Sulfation and preliminary biological evaluation of ethylene-vinyl alcohol copolymers

In order to obtain polymers provided with improved haemocompatibility a commercial ethylene-vinyl alcohol copolymer (EVAL) was chemically modified by introduction of different amounts of sulfate groups. The sulfation reaction was carried out by the reaction of hydroxy groups with two different sulfating reagents (ClSO3H and PySO3). The influence of the molar ratio of the reagents and the reaction time on the functionalization degree was evaluated also for elevated substitution degrees. No difference in the sulfation agents efficiency was noted. The new terpolymers (EVAL-SO3H) have been characterized by chemical and physio-chemical techniques as: titration of the acidic groups, Fourier Transform IR reflectance spectroscopy (FTIR-ATR), differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS) and H-1-NMR. The haemocompatibility was evaluated by in vitro plasma coagulation (APTT) and platelet aggregation tests and is proved to be excellent for sulfation degrees higher than 35% of the hydroxy groups of the polymer.