Self-Diffusion of End-Capped Oligo(ethylene glycol)s in Poly(vinyl alcohol) Aqueous Solutions and Gels

We have studied the self-diffusion of a series of end-capped ethylene glycol and oligo(ethylene glycol)s in poly(vinyl alcohol) aqueous solutions and gels by pulsed-gradient spin echo NMR spectroscopy. The end groups of the diffusants include small flexible groups (methyl, ethyl, hexyl) and bulky rigid groups (tert-butyl and aromatic groups). The effect of the size and geometry of the end groups on the self-diffusion coefficients of the derivatives of ethylene glycol and of oligo(ethylene glycol)s is investigated. The diffusion data are analyzed with several physical models of diffusion based on different physical concepts to test their applicabilities. The variation of the parameters used in these diffusion models with the size and geometry of the diffusants is also discussed.