Claudine E. Williams

Microstructure of the ionic aggregates in telechelic ionomers

Abstract Extended X-ray absorption fine structure (EXAFS) investigations of various types of zinc-neutralized telechelic ionomers have evidenced large differences in the degree of local order within the aggregates. Among the parameters influencing the microstructure, it is shown that the conditions of neutralization play an important role.

Halato-telechelic polymers. XIII. Viscoelastic properties and morphology of low molecular weight polybutadiene bearing alkaline carboxylate end-groups

Abstract When end-capped by alkaline carboxylate groups, a low molecular weight polybutadiene ( M n = 4600 ) behaves as a thermorheologically simple polymer. A secondary relaxation characteristic of the thermal dissociation of the ionic domains is observed in agreement with an Arrhenius-type temperature dependence. Although alkaline carboxylates generally impart a less elastic behaviour to polybutadiene than alkaline earth carboxylates, sodium carboxylate end-groups enjoy a very large degree of association in contrast to all the other alkaline and alkaline earth carboxylates. As a result, sodium carboxylates stabilize a polymer network as efficiently as calcium carboxylates, in spite of the difference in cation valency. The main structural features deduced from dynamic mechanical measurements are supported by the phase morphology as investigated by SAXS. Sodium carboxylates are observed to form the biggest ionic domains with an approximate radius of 12 A, and to promote light dimensional extension of the chains in agreement with the larger interdomain distances.

Weak Temperature Dependence of Structure in Hydrophobic Polyelectrolyte Aqueous Solution (PSSNa): Correlation between Scattering and Viscosity

We study in this paper, either in the semidilute regime by small angle scattering or in dilute and semidilute unentangled regimes by viscosimetric measurements, the influence of temperature on the structure of aqueous solutions of an hydrophobic polyelectrolyte, poly(styrene-co-sodium styrene sulfonate). There is a strong consistency between the two methods: the very weak dependence over temperature at high chemical charge is increased for lower charge fractions, i.e., when hydrophobicity is increased. The solvent quality is thus modified, whereas, for comparison, the hydrophilic polyelectrolyte poly(acrylamide-co-sodium-2-acrylamido-2-methylpropane sulfonate), shows a structure totally independent of temperature, for all the charge fractions.

Small angle X-ray scattering study of phase separation in glasses using a new position sensitive detector

Abstract A recent study by s small angle X-ray scattering (SAXS) of phase separation in a borate glass agreed with the predictions of statistical theories for the demixing process. Here, additional data on the B 2 O 3 PbOAl 2 O 3 system, obtained with synchrotron radiation, are reported. The heat treatment of the sample is performed in situ and the SAXS intensities are measured using a new one-dimensional position sensitive detector. Experimental SAXS data have been collected for different durations of isothermic treatment, in the middle and near the boundary of the miscibility gap. The data suggest the general validity of the dynamical scaling hypothesis of the statistical theory of phase separation in glass systems.

Structure of Ionomers : Use and Abuse of Saxs

This talk will concentrate on a critical evaluation of the structural data obtained by Small Angle X-Ray Scattering (SAXS) in the field of ionomers. By no means a review paper, it will be illustrated by a few recent results on some model systems.