This thesis is concerned with ion-ion and ion-polymer interactions over a wide concentration range in polymer electrolytes with a view to shedding new light on the mechanism of ion migration. Additionally, the electrochemical stability window of these electrolytes on platinum and vitreous carbon electrodes has been thoroughly investigated. The final part of this thesis is concerned with determining the feasibility of polymer electrolytes as electrolytes in a new type of energy storage device, a double layer capacitor which incorporates activated carbon cloth electrodes. Conductivities and viscosities of solutions of Li, Na and K thiocyanates in low-molecular-weight, non-crystallizable liquid copolymers of ethylene oxide (EO) and propylene oxide (PO) have been measured. The curves of molar conductance versus sqrt c show well-defined maxima and minima. The conductivity is independent of copolymer molecular-weight but is enhanced by raising the EO content of the copolymer. The results are interpreted in terms of a model for ion migration in which ion association and redissociation effects play an important role. It is proposed that the characteristic properties of liquid polymer electrolytes can only be satisfactorily explained if the current is largely anionic. The electrochemical stability window of these electrolytes on platinum is dominated by the presence of a water reduction peak starting at approximately -1.0V which limits the overall stability to approximately 2V. The onset of water reduction is displaced to more negative potentials (-3.0V), thus increasing the stability window, on vitreous carbon electrodes. The value of the double layer capacitance on vitreous carbon electrodes (15-30muF cm-2) agrees well with published data. The double layer capacitance of activated carbon cloth electrodes is lower than anticipated. The importance of faradaic charging and discharging currents to the successful operation of double layer capacitors is indicated but no problems relating to the specific use of polymer electrolytes in such devices were found.

The interaction between thin films of polymethyi methacrylate and polyethylene terephthalate is reported. Studies of bulk PET/PMMA blends reveal that a direct ester exchange reaction occurs between the two polymers, and this information is used in the investigation of thin film interfaces between PET and PMMA. Discrete wavelength ellipsometry has been used to study the thermal decomposition of thin films of PMMA , and the crystallisation of thin films of PET. It is found that, below ~ 74.5 nm (6 x R(_g), the rate of degradation of PMMA (M(_N) ~ 44,000), increases with decreasing film thickness. For films < 100 nm , the rate of crystallisation of PET (M(_N) ~ 23,000), is found to decrease with decreasing film thickness. Using data obtained from neutron reflectometry, the equilibrium interfacial width between PET and dPMMA is measured. At an annealing temperature of 493K, the interface is broadened by crystalline roughness in the PET phase, and the maximum interfacial width is found to be ~7.7tmi. At 573K, despite extensive degradation of dPMMA, an equilibrium interfacial width of ~5nm is achieved. Capillary wave broadening and the effects of asymmetry are considered. A detailed analysis of Interfacial Marker Movements, reveals that there is an asymmetric broadening of the gold markers towards the PMMA side of the interface, indicative of a grafting reaction between PET and PMMA or a crosslinking reaction within the residual PMMA layer. The degradation of PET films, treated with acrylic based coating formulations has been studied by GPC, UV-vis spectrophotometry, and weight loss techniques. The rate of chain scission at 563K is seen to be dependant on the the concentration of tri methoxy methyl melamine (TMMM), the coating crosslinking agent.

The focus of the following research was to provide an optimized particle stabilized foam of Laponite and Pluronic L62 in water by understanding (1) the Laponite-Pluronic interactions and properties for improved performance in a particle stabilized foam and (2) the interfacial properties between air and the Laponite-Pluronic complex. These studies were conducted using both bulk and interfacial rheology, XRD, sessile droplet, TGA and UV-vis. Two novel and simple techniques, lamella break point and capillary breakup extensional rheometry, were used to both understand the Laponite Pluronic L62 interaction and determine a different mechanism for foaming properties. Bulk rheological properties identified an optimal Laponite concentration of 2% with Pluronic L62 ranging from 2.5% and 6.5%, due to the ease of flow for the dispersion. The Pluronic L62 was observed to enhance the Laponite bulk rheological properties in solution. Additionally TGA showed a similar trend in thermal resistance to water with both addition of Laponite and Pluronic L62. XRD demonstrated that 0.25% Pluronic intercalated into Laponite from dried 2% Laponite films. XRD demonstrated that the Laponite matrix was saturated at 1% Pluronic L62. UV-vis demonstrated that a monolayer of Pluronic L62 is observed up to 0.65% Pluronic L62 onto Laponite. Interfacial rheology showed that Laponite enhances Pluronic L62 at the air-liquid interface by improving the storage modulus as low at 0.65% Pluronic L62 with 2% Laponite. The lamella breakpoint of Laponite with Pluronic films indicate strong film interaction due to higher increases in mass. Extensional rheology indicates that 2.5% to 6.5% Pluronic with 2% Laponite show the most filament resistance to stretching.

