Regensburg, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Göttingen, Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Regensburg, University, Diss., 2002.

Göttingen, Universiẗat, Diss., 2003.

No description available.

The removal of lead, copper and cadmium ions from aqueous streams using lecithin enhanced micro filtration with 0.2μm pore size tubular ceramic membranes has been investigated. Measurements of the surface tension at varying lecithin concentrations were carried out to determine the critical micelle concentration (CMC) of lecithin and the effects of lead ions, mixtures of lead and copper ions, and mixtures of lead, copper and cadmium ions in solutions on the CMC of lecithin. The zeta potential and the effects of the single and multiple metal ions on the zeta potential of lecithin were also investigated. The influence of lecithin concentrations, cross flow velocity and transmembrane pressure on the rejections and steady state permeate flux behaviours were examined. The CMC of lecithin was found to be 9 grl. An increase in metal ion concentration caused a decrease in the CMC and an increase in the zeta potential of lecithin solutions, suggesting the binding of the metal ions onto the lecithin. An increase in lecithin concentration was found to improve metal ions removal. Lecithin showed preference for the metal ions in the order Pb2+ > Cd 2+ > Cu 2+. Metal ion removal was influenced more by lecithin concentration and less by transmembrane pressure and cross flow velocity. The steady state permeate flux and rejection behaviours have been explained by microscopic phenomena and a mathematical model has been developed to predict the steady state permeate flux. The lecithin concentration that remains in the permeate was less than 9% of the feed solution. The study has shown that lecithin enhanced micro filtration is a technically suitable technique for removal of lead, copper and cadmium ions in aqueous solution.

1 / Bin Meng

Many chromophoric organics and polymers are highly emissive in their dilute solutions but become weakly luminescent in the high concentration and solid film states due to the induced £k−£k interactions of the intimately-contact chromophores. Therefore, it is practically important to develop fluorescent organic and polymeric materials with enhanced emission in their aggregated states (so called aggregated-induced emission, AIE). In this study, organic compound 2,4-diphenylquinoline (DPQ) with inherent quinoline ring and polymeric poly(vinyl diphenylquinoline) (PVQ) with pendant quinoline group were prepared and their AIE-phenomena were characterized. To prove the reported point that restriction of intramolecular rotation (RIR) is the main cause for AIE effect, DPQ and PVQ were further incorporated with organic strong acid of camphorsulfonic acid (CSA). Through the favorable acid-base interaction between the sulfonic acid in CSA and the nitrogen atom of the quinoline ring in DPA (or CSA), ionic complex of DPQ-CSA (and PVQ-CSA) was easily prepared and their response toward AIE properties were studied. Through the enhanced RIR by the complexation of bulky CSA with the central quinoline ring, the resulting DPQ-CSA (and PVQ-CSA) complex was proved to have better AIE-effect compared to the pristine DPQ (and PVQ). RIR mechanism can be indirectly proved in this case. We study the AIE on micelle topics of the block copolymer. We choose the poly(styrene-block-tertbutylstyrene) (PS-b-PBS) as our block copolymer. To synthesize the PS-b-PBS, we can successfully get the new block copolymer PVQ-b-PBS. PVQ-b-PBS was similarly blended with the CSA. In the block copolymer micelles, choose the selective solvent to get the different micelles and observe the diverse on the luminescence. Finally, we analyzed compositions and conformations by atomic force microscopy (AFM) and transmission electron microscopy (TEM).

