Counter-ion effect on surfactant-DNA gel particles as controlled DNA delivery systems

The ability to entrap drugs within vehicles and subsequently release them has led to new treatments for a number of diseases. Based on an associative phase separation and interfacial diffusion approach, we developed a way to prepare DNA gel particles without adding any kind of cross-linker or organic solvent. Among the various agents studied, cationic surfactants offered particularly efficient control for encapsulation and DNA release from these DNA gel particles. The driving force for this strong association is the electrostatic interaction between the two components, as induced by the entropic increase due to the release of the respective counter-ions. However, little is known about the influence of the respective counter-ions on this surfactant-DNA interaction. Here we examined the effect of different counter-ions on the formation and properties of the DNA gel particles by mixing DNA (either single-(ssDNA) or double-stranded (dsDNA)) with the single chain surfactant dodecyltrimethylammonium (DTA). In particular, we used as counter-ions of this surfactant the hydrogen sulfate and trifluoromethane sulfonate anions and the two halides, chloride and bromide. Effects on the morphology of the particles obtained, the encapsulation of DNA and its release, as well as the haemocompatibility of these particles are presented, using counter-ion structure and DNA conformation as controlling parameters. Analysis of the data indicates that the degree of counter-ion dissociation from the surfactant micelles and the polar/hydrophobic character of the counter-ion are important parameters in the final properties of the particles. The stronger interaction with amphiphiles for ssDNA than for dsDNA suggests the important role of hydrophobic interactions in DNA.

Ion-Conducting Membranes Based on Gelatin and Containing LiI/I-2 for Electrochromic Devices

Ionic conducting membranes of gelatin plasticized with glycerol and containing LiI/I-2 have been obtained and characterized by X-ray diffraction measurements, UV-Vis-NIR spectroscopy, thermal analysis and impedance spectroscopy. The transparent (80-90% in the visible range) membranes showed ionic conductivity value of 5 x 10(-5) S/cm at room temperature, which increased to 3 x 10(-3) S/cm at 80 degrees C. All the ionic conductivity measurements as a function of temperature showed VTF dependence and activation energy of 8 kJ/mol. These samples also showed low glass transition temperature of -76 degrees C. Moreover the samples were predominantly amorphous. The membranes applied to small electrochromic devices showed 20% of color change from colored to bleached states during more than 70 cronoamperometric cycles.

Decay of imprinted surface waves in polymers

CONCLUSIONS The focus of this work was the investigation ofanomalies in Tg and dynamics at polymer surfaces. Thethermally induced decay of hot-embossed polymer gratings isstudied using laser-diffraction and atomic force microscopy(AFM). Monodisperse PMMA and PS are selected in the Mwranges of 4.2 to 65.0 kg/mol and 3.47 to 65.0 kg/mol,respectively. Two different modes of measurement were used:the one mode uses temperature ramps to obtain an estimate ofthe near-surface glass temperature, Tdec,0; the other modeinvestigates the dynamics at a constant temperature aboveTg. The temperature-ramp experiments reveal Tdec,0 valuesvery close to the Tg,bulk values, as determined bydifferential scanning calorimetry (DSC). The PMMA of65.0 kg/mol shows a decreased value of Tg, while the PS samples of 3.47 and 10.3 kg/mol (Mwion widthbetween the onset of an amplitude reduction and a finalstate is smaller in the case of PS than in the case of PMMA.This suggests a higher degree of cooperation between thepolymer chains for PMMA than for PS chains even near thesurface. A reduction of the investigated near-surface region byusing smaller grating constants and AFM did not show achange in the near-surface Tdec,0. Decay experiments were performed at a variety ofconstant temperatures. Master plots are produced by shifting the decay curves, on the logarithmic time scale,with respect to a reference curve at Tref. From thisprocedure shift factors were extracted. An Arrhenius analysis of the shift factors reveals adecreasing non-Arrhenius (fragile) behavior with molecular weight for PMMA. PS is fragile for all Mw asexpected for linear polymers. Non-Arrhenius behavior allowsone to fit the shift factors to the William-Landel-Ferry(WLF) equation. The WLF parameters for the varying molecular weights ofPMMA and PS were extracted and compared to the values frombulk rheology measurements. Assuming cg1=16+/-2 at Tg, assuggested by Angell, the glass temperature was determinedfrom the dynamic decay experiments. Within the experimentalerrors, the values for Tg,surf(c1=16) and T_g,bulk(c1=16)tend to be smaller than Tdec,0 and Tg,bulk fromtemperature-ramp and DSC measurements, but confirm thecourse of the values with increasing Mw. The comparison of the fragilities (temperaturedependence of the polymer properties at Tg) near the surfaceand in the bulk shows a higher fragility for PS near thesurface, a lower one for PMMA with molecular weights of 4.2and 65.0 kg/mol. The different surface behavior of PS istraced back to a lower degree of cooperation and a largerfree volume fraction.