No description available.

<p>Mikrokapsule, kao nosači aktivnih supstanci, imaju sve veću primenu u različitim granama industrije, naročito prehrambene i farmaceutske. Inkorporiranje biolo&scaron;ki aktivnih supstanci unutar mikrokapsula omogućava maskiranje neprijatnih mirisa i ukusa, za&scaron;titu osetljivih i lako isparljivih komponenata.<br />Cilj ove doktorske disertacije je dobijanje mikrokapsula za istovremeno inkorporiranje hidrosolubilnih i liposolubilnih aktivnih materija, radi njihove za&scaron;tite i kontrolisanog otpu&scaron;tanja. Mikrokapsule su formirane iz duplih emulzija tipa voda-ulje-voda (V/U/V) metodom koacervacije, odnosno deponovanjem koacervata, koji nastaje u sistemu dva suprotno naelektrisana proteina, želatina i natrijum kazeinata (NaKN), na granicu faza ulje/voda. Kao model supstance za hidrosolubilne i liposolubilne biolo&scaron;ki aktivne materije, kori&scaron;ćeni su vitamini C i E.<br />Najpre su detaljno ispitane interakcije u sistemu želatin/NaKN primenom različitih metoda (merenje zeta potencijala, tenziometrija, viskozimetrija, reolo&scaron;ka ispitivanja). Na osnovu ovih rezultata definisane su promene, kako na granici faza, tako i unutar rastvora, kao i mehanizama formiranja koacervata između ova dva suprotno naelektrisana proteina. Utvrđeno je da se pri masenom odnosu želatin:NaKN od 2:1 dolazi do formiranja nerastvornog koacervata. Ispitan je uticaj interakcija u ovom sistemu na osobine duplih, V/U/V emulzija dobijenih emulgovanjem primarnih voda/ulje (V/U) emulzija u sme&scaron;i želatin/NaKN, pri njihovim odabranim masenim odnosima i zaključeno je da interakcija između proteina u kontinualnoj fazi utiče na<br />osobine emulzija.<br />S obzirom da je prvi korak ka dobijanju stabilne V/U/V emulzije, dobijanje stabilne primarne V/U emulzije, ispitana je mogućnost primene lipofilnih emulgatora, poliglicerol poliricinoleata (PGPR) i poliglicerol estra jestivih masnih kiselina i njihovih sme&scaron;a, za dobijanje 20% V/U emulzija. Ispitivanjem uticaja sastava sme&scaron;e emulgatora i njegove koncentracije na formiranje adsorpcionog sloja na graničnoj povr&scaron;ini ulje/voda i osobine formiranih V/U emulzija odabran je najpogodniji sistem za stabilizaciju primarnih emulzija.<br />Nakon formulisanja stabilnih duplih V/U/V emulzija sa inkorporiranim vitaminima C i E, optimizovani su uslovi za dobijanje mikrokapsula umrežavanjem kompleksa proteina na kapima ulja pomoću genipina, a njihovo izdvajanje iz rastvora ostvareno je primenom Spray drying postupka. Karakterizacijom dobijenih mikrokapsula (ispitivanjem morfologije povr&scaron;ine, efikasnosti inkapsulacije vitamina C i E, kinetike otpu&scaron;tanja vitamina C u in vitro uslovima) zaključeno je da na osobine mikrokapsula utiče koncentracija umreživača, kao i interakcija između želatina i NaKN u kontinualnoj fazi emulzija V/U/V.</p> / <p>Microcapsules, as active substance carriers, have increasing application in different industries, especially in food and pharmaceutical industry. Incorporation of the biologically active substances inside the microcapsules allows masking of unpleasant taste and smell, protection od sensitive and volatile components.<br />The aim of this thesis is preparation of microcapsules for parallel incorporation of water and oil soluble active substances for their protection and controlled release. Microcapsules were formed from double water-oil-water emulsions (W/O/W) by coacervation method, depositing the coacervate formed in the system of two oppositely charged proteins, gelatin and sodium caseinate (NaCN), at the water/oil interface. As a model for water and oil soluble biological active substances, vitamins C and E were used.<br />First of all, interactions in the gelatin/NaCN system were investigated in detail, by using different methods (measuring of zeta potential, tensiometry, vicometry, rheological investigations). Based on these results, changes at the interface and in the bulk of the system, as well as mechanisms of coacervate formation were defined. It has been determined that at gelatin:NaCN mass ratio of 2:1 non soluble coacervate were formed.<br />Influence of the interactions in this system on properties of the W/O/W double emulsions, made by emulsification of primary water/oil (W/O) emulsions in gelatin/NaCN mixtures, at desired mass ratios of proteins, was investigated. It was concluded that interactions between proteins in continuous phase of emulsions have influence on their properties.<br />As the first step in formation of stable W/O/W emulsions is<br />obtaining stable primary W/O emulsion, possibility of using lipophilic emulsifiers, polyglycerol polyricinoleate (PGPR) and polyglycerol esters of edible fatty acids and their mixtures, for 20% W/O emulsions formation were investigated. Results of these investigations showed that composition of emulsifiers mixtures and their concentrations have an influence on adsorption layer, at the water/oil interface, formation, as well as on stability of W/O emulsion, and based on these results the most suitable system of emulsifiers were chosen.<br />After formulation of stable double W/O/W emulsions with incorporated vitamins C and E, conditions for microcapsules formation, by crosslinking of proteins complex at oil droplets with genipin, were optimized, and for their separation from dispersion spray drying method was applied. Characterization of obtained microcapsules (investigation of the surface morphology, efficiency of the vitamins C and E encapsulation, release kinetics of vitamin C under in vitro conditions) showed that concentration of crosslinking agent, as well as interaction between gelatin and NaCN, have an influence on microcapsules properties.</p>

