The surface chemistry of polymeric bioseparation materials

Abstract

The aim of this thesis was to test existing theories concerning biocompatibility of polymeric materials, and in the process to try and identify the major factors which pertain to their use as bioseparation matrices. The surface chemistry of cellulose and poly(tetrafluoroethyIene) based bioseparation materials have been examined. We have been able to demonstrate a direct link in the case of the cellulose materials between the crystallinity and the accessibility of the hydroxyl groups which are the primary sites of functionalization. In addition, the effect of processing conditions on the pore structure of an amorphous cellulose matrix was demonstrated and this has been shown to have a direct consequence for the protein binding characteristics of the material. The functionalisation of PTFE has been achieved by reaction with sodium naphthalenide, which lead to the defluorination of the PTFE surface and the formation of a unsaturated carbonised layer containing oxygenated functionalities. The reaction has also been shown to alter the morphology of PTFE membranes as evidenced by AFM analysis. In the case of powdered PTFE we observed the formation of a microporous layer, however this was found to revert back to a fluorinated layer with gentle heating. A novel insight in to the defluorination reaction was obtained using the bombardment of PTFE and PVDF with a Na atom beam under ultra-high vacuum conditions. This demonstrated the single valence electron mechanism of the reaction and also showed the formation of NaF at the surface of the polymer. The formation of CF(_3) groups was attributed to the nucleophilic attack of fluoride ions from molecular NaF species formed at the initial stages of the reaction.