Magnetic resonance imaging study of the swelling kinetics of hydroxypropylmethylcellulose (HPMC) in water.

Magnetic resonance imaging has been used to monitor the hydration of hydroxypropylmethylcellulose samples by two-dimensional mapping of properties such as spin density and relaxation times. The measurements were performed at two pH values of water: 2 and 6 and two temperatures 25 and 37 degrees C. It is shown that transport behavior of water into HPMC changes from being almost completely relaxation controlled (case II) at pH=2 to Fickian behavior for pH=6. It was also observed that radial swelling is larger for the system composed of HPMC and water at pH=6 than at pH=2.