributions are observed only for higher molecular weights. Addition of tetrahydrofuran ([THF]/[Li] = 14 to 32) or preformed lithium sec ‐butoxide ([LiOBu]/[3] = 1·1) produces narrow, monomodal molecular weight distributions even at M n = 26·2 × 10 3 g/mol polybutadiene and at M n = 10 × 10 3 g/mol for polystyrene. Added lithium sec ‐butoxide is the preferred additive since high 1,4‐polybutadienes are obtained. These results provide an explanation for the contradictory results reported previously; under less rigorous experimental conditions, oxygen and hydroxylic impurities can form lithium alkoxides in situ .