The relationship between the amount and conformation of apolymer at the solid-liquid interface, and the resultinginteraction forces between two such surfaces has beeninvestigated. With a degree of control of the polymerconformation, by varying the temperature, solvent quality,polymer charge density etc, it has been possible to measure andinterpret the resulting changes in the surface interactions.The recurring themes of dynamics and hydrodynamics have beencontinually considered due to the large range and viscoelasticnature of the polymeric systems. The polymeric systems investigated in this thesis are, poly(N-isopropylacrylamide), poly (12-hydroxystearate) and a seriesof AM-MAPTAC polyelectrolytes with variable chargedensities. Adsorption and conformation of polymers have beeninvestigated by the novel QCM instrument. By comparison tosimultaneously measured energy loss information, a greaterunderstanding of the conformation of the polymer has beengained, both as a function of layer build-up during initialadsorption, and as a result of induced conformational changes.Comparing the results toin situsurface plasmon resonance and subsequent x-rayphotoelectron spectroscopy measurements, the relativeconcentration of polymer within the layer is determined. Inaddition, efforts have been made to extend the scope of thetechnique, in such ways as measuring with QCM as a function oftemperature and deriving viscoelastic properties. The later isstill to be achieved in absolute terms for polymer layers inliquid environments, yet both the principle and experimentalcapabilities have been shown. Normal interaction forces have been measured as a functionof solvation of the polymer layer, for both adsorbed andgrafted polymer layers. For fully solvated (steric) polymerlayers, which can act as colloidal stabilisers, the dynamics ofthe repulsive force, including hydrodynamics have beeninvestigated. The same has been achieved for collapsed polymerlayers, in which the dynamic adhesion has also beeninvestigated. The effect on the adhesion of three differentdynamic mechanisms has been determined (which, like the surfaceforces, depend on the polymer conformation andviscoelasticity). These dynamic mechanisms are based onbridging forces, polymer entanglement and a viscoelastic‘bulk’response from the surface layers. Lateral or friction measurements have also been completed.The effect of load and rate have been investigated as afunction of both the polymer charge density and the underlyingsubstrate, which result in a variable conformation and bindingstrength to the substrate. This has resulted in a complexaddition of numerous mechanisms, the dominant mechanism beingdetermined by the binding strength to the surface, polymerconformation and viscoelasticity. The results have shown thatadsorbed polymer layers can be used to both increase anddecrease friction, and to change the direction of the ratedependence.

