Silicone biomaterials obtained by plasma treatment and subsequent surface hydrosilylation

Abstract: The need for safe and functional implants has led to anincreased demand for improved biomaterials. The performance invivo depends on the interaction between the biologicalsurrounding and the surface of the material. By tailoring thesurface of a material with suitable bulk properties,biomaterials with an ability to interact with the biologicalsystem in a specific and controlled way are obtained. Siliconeelastomers have been used as biomaterials for several decades,but it is widely recognized that they are difficult to modifyby the conventional methods used for organic polymers due tothe partly inorganic structure of silicone.This thesis presents a strategy to obtain siliconebiomaterials by covalent coupling of molecules to the surfaceusing silicon chemistry. The first step is to introduce Si-Hgroups onto the surface of silicone elastomers by plasmatreatment. The second step is to react a terminal double bondof a molecule with the formed Si-H group by a catalyzedhydrosilylation reaction. The coupled molecule may eitherprovide the desired properties itself, or have a functionalitythat is able to couple another molecule with suitablecharacteristics.The influence of plasma treatment in hydrogen, argon andoxygen on the silicone elastomer was characterized by X-rayphotoelectron spectroscopy (XPS). To quantify the effect ofplasma treatment, the method of ternary XPS diagrams wasdeveloped. It was found that undesired silica-like layers wereformed under severe treatment conditions. Argon plasma at lowpower and short treatment time was the most suitable parametersetting. Subsequent hydrosilylation grafting ofallyltetrafluoroethylether, aminopropylvinylether andN-vinylformamide showed that it was possible to functionalizethe surface via a covalent link to the surface. The primaryamino groups introduced onto the surface were accessible forfurther coupling reactions. Heparin surfaces were obtained by acoupling reaction with the introduced amino groups.Keywords:Silicone elastomers, PDMS, XPS, ESCA, surfacemodification, plasma