Abstract
Poly- and oligo(ethylene glycol)s are known to suppress the adsorption of biological material on surfaces. In this thesis is shown that when using these chains in either monolayers or polymeric architectures, fouling (undesired growth of biological material on surfaces) could be significantly reduced. First the synthesis of oligo(propylene glycol)s (OPG)
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is reported. Hybrids of oligo(ethylene glycol)s and oligo(propylene glycol)s were also prepared. The conformational properties of two (chiral) OEG/PG hybrids are assessed with 1H-NMR, spectral simulations and ab initio calculations. Monolayers of alkyl end-functionalised oligo(ethylene glycol)/oligo(propylene glycol) hybrids on either Si(100) (CAMs) or Au(111) SAMs were used as model surfaces to gain insight into the protein resistivity mechanism of the OEG chains. All monolayers were characterised by IR, static contact angle measurements, ellipsometry and protein resistivity studies. The CAMs did not show the same level of protein resistivity as comparable monolayers on Au (111). The SAMs on Au (111) neither adsorb fibrinogen or lysozyme. This is tentatively attributed to differences in intermolecular packing density of the respective monolayers, which for the CAMs is dependant on the preparation procedure. The packing density of CAMs is decisively lower than that of the corresponding SAMs. For the SAMs also a effect of chirality is observed. The synthesis of typical oligo(ethylene glycol) functionalised copolymethacrylates is then presented. Both random and block copolymers were synthesised, using free radical polymerisation techniques. The block copolymers were obtained by making use of the reversible addition-fragmentation transfer (RAFT) polymerisation method using cumyl dithiobenzoate. The copolymers were characterised using of 1H- and 13C-NMR spectroscopy, size-exclusion chromatography (SEC), Differential Scanning Calorimetry (DSC) and IR spectroscopy. The assembly behaviour of a block copolymer in aqueous solution was investigated using a fluorescence probe technique, light scattering and cryo-TEM experiments. After deposition of the random and block copolymers on either hydrophilic or hydrophobic Si (100) surfaces, their surface topology and morphology was studied using tapping-mode AFM. Biofilm formation on the copolymers was studied by following the growth of bacteria and diatoms and the production of (EPS) in time using CLSM. The results demonstrated that the coatings suppress deposition of the amount of biological material by almost 60%. Especially the block copolymer was found to possess the best antifouling properties; as a consequence of its assembly behaviour. It is concluded that the random and block copolymers of proper composition represent viable binder materials for the preparation of new benign anti-fouling coating systems. The adhesive properties of some typical oligo(ethylene glycol) containing polymethacrylates on a commercial primer (SigmaPrime) deposited on a steel substrate were evaluated for their use in long-term antifouling studies. It was found that the random copolymers adhered well to the SigmaPrime. The block copolymer gave a free-standing film during exposure to water. The ultimate test, application of our polymer materials on a ship’s hull, is still a future prospect, but the concept proved to be valuable as an alternative for the banned tributyl tin containing coating.
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