NMR EVIDENCE OF ANOMALOUS MOLECULAR-DIFFUSION DUE TO STRUCTURAL CONFINEMENT

Using the field gradient NMR technique, anomalous molecular diffusion in a porous host matrix of polypropylene could be followed over a subs tantial range of observation times. The experimentally determined time exponents of anomalous diffusion are found to decrease with decreasin g pore filling factors, indicating an enhancement of molecular confine ment. For sufficiently large observation times normal diffusion is obs erved and the effect of confinement results in a mere reduction of the effective diffusivity, which is independent of the given molecular sp ecies.