No abstract

Proton‐conducting membranes of poly(vinylidene fluoride), PVDF, grafted with styrene and thereafter sulfonated, were investigated by Raman spectroscopy. The depth and surface distribution of polystyrene grafts and crosslinker, as well as the sulfonation efficiency, were determined by using confocal micro‐Raman spectroscopy. Highly grafted samples show homogeneous distribution of grafted material and homogeneous sulfonation. Depth profiles reveal uneven graft distribution for samples with low and intermediate degrees of grafting. In crosslinked samples, the crosslinker concentration in the interior of the film is found to be roughly 50% of the surface concentration. In contrast to what has previously been reported, the sulfonation efficiency is poor at low graft levels and is further inhibited by the presence of divinyl benzene, DVB, as crosslinker. At degrees of grafting above ∼ 60%, the crosslinker does not affect the sulfonation efficiency and a level of 70–90% sulfonation is reached. The matrix polymer structure is found to be largely retained after irradiation, grafting, and sulfonation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3317–3327, 1999

No abstract

No abstract

The luminescence of Eu3+ in a salt–polymer complex, poly(propylene oxide) containing Eu(CF3SO3)3 salt, was studied using broad band and site-selective excitation. Two distinctly different types of local structure around Eu3+ were detected. To investigate and compare the local structure around the SO3CF−3 anions with that around the Eu3+ cations, a Raman scattering study of the SO3 symmetric stretch vibration was performed in the same system. The vibrational data clearly reveal that also the anions are subject to two types of local environment. It is found that neither of the two states can be attributed to ‘‘free’’ (completely solvated) ions, which implies the existence of two different anion–cation configurations. Temperature and concentration dependent studies of the site-selective Eu3+ luminescence and the SO3 vibrational spectrum show that the relative amount of ions in the two states is, within the experimental accuracy, constant. However at elevated temperatures there is a rapid exchange between the two states not found at lower temperatures. The characteristic time scale for the ionic exchange is found to be closely related to the structural relaxation time of the polymer segmental mobility. The findings support the idea that ionic diffusion in salt–polymer complexes is assisted by the local polymer chain mobility which is used in models to explain polymer electrolyte performance.