Radiation Induced Modification of Polyetherurethane Tubes with Hema and Acrylamide

Abstract

In a previous work we described the modification of polyetherurethane films with hydrophilic monomers via radiation grafting in order to improve the thromboresistance of the polymer surface.^1,2 Following the “preswelling technique”, the trunk polymer films were swollen with monomer (2-hydroxyethyl methacrylate, 2,3-dihydroxypropyl methacrylate, acrylamide) for certain lengths of time and irradiated afterwards in the absence of surrounding monomer. Using this method, graft copolymers with different penetration depths of the graft component in the trunk polymer could be obtained, leading to different surface properties of the grafted films. The investigation of the mechanical behaviour of the grafted products showed that mechanical strength decreases with increasing grafting yield, but that low grafted films (grafting yield < 5%) nearly have the same mechanical properties as the trunk polymer.³ Furthermore in this study it was tried to correlate surface parameters as contact angle and interfacial free energy γ _sw between polymer and water with the results of protein adsorption to the film surfaces.^2,3 found that for grafted films with a grafting yield below 5% the protein adsorption decreases as the interfacial free energy ysw decreases, as it was postulated by J.D. AN- DRADE in his “minimum interfacial free energy hypothesis”. ⁴ Films with higher grafting yields do not follow this hypothesis, due to an increase in surface area caused by the grafting process. These high grafted samples preferentially do adsorb albumin, the extent of the albumin adsorption being a function of the grafting yield. Recent results of platelet adhesion measurements as performed with the SPFE (Stagnation Point Flow Experiment) -test⁵ revealed, that platelets have a low tendency to adhere to HEMA grafted polyetherurethane films with low grafting yield and low interfacial free energy.⁶