The far‐infrared spectra of polystyrene methacrylic acid/(PSMA) ionomers have been investigated as a function of cation and ion‐site concentration to obtain spectroscopic evidence of domain formation. A far‐infrared band, due to the vibration of a higher‐order cluster, is found at 170 cm−1in Na+‐form PSMA. This band, which is observed in addition to the known cation‐motion bands, is assigned to the vibrations of aggregates involving many cations and anionic sites close together, and the results are discussed in light of ion aggregation models.
The far-infrared spectra of the Li+, Na+, K+, Cs+ salts and acid forms of polyelectrolytic ethylene-methacrylic acid copolymers have been examined in the 800–33-cm−1 region at ambient and low temperatures. A broad band, which shifts to lower frequency as the cation mass is increased, is attributed to cation motion in anionic fields, and the appearance of a low frequency band, whose intensity is related to the cation properties, is assigned to perturbed skeletal motions of a neighboring polymer segment. Models are proposed and analyzed for the vibrational modes involving ion motion. The vibrational force constants for aggregate distortion, as calculated from the observed ion-motion frequencies, are in agreement with such constants computed here employing an ion-multipole potential energy function which does not use these experimental data. The spectral and theoretical results are considered in terms of the molecular interactions of importance in polyelectrolytes and in the physical properties of these materials.
Frequencies of the quantized motion of cations encaged in cyclic poly ether (crown) systems have been determined from solvent-and anion-independent bands in the far ir spectra of dissolved crown-alkali-metal-salt complexes in pyridine and DMSO. The analysis of the forces with which the cations are encaged shows that the Na+-crown and K+-crown forces are nearly equal for dibenzo-18-crown-6, and that cation selectivity in these cases does not derive from differences in ion-crown encagement forces. The forces between cations and solvent molecules (DMSO, pyridine) are evaluated from cation-motion frequencies which are shown to be independent of the nature of the counterion in several salt solutions. The combined results from solvated and crown-encaged cations are shown to establish the basis for evaluation of molecular scale forces involving antibiotic-cation complex species postulated to be responsible for ion-selective transport properties. n work recently reported from this laboratory2-5 and others,6-16 it has been demonstrated that vibrational bands due to quantized motion of simple ions in solu-
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