Gel-type polyacrylic resins cross-linked with trimethylolpropanetrimethacrylate: the issue of their nanostructure and molecular accessibility unveiled with a combination of Inverse Steric Exclusion Chromatography (ISEC), ESR and CP MAS 13C NMR spectrometries

Six gel-type functional resins, that is, three poly-DMAA-co-TMPTP (DMAA=N,N-dimethylacrylamide, TMPTP=trimethylolpropyltrimethacrylate) samples with different degrees of cross-linking (0.6, 1.2, 1.7% mol) and three poly-DMAA-co-MA-co- TMPTP (MA=methacrylic acid, ca. 5.5% mol) samples with 1.7, 3.5, and 7% mol cross-linking were investigated with ISEC (inverse steric exclusion chromatography), and ESR and CPMAS (cross polarization magic angle spinning) 13C NMR spectroscopy after swelling in water and other solvents. This unprecedented combination of conceptually independent physicochemical techniques provides a thorough overall consistent picture of the morphology of the resins on the nanometer scale and of the molecular accessibility of the swollen polymer framework to the paramagnetic probe TEMPONE (2,2,6,6-tetramethyl-4-oxo-1- oxypiperidine) and to selected solvents.