Advanced lithium and lithium-ion rechargeable batteries for automotive applications

The worldwide demand for a clean and low-fuel-consuming transport promotes the development of safe, high energy and power electrochemical storage and conversion systems. Lithium-ion batteries (LIBs) are considered today the best technology for this application as demonstrated by the recent interest of automotive industry in hybrid (HEV) and electric vehicles (EV) based on LIBs. This thesis work, starting from the synthesis and characterization of electrode materials and the use of non-conventional electrolytes, demonstrates that LIBs with novel and safe electrolytes and electrode materials meet the targets of specific energy and power established by U.S.A. Department of Energy (DOE) for automotive application in HEV and EV. In chapter 2 is reported the origin of all chemicals used, the description of the instruments used for synthesis and chemical-physical characterizations, the electrodes preparation, the batteries configuration and the electrochemical characterization procedure of electrodes and batteries. Since the electrolyte is the main critical point of a battery, in particular in large- format modules, in chapter 3 we focused on the characterization of innovative and safe electrolytes based on ionic liquids (characterized by high boiling/decomposition points, thermal and electrochemical stability and appreciable conductivity) and mixtures of ionic liquid with conventional electrolyte. In chapter 4 is discussed the microwave accelerated sol–gel synthesis of the carbon- coated lithium iron phosphate (LiFePO 4 -C), an excellent cathode material for LIBs thanks to its intrinsic safety and tolerance to abusive conditions, which showed excellent electrochemical performance in terms of specific capacity and stability. In chapter 5 are presented the chemical-physical and electrochemical characterizations of graphite and titanium-based anode materials in different electrolytes. We also characterized a new anodic material, amorphous SnCo alloy, synthetized with a nanowire morphology that showed to strongly enhance the electrochemical stability of the material during galvanostatic full charge/discharge cycling. Finally, in chapter 6, are reported different types of batteries, assembled using the LiFePO 4 -C cathode material, different anode materials and electrolytes, characterized by deep galvanostatic charge/discharge cycles at different C-rates and by test procedures of the DOE protocol for evaluating pulse power capability and available energy. First, we tested a battery with the innovative cathode material LiFePO 4 -C and conventional graphite anode and carbonate-based electrolyte (EC DMC LiPF 6 1M) that demonstrated to surpass easily the target for power-assist HEV application. Given that the big concern of conventional lithium-ion batteries is the flammability of highly volatile organic carbonate- based electrolytes, we made safe batteries with electrolytes based on ionic liquid (IL). In order to use graphite anode in IL electrolyte we added to the IL 10% w/w of vinylene carbonate (VC) that produces a stable SEI (solid electrolyte interphase) and prevents the graphite exfoliation phenomenon. Then we assembled batteries with LiFePO 4 -C cathode, graphite anode and PYR 14 TFSI 0.4m LiTFSI with 10% w/w of VC that overcame the DOE targets for HEV application and were stable for over 275 cycles. We also assembled and characterized ―high safety‖ batteries with electrolytes based on pure IL, PYR 14 TFSI with 0.4m LiTFSI as lithium salt, and on mixture of this IL and standard electrolyte (PYR 14 TFSI 50% w/w and EC DMC LiPF 6 50% w/w), using titanium-based anodes (TiO 2 and Li 4 Ti 5 O 12 ) that are commonly considered safer than graphite in abusive conditions. The batteries bearing the pure ionic liquid did not satisfy the targets for HEV application, but the batteries with Li 4 Ti 5 O 12 anode and 50-50 mixture electrolyte were able to surpass the targets. We also assembled and characterized a lithium battery (with lithium metal anode) with a polymeric electrolyte based on poly-ethilenoxide (PEO 20 – LiCF 3 SO 3 +10%ZrO 2 ), which satisfied the targets for EV application and showed a very impressive cycling stability. In conclusion, we developed three lithium-ion batteries of different chemistries that demonstrated to be suitable for application in power-assist hybrid vehicles: graphite/EC DMC LiPF 6 /LiFePO 4 -C, graphite/PYR 14 TFSI 0.4m LiTFSI with 10% VC/LiFePO 4 -C and Li 4 T i5 O 12 /PYR 14 TFSI 50%-EC DMC LiPF 6 50%/LiFePO 4 -C. We also demonstrated that an all solid-state polymer lithium battery as Li/PEO 20 –LiCF 3 SO 3 +10%ZrO 2 /LiFePO 4 -C is suitable for application on electric vehicles. Furthermore we developed a promising anodic material alternative to the graphite, based on SnCo amorphous alloy.

