The Issue of Morphology and Molecular Accessibility of Swollen Gel-type Resins: an Integrated ISEC-ESR-NMR Approach

A number of microporous fairly hydrophilic poly(N,N-dimethylacrylamide-methylenebisacrylamide) (poly-(DMAA-MBAA)) resins (cross-linking degree from 2 to 8%) have been examined with techniques that provide information on the structure on the nanometer scale and molecular accessibility of these materials in the swollen state. Electron spin resonance (ESR), pulsed-gradient-spin-echo nuclear magnetic resonance (PGSE-NMR) spectroscopies, and inverse steric exclusion chromatography (ISEC) gave consistent results in water, tetrahydrofuran (THF), and dichloromethane (DCM). The results are interpreted on the basis of physical models which fit reasonably the experimental data. The resulting equations between the translational diffusion coefficient of the solvent, the rotational correlation time of the spin-probe 2,2,6,6-tetramethyl-4-oxo-1-oxylpyperidine (TEMPONE) dispersed inside the swollen resins, and the polymer chain concentration appear to be promising tools in the design of macromolecular materials for chemical and catalytic applications.