Multivariate data analysis methods are being applied in conjunction with vibrational spectroscopic measurements to gain insights into structure and physical properties of ionomer materials.  Infrared and confocal Raman spectroscopy techniques are being adapted to investigate (i) fluorinated ionomer standards that span a range of equivalent weight and (ii) membrane samples with varying tensile properties.  Partial least squares (PLS) modeling applied to mid-infrared spectral data sets measured using the attenuated total reflection (ATR) technique is robust in predicting ionomer equivalent weight from measurements on calibration samples.  The experimental approach, statistical uncertainties and extension to confocal Raman experiments will be discussed.  

In relation to membrane structural and tensile properties, vibrational spectra that follow transitions between dispersion, gel and solid membrane ionomer forms are being scrutinized.  Least-squares modeling and principal component analysis (PCA) used in combination enhances the ability to resolve spectral features associated with molecular components of the sample that evolve during processing (Figure 1) and to quantitatively track changes in composition over time.  Figure 1 shows results from confocal Raman tracking of aqueous Nafion ionomer dispersion through a gel phase.  PCA and least-squares modeling were applied to data within the shaded region to extract the indicated spectral components.  For membrane processed under different thermal treatments, PLS regression is being applied to examine the correlation between tensile strength and molecular scale structure probed by vibrational spectra.