A hybrid technology for parallel recording of single ion channels

Hybrid technologies, thanks to the convergence of integrated microelectronic devices and new class of microfluidic structures could open new perspectives to the way how nanoscale events are discovered, monitored and controlled. The key point of this thesis is to evaluate the impact of such an approach into applications of ion-channel High Throughput Screening (HTS)platforms. This approach offers promising opportunities for the development of new classes of sensitive, reliable and cheap sensors. There are numerous advantages of embedding microelectronic readout structures strictly coupled to sensing elements. On the one hand the signal-to-noise-ratio is increased as a result of scaling. On the other, the readout miniaturization allows organization of sensors into arrays, increasing the capability of the platform in terms of number of acquired data, as required in the HTS approach, to improve sensing accuracy and reliabiity. However, accurate interface design is required to establish efficient communication between ionic-based and electronic-based signals. The work made in this thesis will show a first example of a complete parallel readout system with single ion channel resolution, using a compact and scalable hybrid architecture suitable to be interfaced to large array of sensors, ensuring simultaneous signal recording and smart control of the signal-to-noise ratio and bandwidth trade off. More specifically, an array of microfluidic polymer structures, hosting artificial lipid bilayers blocks where single ion channel pores are embededed, is coupled with an array of ultra-low noise current amplifiers for signal amplification and data processing. As demonstrating working example, the platform was used to acquire ultra small currents derived by single non-covalent molecular binding between alpha-hemolysin pores and beta-cyclodextrin molecules in artificial lipid membranes.

Anhydrous proton conducting polymer electrolytes based on polymeric ionic liquids

Imidazolium types of ionic liquids were immobilized by tethering it to acrylate backbone. These imidazolium salt containing acrylate monomers were polymerize at 70oC by free radical polymerization to give polymers poly(AcIm-n) with n being the side chain lenght. The chemical structure of the polymer electrolytes obtained by the described synthetic routes was investigated by NMR-spectroscopy. The polymers were doped with various amounts of H3PO4 and LiN(SO2CF3)2, to obtain poly(AcIm-n) x H3PO4 and poly(AcIm-2-Li) x LiN(SO2CF3)2. The TG curves show that the polymer electrolytes are thermally stable up to about 200◦C. DSC results indicates the softening effect of the length of the spacers (n) as well as phosphoric acid. The proton conductivity of the samples increase with x and reaches to 10-2 Scm-1 at 120oC for both poly(AcIm-2)2H3PO4 and poly(AcIm-6)2H3PO4. It was observed that the lithium ion conductivity of the poly(AcIm-2-Li) x LiN(SO2CF3)2 increases with blends (x) up to certain composition and then leveled off independently from blend content. The conductivity reaches to about 10-5 S cm-1 at 30oC and 10-3 at 100oC for poly(AcIm-2-Li) x LiN(SO2CF3)2 where x is 10. The phosphate and phosphoric acid functionality in the resulting polymers, poly(AcIm-n) x H3PO4, undergoes condensation leading to the formation of cross-linked materials at elevated temperature which may improve the mechanical properties to be used as membrane materials in fuel cells. High resolution nuclear magnetic resonance (NMR) spectroscopy was used to obtain information about hydrogen bonding in solids. The low Tg enhances molecular mobility and this leads to better resolved resonances in both the backbone region and side chain region. The mobile and immobile protons can be distinguished by comparing 1H MAS and 1H-DQF NMR spectra. The interaction of the protons which may contribute to the conductivity is observed from the 2D double quantum correlation (DQC) spectra.

