No description available.

This thesis is concerned with the synthesis of diazo compounds for the introduction of various functional groups on the surface of polymers by means of carbene insertion and diazonium coupling. Characterisation and investigation of their properties were conducted. A library of functionalised polystyrene beads containing pyridine rings has been established for the coordination of metal ions and metal complexes. The pyridyl system on the surface has demonstrated its capability to bind with zinc complexes of bis(thiosemicarbazones) and release the corresponding copper complexes upon transmetallation. A spiropyran derivative has been introduced onto the surface of polystyrene and polyethylene terephthalate. The chromophore on both polymers exhibited photoswitchability as determined from colour change and wettability. Polystyrenes with either pyridine or spiropyran units have been investigated for reversible immobilisation of bioactive species. Materials coated with penicillin V gave significant inhibition zones in antibacterial assays, showing efficacy in drug delivery. Finally, a range of diazo compounds with different substituents has been synthesised and their thermal stabilities have been assessed by differential scanning calorimetry technique.

Patch clamping is considered the gold standard in measuring the bioelectrical activity of a cell. It is used to detect and measure ion transport through ion channels located throughout a cell membrane. Ion movement is crucial to cell viability and cell-to-cell communication. Pharmaceutical companies increasingly target ion channels because of their significance in disease and to help design better targeted drugs. However, the traditional method of patch clamping is cumbersome and is being replaced by planar high throughput screening (HTS) systems. These systems are reaching their limits due to materials and cost of processing; cell handling methods and small varieties of applicable cell types are also issues to be addressed. In this work, the core components of a new kind of planar patch clamping device have been designed and developed, after analysis of currently available HTS systems. This design approaches patch clamping using polymers to overcome some of the limitations in current systems, specifically cell handling and positioning, by using a simple modification technique to provide distinct attractive areas for cell binding. This uniquely allows the culture of both single cells and cell networks to increase the range of cell types that can be measured and circumvents challenges from using suction to pull cells onto measurement holes. The components of the design are a 10 x 10 array of small holes drilled in a polymer then aligned modifications for precise cell placement are added and a planar electrode array for individual addressing of each cell. A study of methods to produce a leak-tight seal required between microfluidic chambers was done. Cell adhesion parameters for the modification techniques were established. The principle viability of this approach was confirmed using the modification technique to culture cells over holes and measure their resistance using a rig developed for this work.

To create functional surfaces for soft materials, such as polyurethanes, our approach is to use a semifluorinated surface modifier as minor component to the matrix material. The surface modifier, driving by reduction in surface energy, surface-concentrates to form a functionalized surface layer at the air-polymer interface. In our previous studies, linear PTMO-based polyurethanes were used as the matrix material. These systems undergo slow surface phase separation at room temperature due to the thermodynamically immiscibility of the soft blocks. In this study, chemically crosslinked matrix was developed to provides a steric hindrance to constrain the mobility of surface modifier and to form a kinetically stable surface. The physical property and morphology of base crosslinked matrix has been characterized using DSC, UTT, DMA and AFM. The surface morphology of surface modified crosslinked matrix has been characterized using AFM, DCA and XPS.

This thesis investigates the application of plasma immersion ion implantation (PIII) to polymers. PIII requires that a high negative potential be applied to the surface of the material while it is immersed in a plasma. This presents a problem for insulating materials such as polymers, since the implanting ions carry charge to the surface, resulting in a charge accumulation that effectively neutralises the applied potential. This causes the plasma sheath at the surface to collapse a short time after the potential is applied. Measurements of the sheath dynamics, including the collapsing sheath, are performed using an electric probe. The results are compared to theoretical models of the plasma sheath based on the Child-Langmuir law for high voltage sheaths. The theoretical model predicts well the sheath dynamics for conductive substrates. For insulating substrates the model can account for the experimental observations if the secondary electron coefficient is modified, justified on the basis of the poly-energetic nature of the implanting ions. If a conductive film is applied to the insulator surface the problem of charge accumulation can be avoided without compromising the effectiveness of PIII. The requirement for the film is that it be conductive, yet transparent to the incident ions. Experimental results are presented which confirm the effectiveness of the method. Theoretical estimates of the surface potential show that a film of the order of 5nm thickness can effectively circumvent the charge accumulation problem. Efforts to produce and characterise such a film form the final two chapters of this thesis. The optimal thickness is determined to be near the percolation threshold, where a marked increase in conductivity occurs. Spectroscopic ellipsometry is shown to be an excellent method to determine the film thickness and percolation threshold non-invasively. Throughout this work cathodic vacuum arcs are used to deposit thin films and as a source of metal plasmas. The design and construction of a pulsed cathodic vacuum arc forms a significant part of this thesis. Investigations of the cathode spots and power supply requirements are presented.

