화학공학소재연구정보센터
Macromolecular Rapid Communications, Vol.21, No.10, 643-659, 2000
Empirical polarity parameters for various macromolecular and related materials
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 alpha value (the hydrogen bond donating, HBD, capacity or acidity), the beta value (the hydrogen bond accepting, HBA, capacity or basicity), and the pi* 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) + s pi* + a alpha + b beta. a, b, and s are coefficients reflecting the susceptibility of the polarity terms upon XYZ. Empirical solvatochromic polarity parameters [alpha, beta, pi*, E-T(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-pyridino)-4-phenolate (1a), 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 alpha, beta, and pi*. 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 a and pi* of solid materials is demonstrated. Hence, a general polarity scale for solid materials is suggested.