Polyphosphazenes as biomaterials: surface modification of poly(bis(trifluoroethoxy)phosphazene) with polyethylene glycols.

Investigations were carried out on the metathetical exchange reaction between the -O-CH2CF3 moieties of poly(bis(trifluoroethoxy)phosphazene) (PTFP), in the state of slightly swollen films, and the alkoxide ions derived from methoxypolyethylene glycol (MPEG) of molecular mass ranging from 350 to 5000 g/mol. The substitution of these hydrophilic chains, mostly confined to thin surface layers, was revealed by means of optical microscopy and scanning electron microscopy observations, surface elemental analysis by energy-dispersive X-ray analysis (EDXA), FTIR-ATR analysis and water contact angle measurements. The surface biocompatibility was enhanced in all cases, whilst the mechanical properties of the original PTFP films were substantially retained in the modified samples exhibiting low substitutions. Such samples were obtained especially when the metathetical reaction was carried out with MPEG5000.