Free-Radical and Singlet-Oxygen Mobility in Cotton Probed by EPR Spectroscopy

Abstract

Spin probe EPR experiments using TEMPO and TEMPOL are reported on dry cotton. The spectra are in the slow tumbling region with τrot ∼ 1 ns, the line width is found to be affected by Heisenberg spin exchange and aggregation of the radical. To probe the entire amorphous zone of cotton, ethanol and water are used to deposit the radicals; to probe the fiber surface specifically toluene was used. Analysis shows that in both regions the viscosity is 30 cP and that the fiber surface is an amorphous layer with a depth of approximately 2 nm. The radical motion follows normal liquid theory with a diffusion rate constant of 2 × 108 mol-1 L s-1. A small proportion of the radicals deposit to an area of much higher viscosity. The classical spin probe method is extended via a simple electron spin polarization experiment. This involved irradiation of the sample and analysis of the radical−triplet mechanism polarization of TEMPOL/O2, which indicates 1O2 diffuses with a similar rate constant.

Dynamic electron polarization created by the radical-triplet pair mechanism: Application to the studies on excited state deactivation processes by free radicals

“…Conceming this site selectivity, Batchelor reported that TEMPO doped in cotton could be used as O2(1Ag) probe and diffusion motion of O2(lAg) in inhomogeneous media was discussed [54].…”

Hierarchical porous structures in cellulose: NMR relaxometry approach

“…A hierarchical porous structure formed during the assembly of cellulose chains into a cellulose material, which occupies a large volume of the cellulose material [5,10]. The hierarchical pores in cellulose material can accommodate liquid, which is the advantage of cellulose materials in the field of electrolyte reservoir, separation membranes, facial mask and scaffold for tissue engineering [11][12][13][14][15][16][17][18][19].…”

“…Cellulose materials soaking in liquids are necessary when cellulose materials are used in the fore-mentioned fields [11,12,[14][15][16][17][18][19]. In addition, activation of cellulose (generally by soaking cellulose in certain liquid or stewing cellulose at high temperature) is necessary before dissolving cellulose in many solvent systems, such as N,N-dimethylacetamide (DMAc)/LiCl [2,9].…”

Free Radical Motion in the Supramolecular Structure of Nylon 6,6 and Elastane, Studied by Quantitative Spin Probing

“…Spin probing experiments, where a stable nitroxide radical is doped into the fiber and its EPR spectrum recorded, give useful information. [2][3][4] Here a detailed spin probe study of two important synthetic fibers, Nylon 6,6 and Elastane, is reported. Nylon 6,6 is formed from polyhexamethylenediamide, 5 and Elastane is formed from polyurethane-poly(ethylene glycol) copolymers: 6 Nylon 6,6 is 50% crystalline, as measured by X-ray diffraction, 5,7 and hence is 50% amorphous.…”