Macroion‐pairs and macroions in the kinetics of polymerization of hexamethylene oxide (oxepane)

Cationic polymerization of oxepane (hexamethylene oxide) (1) in CH2Cl2 and C6H5NO2 as solvents was initiated with 1,3‐dioxolan‐2‐ylium hexafluoroantimonate (2). Dissociation constants (KD) of the ion‐pairs of polyoxepane into ions were measured: KD (in CH2Cl2, T = 25°C) = 2,8·10−5 mol·l−1 [ΔHD = −3,8 kJ·mol−1 (−0,9 kcal·mol−1), ΔSD = −98 J·mol−1·K−1 (−23,4 cal·mol−1·K−1)]; KD (in C6H5NO2, T = 25°C) = 1,6·10−3 mol·l−1 [ΔHD = −7,1 kJ·mol−1 (−1,7 kcal·mol−1), ΔSD = −78 J·mol−1·K−1 (−18,7 cal·mol−1·K−1)]; these values are close to those of the ion‐pairs of polytetrahydrofuran. Rate constants kp+ and kp±, determined from the kinetic measurements for degrees of dissociation of macroion‐paris ranging from 0,02 to 0,21 (in CH2Cl2) and from 0,09 to 0,7 (in C6H5NO2), were found to be identical within an experimental error of kinetic measurements. The activation parameters of propagation were measured and their dependences on the polarity of the polymerization mixtures are discussed.