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As some proteins are known to interact with sulfated and phosphated biomolecules such as specific glycosaminoglycans, this study derives from the hypothesis that sulfonate and phosphonate groups on solid polymer surfaces might cause specific interfacial interactions. Such surfaces were prepared by plasma polymerization of heptylamine (HA) and subsequent grafting of sulfonate or phosphonate groups via Michael-type addition of vinylic compounds. Adsorption of the proteins fibrinogen, albumin (HSA) and lysozyme on these functionalised plasma polymer surfaces was studied by XPS and quartz crystal microbalance with dissipation (QCM-D). It was also studied whether pre-adsorption with HSA would lead to a passivated surface against further adsorption of other proteins. XPS confirmed grafting of vinyl sulfonate and vinyl phosphonate onto the amine surface and showed that the proteins adsorbed to saturation at between 1 and 2 h. QCM-D showed rapid and irreversible adsorption of albumin on all three surfaces, while lysozyme could be desorbed with PBS to substantial extents from the sulfonated and phosphonated surfaces but not from the amine surface. Fibrinogen showed rapid initial adsorption followed by slower additional mass gain over hours. Passivation with albumin led to small and largely reversible subsequent adsorption of lysozyme, whereas with fibrinogen partial displacement yielded a mixed layer, regardless of the surface chemistry. Thus, protein adsorption onto these sulfonated and phosphonated surfaces is complex, and not dominated by electrostatic charge effects. Refereed/Peer-reviewed

In this report, we demonstrate that continuous improvement in XPS instruments and the calibration standards as well as analysis with standard component-fitting procedures can be used to determine the binding energies of compounds containing phosphorus and sulfur of different oxidation states with higher confidence. Based on such improved XPS analyses, the binding energies (BEs) of S2p signals for sulfur of increasing oxidation state are determined to be 166-167.5 eV for S=O in dimethyl sulfoxide, 168.1 eV for S=O2 in polysulfone, 168.4 eV for SO3 in polystyrene sulfonate and 168.8 eV for SO4 in chondroitin sulfate. The BEs of P2p signals show the following values: 132.9 eV for PO3 in triisopropyl phosphite, 133.3 eV for PO4 in glycerol phosphate, 133.5 eV for PO4 in sodium tripolyphosphate and 134.0 eV for PO4 in sodium hexametaphosphate. These results showed that there are only small increases in the binding energy when additional oxygen atoms are added to the S-O chemical group. A similar result is obtained when the fourth oxygen or poly-phosphate environment is added to the phosphorus compound. These BE values are useful to researchers involved in identifying oxidation states of phosphorus and sulfur atoms commonly observed on modified surfaces and interfaces found in applications such as biomaterials, super-capacitors and catalysis Refereed/Peer-reviewed

In comparison with other chemistries, little has been reported on sulfur-containing plasma polymers; reasons include low volatility or high toxicity of monomers. Here, we report on plasma polymerization of dimethyl sulfoxide, by itself and its co-polymerization with 1,7-octadiene to generate S-containing plasma polymers. Results show dominance of S-S, S-H, and S-C with small percentages of SO and SO2. Upon storage in air there were no observable changes to the oxidation states of the S atoms in these plasma polymers, whereas the hydrocarbon component underwent oxidative changes. Methods were studied to oxidize the initial sulfur-containing surface groups, but approaches such as H2O2 treatment post-deposition and electrical biasing during deposition did not affect the oxidation states of the incorporated S. Refereed/Peer-reviewed