Liquid crystalline phases of anisotropic, polymer functionalized nanoparticles

Diese Arbeit beschäftigt sich mit der Polymerfunktionalisierung formanisotroperrnNanopartikel wie TiO2 Nanostäbchen oder Kohlenstoff Nanoröhren. Dies dient derrnSolubilisierung und sterischen Stabilisierung in organischen Medien, da diesernionenfrei hergestellt werden können, was eine Nutzung für nanoskopische,rnelektrische Schaltkreise ermöglicht. Die Polymere wurden mittels der RAFTrn(reversible addition-fragmentation chain transfer) Polymerisation mit engenrnMolekulargewichtsverteilungen hergestellt. Im Detail wurden Ankergruppen inrnBlockcopolymere und an der Alphaposition eingeführt, welche eine Anbindung an diernNanopartikeloberfläche ermöglichen. Die Polymere wurden durch Variation derrnverschiedenen Blocklängen für eine bestmögliche Adsorption optimiert. Die sorngewonnenen Polymer funktionalisierten Nanopartikel zeigten eine gute Löslichkeit inrnorganischen Medien und zeigten zudem eine lyotropes, flüssigkristallinesrnPhasenverhalten. Dies war aufgrund der Formanisotropie zu erwarten, zeigte jedochrnebenfalls ein unerwartetes thermotropes Verhalten, welches durch die Polymerhüllernerzeugt wurde. Die Flüssigkristalle wurden eingehend mittels polarisierterrnMikroskopie und Differential Scanning Calorimetry (DSC) untersucht. Diernflüssigkristallinen Phasen aus Nanostäbchen und –röhren wurde dann zurrnOrientierung der anisotropen Nanopartikel benutzt und es konnten makroskopischrngeordnete Proben hergestellt werden. Die Polymerhülle um die Nanopartikelrnermöglichte es ebenfalls diese in Polymerfilme einzuarbeiten und sornNanopartikelverstärkte Kunststoffe herzustellen.

Investigation of the lithium ion mobility in cyclic model compounds and their ion conducting properties

Efficient energy storage and conversion is playing a key role in overcoming the present and future challenges in energy supply. Batteries provide portable, electrochemical storage of green energy sources and potentially allow for a reduction of the dependence on fossil fuels, which is of great importance with respect to the issue of global warming. In view of both, energy density and energy drain, rechargeable lithium ion batteries outperform other present accumulator systems. However, despite great efforts over the last decades, the ideal electrolyte in terms of key characteristics such as capacity, cycle life, and most important reliable safety, has not yet been identified. rnrnSteps ahead in lithium ion battery technology require a fundamental understanding of lithium ion transport, salt association, and ion solvation within the electrolyte. Indeed, well-defined model compounds allow for systematic studies of molecular ion transport. Thus, in the present work, based on the concept of ‘immobilizing’ ion solvents, three main series with a cyclotriphosphazene (CTP), hexaphenylbenzene (HBP), and tetramethylcyclotetrasiloxane (TMS) scaffold were prepared. Lithium ion solvents, among others ethylene carbonate (EC), which has proven to fulfill together with pro-pylene carbonate safety and market concerns in commercial lithium ion batteries, were attached to the different cores via alkyl spacers of variable length.rnrnAll model compounds were fully characterized, pure and thermally stable up to at least 235 °C, covering the requested broad range of glass transition temperatures from -78.1 °C up to +6.2 °C. While the CTP models tend to rearrange at elevated temperatures over time, which questions the general stability of alkoxide related (poly)phosphazenes, both, the HPB and CTP based models show no evidence of core stacking. In particular the CTP derivatives represent good solvents for various lithium salts, exhibiting no significant differences in the ionic conductivity σ_dc and thus indicating comparable salt dissociation and rather independent motion of cations and ions.rnrnIn general, temperature-dependent bulk ionic conductivities investigated via impedance spectroscopy follow a William-Landel-Ferry (WLF) type behavior. Modifications of the alkyl spacer length were shown to influence ionic conductivities only in combination to changes in glass transition temperatures. Though the glass transition temperatures of the blends are low, their conductivities are only in the range of typical polymer electrolytes. The highest σ_dc obtained at ambient temperatures was 6.0 x 10-6 S•cm-1, strongly suggesting a rather tight coordination of the lithium ions to the solvating 2-oxo-1,3-dioxolane moieties, supported by the increased σ_dc values for the oligo(ethylene oxide) based analogues.rnrnFurther insights into the mechanism of lithium ion dynamics were derived from 7Li and 13C Solid- State NMR investigations. While localized ion motion was probed by i.e. 7Li spin-lattice relaxation measurements with apparent activation energies E_a of 20 to 40 kJ/mol, long-range macroscopic transport was monitored by Pulsed-Field Gradient (PFG) NMR, providing an E_a of 61 kJ/mol. The latter is in good agreement with the values determined from bulk conductivity data, indicating the major contribution of ion transport was only detected by PFG NMR. However, the μm-diffusion is rather slow, emphasizing the strong lithium coordination to the carbonyl oxygens, which hampers sufficient ion conductivities and suggests exploring ‘softer’ solvating moieties in future electrolytes.rn

