Improvement of swelling properties of PHEMA hydrogel by means of the biomimetic method

Structurally modified PHEMA, by means of polymer blends and random copolymers, are intensively studied in order to improve the mechanical properties. Recently it was shown that an hydroxyapatite coating, that should improve the bone interaction of this biomaterial, can be obtain by means of the biomimetic method. In this paper it is shown that when PHEMA is submitted to the biomimetic method its swelling ratio is improved. This can be ascribed to the deposition, during the first stage of the method, on the surface of the internal pores, of a silicatic layer, that improves the hydrophilicity. This appears a valuable result in the view of producing modified PHEMA with improved mechanical properties and good swelling properties. The experimental results suggest and indicate the following:stronger interactions with the water molecules are set up; an induction period is observed linked to the rate of the reactions occurring at the surface of the glass and the establishment of a convenient concentration of the silicate ions at the external surface of the polymer, and the diffusion of the SBF into the pores is the limiting stage of the process.