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Some light on the concept of unreactivity arising from active center association in anionic polymerizations
Author(s) -
Young R. N.,
Fetters L. J.,
Huang J. S.,
Krishnamoorti R.
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.1994.210330213
Subject(s) - monomer , active center , polymerization , work (physics) , aggregate (composite) , diffusion , singlet state , chemistry , glass transition , thermodynamics , diene , polymer chemistry , center (category theory) , chemical physics , materials science , polymer , organic chemistry , physics , catalysis , natural rubber , nanotechnology , excited state , atomic physics , crystallography
A long held assumption in hydrocarbon based anionic polymerization involving organolithiums is that the aggregated species are unreactive and thus serve only as reservoirs from which the active singlet species momentarily emerge to participate in the initiation or propagation events. This work demonstrates that contrary to the notion of aggregate dormancy such species can participate in monomer addition. The approach involved freeze‐dried vitrified polystyryllithium which was found to be reactive toward butadiene and methanol vapors. The sub‐glass transition state of the polystyryllithium eliminates the establishment of the aggregate: singlet equilibrium as a result of the inability of chains to undergo diffusion. Furthermore, it is shown that the lower bound gradient for the dependence of propagation rate on active center concentration, within experimental error, is about 1/5 for the majority of those diene systems where the active center concentration covers at least two decades. A computer evaluation of the propagation rate: active center data was done with the aim of testing and determining the equilibrium constants of these aggregated systems.