Triethyloxonium hexachloroantimonate initiation

In 1971 Lyudvig et al. [97] reported an investigation of the polymerization of 1,3-dioxolane using precision purification of reactants and Et3 0 SbCl6 as initiator. Under these conditions polymerization with different initial monomer concentrations are reported to take place without any induction period. Lyudvig et al. report that the polymerization is first order with respect to both monomer and initiator concentration. Polymerization of 1,3-dioxolane is a reversible process. The final kinetic equation takes a form similar to eqn. (6). A UV spectroscopic method was used to investigate the nature of the active centre in the polymerization. Very briefly, what these workers found was that the maximum they observed for the polymerizing mixture was different from that which could be attributed to a simple cyclic oxonium ion. Hence they propose that the active centre has the polymeric tertiary oxonium ion structure 

They suggest two possible pathways for the polymerization reaction, viz. 

Lyudvig et al. [97] believe that in the presence of water the mechanism of the reactions are different. An induction period is then observed, i.e., polymerization is inhibited. 

Yamashita [128] reports that the kinetics of polymerization of 1,3-dioxolane initiated by BF3. Et2 O are quite complex and that initiation is not a simple reaction. In 1973 Rozenberg et al. [130] reported a kinetic study of such a polymerization in CHjClj solution. They e ain found an induction period, but this time stated that the acceleration is the result of the autocatalytic action of the macromolecules formed. Their conclusions are based (i) on the relationship of the rate coefficients of BF3. Et2 0 reactions with cyclic monomer or with polymer chain and (ii) on the decrease of the induction period on addition of polymer or methylal to a polymerizing mixture. The mechanism of initiation suggested is 

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As far as the polymerisations of DCA other than DXL by non-protonic initiators are concerned, Kops and Spanggaard [11] favour the ring expansion mechanism for the dimerisation and polymerisation of the cis- and tnms-7,9-dioxabicyclo[4.3.0] nonanes by phosphorus pentafluoride or triethyloxonium hexachloroantimonate, although they have not obtained any definitive evidence for it. 

More recently (55) triethyloxonium hexachloroantimonate has also been used as an initiator of the polymerisation of this monomer, and its dissociation constant determined as 5.3 x 10 5 M at 20° C in methylene chloride. Penczek (54) has also studied the dissociation of l,3dioxolan-2-ylium hexafluoroarsenate and hexa-fluoroantimonate,... 

Lyudvig, Rozenberg et al. (41) made a study of the kinetics of THF polymerization initiated by triethyloxonium hexachloroantimonate. 

Carbon-14-labelled triethyloxonium hexachloroantimonate, [( 3115)2002115] (SbClg)", 18 (specific activity 1.15 x 10 Bq g ), has been obtained by treating the C-labelled ( 2115)20 Sb l5 complex with ethyl chloride. The salt was used to clarify the mechanism of initiation of polymerization of 2,3,4-tri-O-methyl-L-glucosane (19) , since it has been noted" " " that the incorporation of the radioactive label into the polymer increases with the increase in the degree of conversion of the monomer (at 10. 5% of the equilibrium yield of the polymer, 2.5% of the initial radioactivity of 18 has been... 

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