Influence of chain length on the molecular dynamics of an aliphatic ionene

An aliphatic random copolymer ionene (a cationic polyelectrolyte with N + in the repeat unit), was fractionated with the continuous polymer fractionation and investigated for its molecular weight dependent properties. The fractions were analyzed with GPC and capillary viscometry for their molecular weight. Glass transition temperatures were determined with DSC and a strong molecular weight dependence was observed, but no influence in the ionic conductivity was observed. The temperature dependency of ionic conductivity in ionenes is described.

About 340 g of a cycloaliphatic ionene (see formula given in the introduction) were fractionated by a continuous countercurrent extraction method (CPF). The efficiency of the separation was checked by viscometry and gel permeation chromatography (GPC). Ten different fractions with number average molecular masses between 16 000 and 29 000 D were obtained and their glass transition temperatures T g determined by differential scanning calorimetry (DSC) for their bromide and tetrafluoroborate salts. No molecular weight dependence of T g was found, in contrast to recently reported results with aliphatic ionenes, where - in case of the bromide - T g increases with rising molecular weight.