Structural studies on cationic poly{9,9-bis[6-(N,N,N-trimethylammonium) alkyl]fluorene-co-1,4-phenylene} iodides in aqueous solutions in the presence of the non-ionic surfactant pentaethyleneglycol monododecyl ether (C12E5)

Two cationic conjugated polyelectrolyte poly{9,9-bis[6-(N,N,N-trimethylammonium)alkyl] fluorene-co-1,4-phenylene} iodides in aqueous solution in the presence of the non-ionic surfactant pentaethyleneglycol monododecyl ether (C12E5) were studied using optical absorption and fluorescence, NMR, and small-angle neutron scattering (SANS) with a model of randomly arranged core-shell cylinders in a solvent. The polymers differed in both the size of the aromatic backbone and the length of the alkyl side chains. In agreement with studies on related conjugated polyelectrolytes, optical observations indicate that the surfactant breaks up clusters of the polymer and produces solutions of mixed polyelectrolyte-surfactant aggregates. The SANS data are in accord with the idea of dissolution and show that with C12E5 surfactant these polymers form long worm-like particles which contain rigid segments with the diameter of 5 nm. With the ternary system involving the polymer with a larger backbone, longer rigid segments were observed, for which a typical value of > 60 nm was calculated. In contrast, for the smaller polymer the value is around 45 nm. This difference is rationalized on the basis of the difference in polymer size.