Electrochemical, Pulsed-Field-Gradient Spin-Echo NMR Spectroscopic, and ESR Spectroscopic Study of the Diffusivity of Molecular Probes inside Gel-Type Cross-Linked Polymers

• Published in: Chemistry : a European journal 2007-01, Vol.13 (8), p.2392-2401
• Main Authors: Corain, Benedetto, D'Archivio, Angelo A., Galantini, Luciano, Lora, Silvano, Isse, Abdirisak A., Maran, Flavio
• Format: Article
• Language: English
• Subjects: diffusion; electrochemistry; gels; polymers
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200601276

The permeability of five gel‐type synthetic resins, obtained by polymerization of 1‐vinylpyrrolidin‐2‐one cross‐linked with N,N′‐methylenebisacrylamide (1, 2, 3, 4, and 5 wt %) and swollen by N,N‐dimethylformamide (DMF), has been analyzed. The diffusion of 2,2,6,6‐tetramethyl‐4‐oxo‐1‐piperidinyloxyl (TEMPONE) was studied by ultramicroelectrode voltammetry. Similar measurements were performed for solutions of non‐cross‐linked poly(vinylpyrrolidone) in DMF. To provide information on the rotational mobility of TEMPONE and the translational mobility of DMF, electron spin resonance (ESR) spectroscopic and pulsed‐field‐gradient spin‐echo nuclear magnetic resonance (PGSE‐NMR) spectroscopic experiments, respectively, were carried out. Comparative analysis of the results obtained by electrochemical, ESR spectroscopic, and PGSE‐NMR spectroscopic measurements showed that diffusivity inside the polymer framework is significantly affected by the extent of cross‐linking, the size of the diffusing probe, and the presence of electrolytes. The diffusivity of molecular probes inside polymer frameworks swollen by DMF was successfully studied by using a combined ultramicroelectrode voltammetry, ESR spectroscopy, and pulsed‐field‐gradient spin‐echo NMR spectroscopy approach. The results are in agreement with an obstruction mechanism of diffusion (D; see figure).