Mesomorphic State of Poly(vinylpyridine)-Dodecylbenzenesulfonic Acid Complexes in Bulk and in Xylene Solution

Abstract

Theoretically, lyotropic behavior of flexible polymers can be induced by associating the polymers with a large amount of long-tail surfactants leading to bottle-brush type conformations in suitable solvents. To address this and related questions, complexes of poly(2-vinylpyridine) (P2VP) and poly(4-vinylpyridine) (P4VP) with p-dodecylbenzenesulfonic acid (DBSA), characterized by FT-IR, were investigated in the bulk and in xylene, i.e., a good solvent for the alkyl side chains. At a 1:1 molar ratio of vinylpyridine monomer and DBS, the polymers are shown by FT-IR to be almost completely protonated. In the bulk, the complexes form mesomorphic layer structures which have been characterized by polarized optical microscopy and by both wide- and small-angle X-ray scattering. In the xylene solutions, birefringence indicating liquid crystallinity is observed for concentrations of the fully protonated P4VP-(DBSA)(1.0) complex of ca. 50% (w/w) and higher. In contrast, for P2VP(DBSA)(1.0), this is only observed at complex concentrations of ca. 70% (w/w) and higher. The mesomorphic behavior of P4VP(DBSA)(1.0) in xylene was further demonstrated by SAXS.