<p>The relationship between the amount and conformation of apolymer at the solid-liquid interface, and the resultinginteraction forces between two such surfaces has beeninvestigated. With a degree of control of the polymerconformation, by varying the temperature, solvent quality,polymer charge density etc, it has been possible to measure andinterpret the resulting changes in the surface interactions.The recurring themes of dynamics and hydrodynamics have beencontinually considered due to the large range and viscoelasticnature of the polymeric systems.</p><p>The polymeric systems investigated in this thesis are, poly(N-isopropylacrylamide), poly (12-hydroxystearate) and a seriesof AM-MAPTAC polyelectrolytes with variable chargedensities.</p><p>Adsorption and conformation of polymers have beeninvestigated by the novel QCM instrument. By comparison tosimultaneously measured energy loss information, a greaterunderstanding of the conformation of the polymer has beengained, both as a function of layer build-up during initialadsorption, and as a result of induced conformational changes.Comparing the results to<i>in situ</i>surface plasmon resonance and subsequent x-rayphotoelectron spectroscopy measurements, the relativeconcentration of polymer within the layer is determined. Inaddition, efforts have been made to extend the scope of thetechnique, in such ways as measuring with QCM as a function oftemperature and deriving viscoelastic properties. The later isstill to be achieved in absolute terms for polymer layers inliquid environments, yet both the principle and experimentalcapabilities have been shown.</p><p>Normal interaction forces have been measured as a functionof solvation of the polymer layer, for both adsorbed andgrafted polymer layers. For fully solvated (steric) polymerlayers, which can act as colloidal stabilisers, the dynamics ofthe repulsive force, including hydrodynamics have beeninvestigated. The same has been achieved for collapsed polymerlayers, in which the dynamic adhesion has also beeninvestigated. The effect on the adhesion of three differentdynamic mechanisms has been determined (which, like the surfaceforces, depend on the polymer conformation andviscoelasticity). These dynamic mechanisms are based onbridging forces, polymer entanglement and a viscoelastic‘bulk’response from the surface layers.</p><p>Lateral or friction measurements have also been completed.The effect of load and rate have been investigated as afunction of both the polymer charge density and the underlyingsubstrate, which result in a variable conformation and bindingstrength to the substrate. This has resulted in a complexaddition of numerous mechanisms, the dominant mechanism beingdetermined by the binding strength to the surface, polymerconformation and viscoelasticity. The results have shown thatadsorbed polymer layers can be used to both increase anddecrease friction, and to change the direction of the ratedependence.</p>

<p dir="ltr">Amorphous solid dispersions (ASDs) are being widely used as enabling formulations for poorly water soluble drugs. An ASD is a molecular level mixture of an amorphous drug and a polymer to form a single-phase homogeneous blend. The amorphous form of a drug provides a higher transient solubility compared to equilibrium crystalline solubility, whereby the presence of a polymer of appropriate properties aids in crystallization inhibition. Polymers also improve the release rate of the drug from the ASD relative to the release rate of neat amorphous drug, specifically for release regimens where both drug and polymer release congruently. Hydroxypropyl methylcellulose acetate succinate (HPMCAS)-based ASDs tend to show congruent release of drug and polymer across multiple drug loadings, providing a significant dissolution improvement even beyond the amorphous solubility of a drug. Enteric polymers such as HPMCAS have been studied extensively in terms of enteric coated tablets but haven’t been explored in as much detail when molecularly dispersed with a drug as in case of ASDs. Literature shows not all ASDs are able to improve bioavailability of drugs. Such a failure to provide bioavailability advantage via certain ASDs could come from a randomized drug and polymer selection in the preformulation stage of drug product development which could fundamentally arise from the lack of understanding of the release mechanisms of ASDs. Given that HPMCAS is one of the most popularly used polymers for spray drying of ASDs in the pharmaceutical industry, investigating the release mechanisms of HPMCAS-based ASDs is critical. In this study, some of the key formulation design factors, such as drug-polymer interactions, different grades of polymer as well as dissolution media factors such as buffer capacity that impact the release performance of HPMCAS-based ASDs have been investigated. The results from this study are expected to contribute to the fundamental understanding of the failure mechanisms of HPMCAS-based ASDs, reducing empirical screening of drugs during the preformulation stage of the product development and enhance the success rate of ASDs.</p>

