An Investigation of Polymer Diffusion in Hydrogel Laminates Using Near-Field FTIR Microscopy

The role of diffusion in gel/gel adhesion was examined by near-field FTIR microscopy. Using a near-field FTIR microscopy technique, compositional maps were obtained with improved spatial resolution and enhanced signal to noise ratio. With this technique, the resolution was enhanced by about a factor of 5. Polymer chain diffusion across a gel/gel interface was a substantial mechanism of adhesion. Diffusion of poly(ethylene glycol) (PEG) free chains across poly(acrylic acid) (PAA) gels was investigated. The diffusivity of PEG was on the order of 10 -8 to 10 -9 cm 2 /s for these swollen polymer gels. PEG diffusivity in PAA gels scaled to M -0.41 . This was similar to values reported for PEG diffusion in aqueous solution.