Novel polyethyleneimine–phosphonate–carboxylic copolymers with an increasing number of carboxyl-ate and phosphonate groups have been synthesised. The presence of positively charged amino groups andnegatively charged carboxylate and phosphonate groups influenced the adsorption of these copolymerson boehmite colloidal particles and their dispersant ability in solution at pH values below and abovethe isoelectric point (iep) of boehmite. It was found that the addition of negatively charged carboxylategroups to the polyethyleneimine polymer backbone had a positive effect on polymer adsorption densityand affinity for the boehmite surface while the phosphonate groups had a negative effect. The adsorptionof these copolymers on the boehmite surface is largely controlled by electrostatic attractions with thepositively and negatively charged aluminium sites below and above the iep of boehmite, respectively. Thechanges in yield stress of the boehmite particle suspension following copolymer adsorption are largelyexplained by electrical double layer interaction between the boehmite particles, but also by van der Waalsor steric interactions between the polymer-coated particles. Refereed/Peer-reviewed

Phosphate groups are part of biological molecules involved in bio-interfacial phenomena but monomers containing these groups are not volatile enough to be plasma polymerized(pp). Hence monomers with lower oxidation states of P are needed which then does not enable prediction of the oxidation state(s) of P in the pps, nor of possible aging effects. XPS and FTIR analyses of pps from triisopropyl phosphite (TIP) and diethyl phosphite (DEP) reveal the presence of phosphate and polyphosphate groups, while phosphonate and phosphate are found in pps of copolymerized1,7-octadiene and TIP. Post-plasma aging and electrical biasing have negligible effects on the oxidation state of P in TIP pps. Refereed/Peer-reviewed

Addition of ionized terminal groups to PEG graft layers may cause additional interfacial forces to modulate the net interfacial interactions between PEG graft layers and proteins. In this study we investigated the effect of terminal sulfonate groups, characterizing PEG-aldehyde (PEG-CHO) and sulfonated PEG (PEG-SO3) graft layers by XPS and colloid probe AFM interaction force measurements as a function of ionic strength, in order to determine surface forces relevant to protein resistance and models of bio-interfacial interaction of such graft coatings. On the PEG-CHO surface the measured interaction force does not alter with ionic strength, typical of a repulsive steric barrier coating. An analogous repulsive interaction force of steric origin was also observed on the PEG-SO3 graft coating; however, the net interaction force changed with ionic strength. Interaction forces were modelled by steric and electrical double layer interaction theories, with fitting to a scaling theory model enabling determination of the spacing and stretching of the grafted chains. Albumin, fibrinogen, and lysozyme did not adsorb on the PEG-CHO coating, whereas the PEG graft with terminal sulfonate groups showed substantial adsorption of albumin but not fibrinogen or lysozyme from 0.15 M salt solutions. Under lower ionic strength conditions albumin adsorption was again minimized as a result of the increased electrical double-layer interaction observed with the PEG-SO3 modified surface. This unique and unexpected adsorption behaviour of albumin provides an alternative explanation to the "negative cilia" model used by others to rationalize observed thromboresistance on PEG-sulfonate coatings. Refereed/Peer-reviewed

Thesis (PhD)--University of South Australia, 2010 The aim of this research was to investigate the structural and chemical properties of dispersants and thereby identify a potential replacement for the phosphate dispersants in the titania pigment industry. Phosphonate copolymers which have improved thermal stability across a broad range of pH values have the potential to be used as dispersants in the titania pigment manufacturing process. The specific aims of this research were firstly to synthesize and characterise copolymers containing phosphonate and carboxylate functional groups with different phosphonate to carboxylate ratios, secondly to investigate their interaction with boehmite particles, used as model of the titania pigment surface, and thirdly to study their ability in dispersing boehmite suspensions as a function of pH and polymer concentration.

The preparation of thin film coatings with sulfonate and sulfate groups by plasma techniques is not straightforward due to limited volatility of suitable process vapours. We report a combination of plasma polymerisation and plasma treatment, treating heptylamine (HA-SO2) and 1, 7-octadiene (OD-SO2) plasma polymers with sulfur dioxide plasma. HA-SO 2 and OD-SO2 plasma polymer surfaces exhibited different compositions with the latter showing almost twice the amount of sulfur, as well as polysulfonate. Ageing of HA-SO2 plasma polymer surfaces in air or saline solution led to the disappearance of oligomers containing sulfonate and sulfate. Angle-dependent XPS analysis of HA-SO2 plasma polymers suggested that sulfur containing groups reptated into the plasma polymer upon storage after preparation. Refereed/Peer-reviewed

