Magnetic Resonance Imaging in Characterisation of Polymer Films

Diffusivity and distribution of water in random copolymer films of butyl methacrylate and methacrylic acid swollen in water have been investigated using magnetic resonance imaging (MRI) and NMR relaxation techniques. The relative contributions of the protons of the polymer matrix and bound water have been analyzed using 1H NMR spectra and MRI data of the swollen films. Pulse Field Gradient (PFG) NMR experiments have been carried out in parallel to the MRI studies. The results have been discussed with reference to published MRI data for water in a number of polymer materials. The free induction decay (FID) and the spin-spin relaxation times (T2) data for water saturated polymer films correlated well with the MRI intensities for the same samples. The results show that by varying the hydrophobic/hydrophilic comonomer ratios in the polymers, the water ingress can be changed. MRI data show how to monitor drying process. Moisture profiles and relaxation data were obtained during film drying. The time dependences of the image slices intensity for the drying films were fitted by a single-exponential function with an average time constant as k = −0.02 min−1.

Keywords: Copolymer swollen films, Evaporation, Free induction decay (FID), Fourier transform (FT), Hydrophobic/hydrophilic ratio, Magnetic resonance imaging (MRI), NMR spectra, Pulsed Field Gradient (PFG) NMR, Spin-spin relaxation time T2, Stimulated echo (STE), Water.