This thesis investigates the application of plasma immersion ion implantation (PIII) to polymers. PIII requires that a high negative potential be applied to the surface of the material while it is immersed in a plasma. This presents a problem for insulating materials such as polymers, since the implanting ions carry charge to the surface, resulting in a charge accumulation that effectively neutralises the applied potential. This causes the plasma sheath at the surface to collapse a short time after the potential is applied. Measurements of the sheath dynamics, including the collapsing sheath, are performed using an electric probe. The results are compared to theoretical models of the plasma sheath based on the Child-Langmuir law for high voltage sheaths. The theoretical model predicts well the sheath dynamics for conductive substrates. For insulating substrates the model can account for the experimental observations if the secondary electron coefficient is modified, justified on the basis of the poly-energetic nature of the implanting ions. If a conductive film is applied to the insulator surface the problem of charge accumulation can be avoided without compromising the effectiveness of PIII. The requirement for the film is that it be conductive, yet transparent to the incident ions. Experimental results are presented which confirm the effectiveness of the method. Theoretical estimates of the surface potential show that a film of the order of 5nm thickness can effectively circumvent the charge accumulation problem. Efforts to produce and characterise such a film form the final two chapters of this thesis. The optimal thickness is determined to be near the percolation threshold, where a marked increase in conductivity occurs. Spectroscopic ellipsometry is shown to be an excellent method to determine the film thickness and percolation threshold non-invasively. Throughout this work cathodic vacuum arcs are used to deposit thin films and as a source of metal plasmas. The design and construction of a pulsed cathodic vacuum arc forms a significant part of this thesis. Investigations of the cathode spots and power supply requirements are presented.

Contact antimicrobial coatings with poly-alkylammonium compositions have been a subject of increasing interest in part because of the contribution of biocide release coatings to antibiotic resistance. Herein, a concept for antimicrobial coatings is developed based on thermodynamically driven surface concentration of soft block side chains. The concept incorporates structural and compositional guidance from naturally occurring antimicrobial proteins and achieves compositional economy via a polymer surface modifier (PSM). For this purpose, polyurethanes having P[AB] co-polyoxetane soft blocks, where A is a surface active (fluorous) or PEG-like side chain and B represents a desired function (alkylammonium) were prepared. Specifically, poly(2,2-substituted-1,3-propylene oxide) ran-co-telechelics with bromobutoxymethyl (CH2O(CH2)4Br) and either trifluoroethoxymethyl (3FOx, -CH2OCH2CF3)) or PEG-like (2-(2-methoxyethoxy)ethoxy)methyl (ME2Ox, (-CH2(OCH2CH2) 2OCH3)) side chains were prepared via cationic ring opening polymerization. Characterization utilized 1H NMR spectroscopy, temperature modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA). Molecular weights (Mn) by 1H NMR end group analysis were ~6000-8000g/mole. Bromobutoxymethyl groups were completely substituted with N,N-dimethylalkyl amines to obtain alkylammonium co-telechelics. Two alkyl ammonium chain lengths, six carbons (C6) and twelve carbons (C12) were used. Tgs of bromobutoxymethyl co-telechelics were -68 degrees C and -48 degrees C for ME2Ox and 3FOx, respectively. Tgs remained low after amine substitution. Alkylammonium co-telechelics decomposed at 220-230 degrees C regenerating amine. Telechelics were incorporated into polyurethanes (PUs) having 4,4'-(methylene bis (p-cyclohexyl isocyanate) (H12MDI) and butanediol (BD) as the hard block (30wt%). Characterization by 1H NMR, GPC, MDSC and TGA is described. From DSC data, using the Fox equation, the weight fraction of pure soft block in the soft block domain (w1) was very high (0.96-0.99) for polyurethanes with fluorous soft blocks, while soft blocks with PEG-like side chains were phase mixed (w1 = 0.73-0.75). To our knowledge, this is the first time that a polycationic telechelic has been incorporated into a polyurethane. By using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR) spectroscopy, dynamic contact angle (DCA) analysis, sessile drop measurement, and Tapping Mode Atomic Force Microscopy (TM-AFM), surface properties of polyurethanes were examined. These polyurethanes were co-processed with base polyurethanes to modify surfaces. Surface concentration of 2 wt % P[AB]-polyurethanes was studied by using the same surface characterization methods. Surface concentration of semifluorinated and alkylammonium side chains (C6 and C12) was observed. Miscibility of PEG-like side chains resulted in weak concentration of short alkyl ammonium side chains (C6). However, longer alkylammonium side chains (C12) can 'self-chaperone' and surface concentrate better compared to shorter side chain analogs. For biocidal testing, aerosol and touch tests were designed and implemented. Coatings were tested for zone of inhibition. The polyurethanes were first tested as 100 wt % coatings and found to be highly effective against both Gram(-) (Pseudomonas aeruginosa, Escherichia coli) and Gram(+) (Staphylococcus aureus) bacteria. Polyurethane modified surfaces (2 wt %) were tested against aerosol challenges of the same bacteria strains. The 2 wt % PSM with soft block containing trifluoroethoxy (A, 89 mol %) and C12 alkylammonium (B, 11mol %) side chains gave the highest biocidal effectiveness against all bacteria strains in 30 min (100% kill, 3.6-4.4 log reduction).

