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Synthesis of ring‐shaped polyisoprene
Author(s) -
Madani Abdelaziz El,
Favier JeanClaude,
Hémery Patrick,
Sigwalt Pierre
Publication year - 1992
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.4990270411
Subject(s) - tetrahydrofuran , bicyclic molecule , conjugated system , polymer chemistry , hexane , ring (chemistry) , chemistry , materials science , organic chemistry , polymer , solvent
Cyclization of α,ω;‐dilithiopolyisoprenes has been achieved in hexane solution in the presence of tetrahydrofuran (15% in volume) at −40 to ‐ 50°C. Using as linking agent the non‐conjugated diene 1,2‐bis(isopropenyl‐4‐phenyl)‐ethane, macrocyclic polyisoprenes could be obtained with yields of at least 90%, even for molecular weights as high as 30 000 mol g −1 . With SiCl 4 as coupling agent no gelation occurred and yields of about 70% in cyclic dimers, probably bicyclic, have been observed. These results are compared to those obtained by various authors with α,ω;‐dilithiopolystyrenes or α,ω;‐disodiopolystyrenes and are attributed mainly to the presence, in the polyisoprene case, of predominant cyclic aggregates even at low organolithium concentration.