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Anionic ring‐opening polymerization of cyclodisilazanes, 3 . Influence of the silicon substituent on the kinetics of polymerization
Author(s) -
Cazalis Chrystelle,
Mingotaud AnneFrançoise,
Soum Alain
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021981109
Subject(s) - chemistry , polymerization , reactivity (psychology) , monomer , polymer chemistry , substituent , anionic addition polymerization , kinetics , ring opening polymerization , living polymerization , reaction rate constant , cationic polymerization , ionic polymerization , tetrahydrofuran , bulk polymerization , chain growth polymerization , photochemistry , radical polymerization , medicinal chemistry , organic chemistry , polymer , medicine , physics , alternative medicine , pathology , quantum mechanics , solvent
The kinetics of the anionic ring‐opening polymerization of several cyclodisilazanes substituted with different groups on silicon atoms has been investigated in toluene/tetrahydrofuran (THF) using benzyllithium as initiator. Two different behaviours were observed: for hindered substituents (phenyl or allyl), the polymerization is not living; for less hindered groups, the polymerization is living but the rate constants differ markedly from one cyclodisilazane to another. They vary from 9 × 10 −4 L · mol −1 · s −1 for D NMe Et D NMe 3 to 0,1 L · mol −1 · s −1 for D NMe 2Vi D NMe (8) . These variations show that the presence of vinyl groups on the monomers tremendously increases the rate of polymerization. In order to discriminate the monomer reactivity from the active center reactivity, a model reaction between lithium silylamides and triethylchlorosilane has been kinetically studied (each lithium silylamide was chosen to modelize one particular active center). Contrary to the corresponding monomers, the less hindered is the silylamide, the faster is the reaction. Thus, the difference of reactivity between the monomers and the reactive center models is so high that the polymerization of cyclodisilazanes can be considered as principally controlled by the reactivity of the monomers.