The thesis is devoted to the development of general methods of preparation of tethered polymer layers with laterally changing properties and investigation of their properties with focus on controlled adsorption and liquid flow. The temperature dependent character of the grafting reaction is used for the design of mono- and bicomponent gradient polymer grafted layers. For this purpose, a special stage providing a lateral temperature gradient is designed. The stage consists of two elements, one heating and one cooling, between which the experimental sample is situated. The versatility of these approaches for both fundamental research and practical applications is demonstrated. In general, the gradient approach is proved to be useful for the combinatorial-like investigations of ultrathin polymer films. The systematic study allowed detailed investigation of the grafting kinetics, the morphologies of the grafted polymer layers, the switching mechanism of the mixed polymer brushes, adsorption of colloid particles. The second approach for the preparation of laterally resolved tethered layers consists of a novel strategy for reversible environment-responsive lithography. This strategy implies local fixation of the morphology of mixed polymer brushes via photocrosslinking by UV irradiation. Irradiated areas lose the ability to switch. Exposure to selective and non-selective solvent allows visualization or erasing of the written information, respectively. It is demonstrated that developed approaches are promising for design of smart sensors, microfluidics devices, combinatorial study of the adsorption (separation and identification) of protein molecules and colloids and for other applications.

The purpose of this research was to identify the types of surface treatments available for use on concrete bridge decks and to determine which materials are most capable of providing long-term protection from contamination by chloride ions. The products addressed in this report primarily include urethanes, silicon-based sealers, and epoxies. An extensive literature review was conducted to document common overlay distresses, performance histories, and properties of specific surface treatment products currently available in the industry. In addition, three reports summarizing in-house experiments performed by the Utah Department of Transportation between 1995 and 2003 regarding various types of surface treatments were reviewed as part of this research. Finally, a nationwide questionnaire survey was conducted to investigate the state-of-the-practice with regard to surface treatment applications on bridge decks by state departments of transportation throughout the United States. Of the three types of materials addressed in this research, epoxy-based products have the greatest ability to protect concrete and remain uncracked with an acceptable level of skid resistance. Silicon-based products do not crack because they seep into the pores of the concrete, but they do not protect the concrete from the wearing effects of traffic or improve skid resistance. Published field studies indicate that urethane surface treatments do not resist the effects of traffic as well as epoxy-based materials, nor do they offer a substantial decrease in expense or health risk when compared to epoxy-based products. The results of the nationwide questionnaire clearly indicate that bridge deck surface treatments are valuable as both chloride barriers and skid-resistant wearing courses. No standard practice appears to exist with regard to timing of surface treatments, however. Some states arbitrarily apply surface treatments at 10 to 12 years after construction, other states wait until cracking has become fairly considerable before action is taken, and still other states apply surface treatments when the chloride content of the concrete reaches a certain level. Because concrete decks with significant cracking are not ideal substrates for polymer applications, surface treatments should be applied as preventive measures early in the service lives of bridge decks to effectively prevent chloride concentrations from reaching critical levels. This research suggests that epoxy-based surface treatments should be specified for concrete bridge decks when both a chloride barrier and improved skid resistance are desired. If a chloride barrier is all that is needed or desired, a silane surface treatment should be considered; silane treatments are less expensive and easier to apply than epoxy treatments. When a large amount of epoxy is to be mixed, automatic proportioning equipment that can precisely monitor and control the ratios of components should be employed.

No description available.