Nanoparticulate drug delivery systems (NDDS) such as nanocrystals, nanosuspensions, solid-lipid nanoparticles often formulated for the bioavailability enhancement of poorly soluble drug candidates are stabilized by a mixture of excipients including surfactants and polymers. Most literature studies have focused on the interaction of excipients with the NDDS surfaces while ignoring the interaction of excipients in solution and the extent to which the solution-state interactions influence the affinity and capacity of adsorption. Mechanisms by which excipients stabilize NDDS and how this information can be utilized by formulators a priori to make a rational selection of excipients is not known. The goals of this dissertation work were (a) to determine the energetics of interactions between HPMC and model surfactants and the extent to which these solution-state interactions modulate the adsorption of these excipients onto solid surfaces, (b) to determine and characterize the structures of various aggregate species formed by the interaction between hydroxypropyl methylcellulose (HPMC) and model surfactants (nonionic and ionic) in solution-state, and (c) to extend these quantitative relationships to interpret probable mechanisms of mixed adsorption of excipients onto the model NDDS surface. A unique approach utilizing fluorescence, solution calorimetry and adsorption isotherms was applied to tease apart the effect of solution state interactions of polymer and surfactant on the extent of simultaneous adsorption of the two excipients on a model surface. The onset of aggregation and changes in aggregate structures were quantified by a fluorescence probe approach with successive addition of surfactant. In the presence of HPMC, the structures of the aggregates formed were much smaller with an aggregation number (Nagg) of 34 as compared to micelles (Nagg ~ 68) formed in the absence of HPMC. The strength of polymer-surfactant interactions was determined to be a function of ionic strength and hydrophobicity of surfactant. The nature of these structures was characterized using their solubilization power for a hydrophobic probe molecule. This was determined to be approximately 35% higher in the polymer-surfactant aggregates as compared to micelles alone and was attributed to a significant increase in the number of aggregates formed and the increased hydrophobic microenvironment within these aggregates at a given concentration of surfactant. The energetics of the adsorption of SDS, HPMC, and SDS-HPMC aggregate onto nanosuspensions of silica, which is the model solid surface were quantified. A strong adsorption enthalpy of 1.25 kJ/mol was determined for SDS adsorption onto silica in the presence of HPMC as compared to the negligible adsorption enthalpy of 0.1 kJ/mol for SDS alone on the silica surface. The solution depletion and HPMC/ELSD methods showed a marked increase in the adsorption of SDS onto silica in the presence of HPMC. However, at high SDS concentrations, a significant decrease in the adsorbed amount of HPMC onto silica was determined. This was further corroborated by the adsorption enthalpy that showed that the silica-HPMC-SDS aggregation process became less endothermic upon addition of SDS. This suggested that the decrease in adsorption of HPMC onto silica at high SDS concentrations was due to competitive adsorption of SDS-HPMC aggregates wherein SDS is displaced/desorbed from silica in the presence of HPMC. At low SDS concentrations, an increase in adsorption of SDS was due to cooperative adsorption wherein SDS is preferentially adsorbed onto silica in the presence of HPMC. This adsorption behavior confirmed the hypothesis that the solution-state interactions between pharmaceutical excipients such as polymers and surfactants would significantly impact the affinity and capacity of adsorption of these excipients on NDDS surfaces.

The aim of this study was to investigate the molecular interactions of the anti-cancer drug Doxorubicin (DOX) with poly(methacrylic acid) grafted starch nanoparticles (PMAA-g-St). In order to fully understand the DOX/PMAA-g-St system, we conducted in-depth studies on DOX dimer dissociation and DOX/PMAA-g-St binding interactions using various techniques such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and fluorescence and absorption spectroscopy. Based on our experimental results, we developed a quantitative thermodynamic model with relevant parameters such as dissociation constant, Kd, as well as enthalpy of binding, ΔH, in order to explain DOX/PMAA-g-St interactions. In addition, we also studied the effect of environmental factors such as pH and NaCl on DOX self-association and DOX/PMAA-g-St complex formation. In conclusion, the combination of results obtained from various techniques as well as the multispecies equilibrium model, enables us to interpret quantitatively the data of drug loading onto and release from polymeric nanoparticles.