The cationic ring-opening polymerization of 7-tetradecene oxide with methyl trifluoromethansulfonate. An investigation of the mechanism and the kinetics by means of H-1, C-13 and F-19 NMR

The polymerization of a mixture of cis (ca. 30%) and trans (ca. 70%) isomer s of 7-tetradecene oxide (7-TDO) with methyl trifluoromethansulfonate (meth yl triflate) as initiator has been investigated. The main reaction products afforded during the polymerization were a linear polyether, a cyclic dimer [2,3,5,6 tetra(n-hexyl)dioxane], and 7-tetradecanone. The ketone is formed both via pinacol rearrangement of the monomer and a transfer reaction when all the monomer is consumed, and is favoured by an increase of temperature . Kinetic studies on the ring opening polymerization of this system were pe rformed by means of H-1 and F-19 NMR spectroscopies. Approximate rate const ants of initiation (ki) for the cis and the trans isomers were determined a t 298, 314 and 329 K in bulk, and at 298 K in C6D6 The reaction time of the cia isomer is faster than that of the trans isomer, with an initial molar reactivity ratio of about 11:1 at 298 K, and of about 7:1 at 329 K tin bulk ). The activation energies of the initiation reaction for the cis and the t rans isomers were calculated to be 59 and 73 kJ/mol, respectively. By means of H-1-, F-19- and C-13-NMR the structure of the propagating species is re asonably well identified as an oxonium macroion rather than a linear trifli c macroester. (C) 1999 Published by Elsevier Science Ltd. All rights reserv ed.