REDOX-ACTIVE LIQUID-CRYSTALLINE IONOMERS .1. SYNTHESIS AND RHEOLOGY

Liquid-crystalline (LC) copolymers with redox-active groups were prepared by copolymerization of mesogenic and ferrocene-containing monomers (up to 10%). In these copolymers the ferrocene groups can be oxidized reversibly to prepare ionomers, while retaining the LC phase. It is thus possible to vary the amount of ionic groups in the ionomers by a redox reaction. The oxidized (charged) polymers show a strong excess X-ray scattering at small angles. This is typical for ionomers and is assigned to the scattering of ionic aggregates. Dynamic mechanical measurements show that these aggregates are effective as crosslinking points. Thus an oxidation-reduction reaction can be used to transfer an uncrosslinked polymer (reduced ferrocene groups, uncharged) reversibly into an oxidized polymer that acts like a weakly crosslinked gel.