Plasma polymerisation: study and application

Abstract

Molecular interactions are often studied using immobilised organic and biological entities at the surface of a substrate. Functionalisation of such surfaces can be achieved via different technologies such as Langmuir-Blodgett films, self-assembled monolayers and spin-coated layers. The main drawback of these methods is the dependence on the substrate, limiting the scope of possible applications. Conversely, plasma polymerisation entails the deposition of thin polymeric films at the surface of a wide variety of substrates. The development of pulsed plasma has opened new paths allowing the high controllability of the functionality and the thickness of the deposited layer. This thesis describes the functionalisation of a surface with pentafluorophenyl ester in a one-step process, reaching higher immobilization yield of bio-molecules than in a multi-step process. Also, the nature of pulsed-plasma polymers provides additional benefits such as irregular surfaces which make functionalities more accessible for subsequent reactions such as enzymatic modification as investigated in the fourth chapter. Finally, the last two chapters of this thesis deal with the occurrence of trapped free radicals within plasma polymers and their ability to induce graft-polymerisation of polymer brushes without prior attachment of initiators at the surface of a substrate. A comparison is drawn between a 'conventional' method using an initiator immobilised on the surface and trapped radicals to induce graft polymerisation. The influence of he nature of the monomer used during plasma polymerisation along with the conditions of deposition are studied with respect to the rate of subsequent graft polymerisation of styrene and the amount of trapped free radicals.