The polymer PP, which consists of a poly(p-phenylene) backbone with sulfonate eater and dodecyl side groups, is synthesized by a Pd-catalyzed coupling of the 1,3-propanediol diester of 2-dodecyl-5-methyl-1,4-benzenediboronic acid with 2,2’-bis(3,5-di-tert-butylbenzenesulfonato)-4-4’-dibromobiphenyl. Polymers with various molar masses are obtained, which are soluble without aggregation in conventional organic solvents. The good solubility of this rodlike polymer allows the accurate determination of the molar mass by light scattering, osmometry, and SEC with universal calibration. The dependence of the intrinsic viscosity [eta] on the molar mass is determined from both the Mark-Houwink-Sakurada equation and the wormlike chain model. The low value of the persistence length (13 nm) indicates that these polymers are relatively flexible. It is shown that an approximate value of the persistence length, together with the parameters of the Mark-Houwink-Sakurada equation and the wormlike chain model, can be determined using only a single polydisperse sample.