Rigid‐rod polyelectrolytes based on poly(p‐phenylene sulfonic acid)

Abstract

Abstract The synthesis and characterization of polyelectrolytes, composed of a shape persistent poly(p‐phenylene) backbone with regularly attached sulfonic acid‐ and n‐alkyl residues, is described. Polymers were obtained by Pd‐catalyzed coupling of substituted p‐phenylene‐bis‐boronic acid esters with 2,5‐dibromobenzenesulfonates or 4,4′‐dibromodiphenyl‐2,2′‐disulfonates, followed by saponification of the sulfonates. The polymers were found to have number average contour lengths ( L n ) betwen 23 and 155 nm. The polymer sulfonic acids behave as strong acids and are soluble in water as their tetramethylammonium salts. The concentration dependence of the viscosity of aqueous solutions of the salts does not follow the behavior seen for conventional polyelectrolytes. The polymers show lyotropic behavior at low to moderate concentrations. Polymers with long alkyl substituents, if spread as monolayers on a Langmuir trough and subject to the Langmuir‐Blodgett technique, give LB‐multi‐layers, which have been characterized by X‐ray reflectometry. As a model compound, sodium 4,4″‐dimethyl‐1,1′:4′,1″‐terphenyl‐2′‐sulfonate was obtained as single crystal and its X‐ray structure is described.