Miniemulsionen als räumliche Begrenzungen : Synthese von Polymer-Hydroxylapatit-Nanopartikeln, bio-inspirierten Nanokapseln und Polymer-Einzelkettenpartikeln

In der vorliegenden Arbeit wurden Miniemulsionen als räumliche Begrenzungen für die Synthese von unterschiedlichen funktionellen Materialien mit neuartigen Eigenschaften verwendet. Das erste Themengebiet umfasst die Herstellung von Polymer/Calciumphosphat-Hybridpartikeln und –Hybridkapseln über die templatgesteuerte Mineralisation von Calciumphosphat. Die funktionalisierte Oberfläche von Polymernanopartikeln, welche über die Miniemulsionspolymerisation hergestellt wurden, diente als Templat für die Kristallisation von Calciumphosphat auf den Partikeln. Der Einfluss der funktionellen Carboxylat- und Phosphonat-Oberflächengruppen auf die Komplexierung von Calcium-Ionen sowie die Mineralisation von Calciumphosphat auf der Oberfläche der Nanopartikel wurde mit mehreren Methoden (ionenselektive Elektroden, REM, TEM und XRD) detailliert analysiert. Es wurde herausgefunden, dass die Mineralisation bei verschiedenen pH-Werten zu vollkommen unterschiedlichen Kristallmorphologien (nadel- und plättchenförmige Kristalle) auf der Oberfläche der Partikel führt. Untersuchungen der Mineralisationskinetik zeigten, dass die Morphologie der Hydroxylapatit-Kristalle auf der Partikeloberfläche mit der Änderung der Kristallisationsgeschwindigkeit durch eine sorgfältige Wahl des pH-Wertes gezielt kontrolliert werden kann. Sowohl die Eigenschaften der als Templat verwendeten Polymernanopartikel (z. B. Größe, Form und Funktionalisierung), als auch die Oberflächentopografie der entstandenen Polymer/Calciumphosphat-Hybridpartikel wurden gezielt verändert, um die Eigenschaften der erhaltenen Kompositmaterialien zu steuern. rnEine ähnliche bio-inspirierte Methode wurde zur in situ-Herstellung von organisch/anorganischen Nanokapseln entwickelt. Hierbei wurde die flexible Grenzfläche von flüssigen Miniemulsionströpfchen zur Mineralisation von Calciumphosphat an der Grenzfläche eingesetzt, um Gelatine/Calciumphosphat-Hybridkapseln mit flüssigem Kern herzustellen. Der flüssige Kern der Nanokapseln ermöglicht dabei die Verkapselung unterschiedlicher hydrophiler Substanzen, was in dieser Arbeit durch die erfolgreiche Verkapselung sehr kleiner Hydroxylapatit-Kristalle sowie eines Fluoreszenzfarbstoffes (Rhodamin 6G) demonstriert wurde. Aufgrund der intrinsischen Eigenschaften der Gelatine/Calciumphosphat-Kapseln konnten abhängig vom pH-Wert der Umgebung unterschiedliche Mengen des verkapselten Fluoreszenzfarbstoffes aus den Kapseln freigesetzt werden. Eine mögliche Anwendung der Polymer/Calciumphosphat-Partikel und –Kapseln ist die Implantatbeschichtung, wobei diese als Bindeglied zwischen künstlichem Implantat und natürlichem Knochengewebe dienen. rnIm zweiten Themengebiet dieser Arbeit wurde die Grenzfläche von Nanometer-großen Miniemulsionströpfchen eingesetzt, um einzelne in der dispersen Phase gelöste Polymerketten zu separieren. Nach der Verdampfung des in den Tröpfchen vorhandenen Lösungsmittels wurden stabile Dispersionen sehr kleiner Polymer-Nanopartikel (<10 nm Durchmesser) erhalten, die aus nur wenigen oder einer einzigen Polymerkette bestehen. Die kolloidale Stabilität der Partikel nach der Synthese, gewährleistet durch die Anwesenheit von SDS in der wässrigen Phase der Dispersionen, ist vorteilhaft für die anschließende Charakterisierung der Polymer-Nanopartikel. Die Partikelgröße der Nanopartikel wurde mittels DLS und TEM bestimmt und mit Hilfe der Dichte und des Molekulargewichts der verwendeten Polymere die Anzahl an Polymerketten pro Partikel bestimmt. Wie es für Partikel, die aus nur einer Polymerkette bestehen, erwartet wird, stieg die mittels DLS bestimmte Partikelgröße mit steigendem Molekulargewicht des in der Synthese der Partikel eingesetzten Polymers deutlich an. Die Quantifizierung der Kettenzahl pro Partikel mit Hilfe von Fluoreszenzanisotropie-Messungen ergab, dass Polymer-Einzelkettenpartikel hoher Einheitlichkeit hergestellt wurden. Durch die Verwendung eines Hochdruckhomogenisators zur Herstellung der Einzelkettendispersionen war es möglich, größere Mengen der Einzelkettenpartikel herzustellen, deren Materialeigenschaften zurzeit näher untersucht werden.rn

