The mucoadhesive properties of a,p poly(N-hydroxyethyl)-DL-aspartamide (PHEA) and alpha,beta-polyaspartylhydrazide (PAHy) have been investigated using attenuated total reflection infrared (ATR-FTIR) spectroscopy. In particular, films based on these polymers have been contacted with a mucin solution at pH 7 and, the interfacial interaction and interpenetration between the glycoprotein and PREA or PAHy have been studied by analysing the ATR-FTIR spectra. A diffusion model using a solution of Ficks' second law has been employed to determine the diffusion coefficient of water into polymeric films as a consequence of interdiffusion which occurs at the polymer film/mucin solution interface.