The initiation process in the polymerization of tetrahydrofuran with carbonium ion salts

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Abstract
The initiation process for the polymerization of tetrahydrofuran with (C6H5)3C+SbCl6− has been studied. Two mechanisms have been considered: a cation‐addition process, and a process in which tetrahydrofuran donates a hydride ion to the cation of the initiator to form triphenylmethane. The biscarbonium salt [(C6H5)2C+C6H4CH2]2(SbCl6−)2 has been synthesized and used to initiate the polymerization of tetrahydrofuran. The results are consistent with the hydride‐ion mechanism but may be inconclusive because of chain transfer. NMR experiments with 0.05–0.2M solutions of initiator in tetrahydrofuran show that triphenylmethane is rapidly produced in an amount equal to the molar amount of initiator originally present. Some NMR evidence for the presence of an acetal end group in the polymer has been obtained. It is concluded that the initiation process in this system definitely involves the formation of triphenylmethane, although a detailed, unique mechanism cannot be selected at this time.