Empirical polarity parameters for various macromolecular and related materials

Abstract

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.

Measuring the Micro-Polarity and Hydrogen-Bond Donor/Acceptor Ability of Thermoresponsive N-Isopropylacrylamide/N-tert-Butylacrylamide Copolymer Films Using Solvatochromic Indicators

“…The polarity (or more precisely the micro-polarity experienced by the probes) of the NIPAM/NtBA films cover a relatively small section of the E T (30) 18 However, it would be incorrect to judge the polarity of NIPAM/NtBA copolymers as having the same polarity as primary alcohols because the alcohols are generally very good hydrogen-bond donors. It is more correct, taking into consideration the polymer structure and the measured Kamlet- Taft 37,42 Within the α-β-π* model, the observed differences are more significant since PVP (α = 0.01, β = 0.93, π * = 0.93) 37 is an aprotic polymer, PEO (α = 0, β = 0.65, π * = 0.86) 37 is an amphiprotic polymer, whereas PVA ((α = 0.29, β = 0.52, π * = 1.11) 26 and NIPAM/NtBA copolymers are more protic systems. Thus, the solvatochromic α-β-π* method offers a more discriminating method for assessing the polarity of hydrophilic polymers than by simple polarity or water contact angles.…”

“…This is important because, although the gross polymer polarity decreases with NtBA fraction, the heterogeneity of the local microenvironment (polarity distribution) increases. 37 This is therefore a useful measure of film heterogeneity.…”

Polarity Assessment of Thermoresponsive Poly(NIPAM-co-NtBA) Copolymer Films Using Fluorescence Methods

“…For in-situ analysis of the bulk properties of polymer films, various optical techniques can be employed including vibrational, fluorescence, and UV-Visible absorption spectroscopy [3,4]. In particular, fluorescence spectroscopy has received considerable interest due to its high sensitivity, selectivity, and non-destructive characteristics.…”

Empirical surface polarity parameters for native polysaccharides

“…[15][16][17] Empirical polarity parameters of synthetic macromolecules were also rarely reported. [18,19] A reason for the deficit of reasonable polarity parameters for polysaccharides may be the lack of suitable polarity indicators which do adsorb appropriately to the relevant microenvironment.…”

“…The Kamlet-Taft parameters seem to be very useful in describing the manifold polarity properties of organized assemblies [17] or of surfaces, [19,21] either because they can easily be transmitted into the E T (30) scale by Eq. (10) [10] as well as into other useful solvent polarity scales such as the acceptor number (AN) and donor number (DN) scale Full Paper: The empirical Kamlet-Taft solvatochromic polarity parameters a, b, and p* as well as calculated Reichardt's E T (30) values are presented for microcristalline cellulose, cellobiose, chitine, amylose, amylopectine, and glycogene.…”