Chemical functionalisation of polymeric scaffolds with functional groups such as amine could provide optimal conditions for loading of signalling biomolecules over the entire volume of the porous scaffolds. Three-dimensional (both surface and bulk) functionlisation of large volume scaffolds is highly desirable, but preferably without any change to the basic morphological, structural and bulk chemical properties of the scaffolds. In this work, we have carried out and compared treatments of poly(lactide-co-glycolide) tissue engineering scaffolds by two methods, that is, a wet chemical method using ethylenediamine and a glow discharge plasma method using heptylamine as a precursor. The samples thus prepared were analysed by scanning electron microscopy and X-ray photoelectron spectroscopy. The plasma treatment generated amide and protonated amine (NH + ) groups which were present in the bulk and on the surface of the scaffold. Amination also occurred for the wet chemical treatments but the structural and chemical integrity were adversely affected.

Refereed/Peer-reviewed

This paper describes three methods for producing sulfated and phosphated surfaces using plasma-based technologies, namely plasma treatment, plasma polymerization, and plasma activation followed by chemical grafting. Plasma treatment using sulfur dioxide (SO2) produced sulfur-containing groups while plasma polymerization using triisopropyl phosphite (TIP) as the monomer created phosphated surfaces. The plasma-plus-grafting technique involved deposition of an amine plasma polymer followed by grafting with vinyl sulfonate or vinyl phosphonic acid via Michael addition. The various oxidation states and surface charges of chemical groups present on the surfaces were assessed by the surface analytical techniques X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). The stability and ageing mechanism of these plasma surfaces were also characterized.

Brominated furanones have attracted recent interest as antibacterial compounds. To utilize them as protective coatings in biomedical device applications, they must be covalently immobilized onto solid surfaces; however, interfacial coupling protocols developed for other biomolecules are not applicable to furanones. An azide reaction scheme has enabled covalent immobilization onto fluorinated ethylene propylene copolymer but its chemistry is less predictable, requiring detailed characterization by XPS and tapping mode AFM after each step of the immobilization sequence. XPS curve fitting resolved components in the C 1s, N 1s and Br 3d regions. Angle dependent XPS was used to assess the depth distributions and layer thicknesses. The results indicated successful covalent immobilization of furanones; however, side reactions occurred. In addition to the expected C Br, a contribution from bromine ion (Br − ) was detected, indicating that photo-degradation of furanones took place during UV illumination, and this reaction was found to increase with illumination time. The Br − was removed by washing with water, whereas the C Br signal from immobilized furanone remained. Spectroscopic characterization will assist in elucidating the structure of furanone coatings, understanding their mode of action when covalently immobilized on surfaces, and rationally designing and optimizing an effective antibacterial coating for biomedical applications.

Silica supported metallocene catalysts were prepared for ethylene polymerization by immobilizing bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) onto both calcined silica, and silica treated with γ-aminopropyltrimethoxysilane or γ-mercaptopropyltrimethoxy-silane. Bis(cyclopentadienyl)zirconium chloride hydride (Cp2ZrClH) was also immobilized onto both calcined silica and vinyltrimethoxysilane treated silica. The catalysts were characterized by using direct current plasma atomic emission spectroscopy (DCP-AES), diffuse reflectance infrared spectroscopy (DRIFT), and X-ray photoelecton spectroscopy (XPS). It was found that both Cp2ZrCl2 and Cp2ZrClH were adsorbed on both calcined silica and silane treated silica, respectively. When γ-aminopropyltrimethoxysilane (APTMS) was used as the spacer molecule, some of the amine became protonated upon adsorption of Cp2ZrCl2. Initial catalytic tests showed that all of the complexes were catalytically active (methylaluminoxane as a cocatalyst), with the Cp2ZrClH su...