The role of the interplay between polymer architecture and bacterial surface properties on the microbial adhesion to polyoxazoline-based ultrathin films

Surface platforms were engineered from poly(L-lysine)-graft-poly(2-methyl-2-oxazoline) (PLL-g-PMOXA) copolymers to study the mechanisms involved in the non-specific adhesion of Escherichia coli (E. coli) bacteria. Copolymers with three different grafting densities (PMOXA chains/Lysine residue of 0.09, 0.33 and 0.56) were synthesized and assembled on niobia (Nb O ) surfaces. PLL-modified and bare niobia surfaces served as controls. To evaluate the impact of fimbriae expression on the bacterial adhesion, the surfaces were exposed to genetically engineered E. coli strains either lacking, or constitutively expressing type 1 fimbriae. The bacterial adhesion was strongly influenced by the presence of bacterial fimbriae. Non-fimbriated bacteria behaved like hard, charged particles whose adhesion was dependent on surface charge and ionic strength of the media. In contrast, bacteria expressing type 1 fimbriae adhered to the substrates independent of surface charge and ionic strength, and adhesion was mediated by non-specific van der Waals and hydrophobic interactions of the proteins at the fimbrial tip. Adsorbed polymer mass, average surface density of the PMOXA chains, and thickness of the copolymer films were quantified by optical waveguide lightmode spectroscopy (OWLS) and variable-angle spectroscopic ellipsometry (VASE), whereas the lateral homogeneity was probed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Streaming current measurements provided information on the charge formation of the polymer-coated and the bare niobia surfaces. The adhesion of both bacterial strains could be efficiently inhibited by the copolymer film only with a grafting density of 0.33 characterized by the highest PMOXA chain surface density and a surface potential close to zero.

Effects of unique ion chemistry on thin-film growth by plasma–surface interactions

Plasma processing is a standard industrial method for the modification of material surfaces and the deposition of thin films. Polyatomic ions and neutrals larger than a triatomic play a critical role in plasma-induced surface chemistry, especially in the deposition of polymeric films from fluorocarbon plasmas. In this paper, low energy CF3+ and C3F5+ ions are used to modify a polystyrene surface. Experimental and computational studies are combined to quantify the effect of the unique chemistry and structure of the incident ions on the result of ion-polymer collisions. C3F5+ ions are more effective at growing films than CF3+, both at similar energy/atom of ≈6 eV/atom and similar total kinetic energies of 25 and 50 eV. The composition of the films grown experimentally also varies with both the structure and kinetic energy of the incident ion. Both C3F5+ and CF3+ should be thought of as covalently bound polyatomic precursors or fragments that can react and become incorporated within the polystyrene surface, rather than merely donating F atoms. The size and structure of the ions affect polymer film formation via differing chemical structure, reactivity, sticking probabilities, and energy transfer to the surface. The different reactivity of these two ions with the polymer surface supports the argument that larger species contribute to the deposition of polymeric films from fluorocarbon plasmas. These results indicate that complete understanding and accurate computer modeling of plasma–surface modification requires accurate measurement of the identities, number densities, and kinetic energies of higher mass ions and energetic neutrals.

