Empirical polarity parameters are recommended as useful characteristics for describing the internal and external surface properties of various solid materials, e. g. synthetic polymers, native polymers, inorganic oxides, sol-gel hybrids, and composites. The polarity properties of a macromolecule have been expressed by three independent terms: the α value (the hydrogen bond donating, HBD, capacity or acidity), the β value (the hydrogen bond accepting, HBA, capacity or basicity), and the π* value (the dipolarity/polarizability). These terms can be defined using the Kamlet-Taft solvents parameter set as the reference system. A complex property, XYZ, of a macromolecular material under study, with reference to a standard system (XYZ)0 (i. e. gas phase or a nonpolar polymer), can then be described by a simplified Kamlet-Taft LSE (linear solvation energy) equation: XYZ = (XYZ)0 + sπ* + aα + bβ. a, b, and s are coefficients reflecting the susceptibility of the polarity terms upon XYZ. Empirical solvatochromic polarity parameters [α, β, π*, ET (30)] for synthetic polymers, copolymers, native polymers, inorganic oxidic materials, functionalized silica particles, hybrids, and composite materials have been determined by means of the following solvatochromic probe dyes: 2,6-diphenyl-(2,4,6-triphenyl-1-pyridinio)-4-phenolate (1 a), Michler's ketone (2), dicyano-bis(1,10-phenanthrolin)iron II (3), and a novel aminobenzodifuranone dye (7). The solvatochromic band shifts of these indicators correlate precisely with the Kamlet-Taft solvent parameters α, β, and π*. The results are compared with each other, with related solvent model compounds, and literature values. The relation of the well established ET (30) solvent polarity scale to the Kamlet-Taft parameters α and π* of solid materials is demonstrated. Hence, a general polarity scale for solid materials is suggested.
No takes yet. Share an insight, caveat, or question.
Spange et al. (2000) studied this question.