Transport of a poly(ethylene oxide) solution through porous coated silica studied by spin labelling

Poly(ethylene oxide) (PEO) chains of molecular weight 4000 have been labelled at their free end by a nitroxide free radical and adsorbed on silica in cyclohexane. A solution of PEO 10 000 was allowed to flow through the impregnated silica in an Electron Paramagnetic Resonance spectrometer and the decay of the signal recorded as a function of time. The exchange of the short chains by the longer ones and the transport through the quenched disorder proceeds linearly with time. This observation could be characteristic of a diffusion mechanism similar to the Darcy law as the limiting factor of the whole process in the time regime used.