Tailored conductivity in ion implanted polyetheretherketone

Ion implantation can be used to confer electrical conductivity upon conventional insulating polymers such as polyetheretherketone (PEEK). We have implanted PEEK films using three different types of ion implantation: conventional inert gas and metal ion implantation, and ion beam mixing. We have applied a number of analytical techniques to compare the chemical, structural and electrical properties of these films. The most effective means of increasing electrical conductivity appears to be via ion beam mixing of metals into the polymer, followed by metal ion implantation and finally, inert gas ion implantation. Our results suggest that in all cases, the conducting region corresponds to the implanted layer in the near surface to a depth of similar to750 Angstrom (ion beam mixed) to similar to5000 Angstrom (metal ion). This latter value is significantly higher than would be expected from a purely ballistic standpoint, and can only be attributed to thermal inter-diffusion. Our data also indicates that graphitic carbon is formed within the implant region by chain scission and subsequent cross-linking. All ion implanted samples retained their bulk mechanical properties, i.e. they remained flexible. The implant layers showed no signs of de-lamination. We believe this to be the first comparative study between different implantation techniques, and our results support the proposition that soft electronic circuitry and devices can be created by conductivity engineering with ion beams. (C) 2004 Elsevier B.V. All rights reserved.

Selectivity of response in fluorescent polymers imprinted with N1-benzylidene pyridine-2-carboxamidrazones

Fluorescent polymers imprinted with various N1-benzylidene pyridine-2-carboxamidrazones were evaluated for their recognition of the original template and cross-reactivity to similar molecules. Dramatic quenching of fluorescence approaching background levels was observed for most cases where the "empty" MIP was re-exposed to its template. Molecules too large to enter the imprinted cavities gave no reduction of fluorescence. Other compounds were found to quench the fluorescence and are assumed to have entered the imprinted cavities. There is also evidence for partial responses which may give some measure of partial binding. The fluorescence response profiles of substrates containing polycyclic aromatics were found to be quite different from those containing flexible substituents. In order to make this approach more suitable for high-throughput screening a method has been validated wherein the extent of substrate-induced fluorescence quenching may be obtained without having to know how much polymer is present. © 2001 Elsevier Science B.V. All rights reserved.

Quantifying hydrogel response using laser light scattering

The pH and counter-ion response of a microphase separated poly(methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) hydrogel has been investigated using laser light scattering on an imprinted micron scale topography. A quartz diffraction grating was used to create a micron-sized periodic structure on the surface of a thin film of the polymer and the resulting diffraction pattern used to calculate the swelling ratio of the polymer film in situ. A potentiometric titration and a sequence of counter ion species, taken from the Hofmeister series, have been used to compare the results obtained using this novel technique against small angle X-ray scattering (nanoscopic) and gravimetric studies of bulk gel pieces (macroscopic). For the first time, the technique has been proven to be an inexpensive and effective analytical tool for measuring hydrogel response on the microscopic scale.

Synthesis and characterisation of imprinted polymeric receptor mimics

Molecularly imprinted polymers (MIPs) are crosslinked polymers containing bespoke functionalised cavities arising from the inclusion of template molecules in the polymerisation mixture and their later extraction. When the polymers are prepared functional polymerisable monomers are included which become part of the polymer matrix and serve to decorate the cavities with functionality appropriate to the template molecules. Overall, binding sites are created which have a memory for the template both in terms of shape and matching functionality. Fluorescent molecularly imprinted polymers have the benefit of a fluorophore in their cavities that may respond to the presence of bound test compound by a change in their fluorescence output. The work presented falls into three main areas. A series of fluorescent MIPs was prepared with a view to generating material capable of mimicking the binding characteristics of the metabolically important cytochrome isoform CYP2D6. The MIPs re-bound their templates and various cross-reactivities were encountered for test compound/drug recognition. One MIP in particular exhibited a rational discrimination amongst the related synthetic templates and was reasonably successful in recognising CYP2D6 substrates from the drug set tested. In order to give some insights into binding modes in MIPs, attempts were made to produce functional monomers containing two or more fluorophores that could be interrogated independently. A model compound was prepared which fitted the dual-fluorophore criteria and which will be the basis for future incorporation into MIPs. A further strand to this thesis is the deliberate incorporation of hydrophobic moieties into fluorescent functional monomers so that the resulting imprinted cavities might be biomimetic in their impersonation of enzyme active sites. Thus the imprinted cavities had specific hydrophobic regions as well as the usual polar functionality with which to interact with binding test compounds.