A structural study of perfluorosulfonated ionomer (PFSI) solutions in polar solvents such as alcohols, amides, and water using both small-angle X-ray and neutron scattering is presented. Contrast variation methods have shown that the ionomer molecule particles form dense particles of constant scattering length. The study of dilute solutions allows one to evidence the rodlike structure of PFSI solutions. The radius of the cylindrical particles is determined from both the shape and the intensities of the scattering curves. These results are confirmed by the analysis of the asymptotic behavior at large angles of the scattering curves. Typical values for the radii are found to be around 20 Å. The diameter of the rod is shown to be related to the polymer−solvent interfacial energy, whereas the dielectric constant of the solvent acts only on the local order. Mixtures of solvents have been used to check the evolution of the structure with the solvents. The effect of the counterion is also studied. The effect of added salt on the small-angle scattering spectra can be interpreted as due to a decrease of the local order through the disappearance of the interference term and the shape of the particles is not modified.

The colloidal structure of perfluorinated ionomer solutions in polar solvents which are not able to dissolve the neutral polymer analogue is confirmed studying short pendant chain perfluorosulfonated ionomer solutions by small-angle X-ray and neutron scattering. The analysis of the form factor obtained from the “dilute” solution spectra combined with the asymptotic behavior at large q values indicates the existence of rodlike shape aggregates. The radius is found to be 17 Å for aqueous solutions. The effects of the nature of the solvent and of the presence of added salt are studied. The origin of the scattering maximum is attributed to a local ordering between aggregates, and the value of the radius calculated from the peak position using space filling arguments compares well with other determinations. Finally, the study of the evolution of the reduced viscosity against the concentration shows evidence of a strong polyelectrolyte effect.

Maxwell's equations in isotropic optically active media. In particular, the effective optical rotation path length, near index matching, is equal to the Goos-Hänchen shift 9 of the evanescent wave. The limits of this polarimeter, when using a continuous-wave laser locked to a stable high-finesse cavity, should match sensitivity measurements for linear birefringence (3x10 -13 rad) 10 , which is several orders of magnitude more sensitive than current chiral detection limits 7 , transforming the power of chiral sensing in many fields.