Abstract: Stimuli-responsive polymers and their assemblies, such as micelles, block copolymer (BCP) vesicles and hydrogels, can be dissociated or become relatively permeable upon excitation with a stimulus. This stimuli-responsive feature has made them very attractive carriers or vectors in drug delivery applications, since it is possible to realize controllable release of payloads from these systems by using, for example, light as a trigger enabling remote activation, and spatial and temporal control of the release. The research work presented in this thesis consists of two parts. The first part is focused on the design, synthesis and study of several novel photoresponsive polymers forming micelles, vesicles and hydrogels, as well as their exploitation for potential drug delivery applications. The second part concerns a study of the use of a different stimulus, namely, dissolved carbon dioxide (CO2). A general approach of using dissolved gases to manipulate the structural and morphological transition of BCP vesicles is described. The core of this thesis is five publications resulting from different projects that constitute the research work accomplished in our studies. In the first project, we developed a new strategy to prepare photo-dissociable BCP vesicles. By synthesizing a novel photoresponsive BCP with spiropyran and controlling the preparation conditions, a kinetically stable BCP vesicle was obtained at high pH (pH=8) due to the glassy membrane. Upon UV irradiation, fast BCP vesicle dissociation was achieved through a cascade of events triggered by the photoinduced isomerization from neutral spiropyran to charged merocyanine in the membrane. In second project, we demonstrated a novel strategy to tune the permeability of BCP vesicle membrane by taking advantage of the photoinduced liquid crystal (LC) order-disorder transition occurring inside the membrane. To this end, we designed and synthesized two series of amphiphilic BCPs of which the hydrophobic block is a side-chain liquid crystalline polymer bearing a small amount of azobenzene groups. Both BCPs could form giant BCP vesicles in aqueous solutions, facilitating their direct observation by optical microscopy. From polarized optical measurement, it was found that a photoinduced LC order—disorder transition could occur inside the vesicle membrane in aqueous solutions. This photoinduced transition has a softening effect on the membrane similar to that caused by good organic solvents. By using a fluorescent probe, we found that this photoinduced softening effect could increase the membrane permeability to proton diffusion. In the third project, we demonstrated a possibly universal solution to solve the problem of requiring UV or visible light excitation to trigger the response of many photosensitive materials developed for biomedical applications. The strategy consists in disrupting photoresponsive BCP micelles by using near-infrared (NIR) light excitation of upconverting nanoparticles (UCNPs). By encapsulating UCNPs into micelles of a photoresponsive BCP containing o-nitrobenzyl groups, UV photons emitted from UCNPs upon 980 nm NIR light excitation using a continuous-wave diode laser can be absorbed by o-nitrobenzyl groups in the micelle core, activating their photocleavage reaction and resulting in micelle dissociation and release of co-loaded hydrophobic compounds. The idea of using UCNPs as a nanoscale UV or visible light source upon NIR light excitation to activate photoreactions in photosensitive materials is of great significance. The strategy is general and can be applied to many photosensitive polymeric materials whose potential for biomedical applications is limited due to the wavelength issue. In the fourth project, we further investigated the generality of using UCNPs to circumvent the wavelength problem of most photoresponsive polymer systems. We extended the application of the approach to photoresponsive hydrogels. UCNPs were loaded into a hydrogel whose gel-sol transition requires UV light-induced breaking of the network structure. Upon 980 nm laser irradiation, the gel-sol transition was achieved by UV light emitted from UCNPs. This feature allowed us to realize NIR light-triggered release of large, inactive biomacromolecules (protein and enzyme) entrapped in the hydrogel into aqueous solution "on demand", where their bioactivity is recovered. The last project dealt with the use of CO2 as a smart trigger to switch a specific property or function of stimuli-responsive polymers. We put forward a general way to prepare CO2-responsive BCP vesicles by using the commercially available poly(N,N',-diethylaminoethyl methacrylate) (PDEAEMA) as the hydrophobic block forming the vesicle membrane. We showed that vesicles can either be completely dissociated (with uncrosslinked PDEAEMA) or undergo reversible volume expansion up to 2100% (with slightly crosslinked PDEAEMA) upon introduction of the gas into the solution. The drastic changes induced by dissolved CO2 are unprecedented. This study is a new demonstration of designing easily accessible CO2-responsive polymers and opens perspectives for valorizing CO2 in polymer and material sciences.//Résumé: Les polymères répondant aux stimuli et leurs assemblages sous forme de micelles, de vésicules ou d'hydrogels, peuvent être dissociés ou devenir relativement perméables des suites de l'application d'une excitation. Cette fonctionnalité stimuli-réponse les rend très attrayants en tant que transporteurs ou comme vecteurs pour le relargage ciblé de médicaments. Elle permet de réaliser la libération contrôlée des charges utiles de ces systèmes en utilisant, par exemple, la lumière comme un déclencheur permettant l'activation à distance, et le contrôle temporel de la libération. Les travaux présentés dans cette thèse sont regroupés en deux parties. La première décrit la conception, la synthèse et l'étude de nouveaux polymères photosensibles formant des micelles, des vésicules et des hydrogels, ainsi que leur exploitation pour largage de molécules modélisant des agents thérapeutiques (i.e., médicaments). La seconde partie porte sur une étude de l'utilisation d'un stimulus différent, à savoir le dioxyde de carbone (CO2 ). Une approche générale basée sur l'utilisation de gaz afin de manipuler la transition structurale et morphologique des vésicules est décrite. Le noyau de cette thèse est constitué de cinq publications issues de différents projets qui sont représentatifs des travaux de recherche accomplis dans ces études de doctorat. Dans le premier projet, nous avons développé une nouvelle stratégie pour préparer des vésicules photo-dégradables. La synthèse d'un nouveau copolymère photosensible comprenant des unités spiropyranes et le contrôle des conditions de préparation a permis la préparation de vésicules cinétiquement stables à un pH élevé (pH = 8 ) en raison du caractère vitreux de la membrane. Lors d'irradiations UV, une dissociation rapide des vésicules a été accomplie grâce à une cascade d'événements déclenchés par l'isomérisation photo-induite de la spiropyrane (neutre) en mérocyanine (chargée) au sein de leur membrane. Dans le second projet, nous avons démontré une nouvelle stratégie pour moduler la perméabilité de la membrane des vésicules en exploitant une transition liquide-cristalline photo-induite afin d'accroître le désordre au sein de la membrane. À cet effet, nous avons conclu et synthétisé deux séries de copolymères à blocs amphiphiles dont la séquence hydrophobe est un polymère liquide cristallin à chaîne latérale portant une petite quantité de groupes azobenzène. Les deux copolymères furent utilisés pour préparer des vésicules géantes en solutions aqueuses, ce qui a permis leur observation directe par microscopie optique. De plus, une transition ordre-désordre photo-induite a été observée à l'intérieur de la membrane liquide cristalline des vésicules par microscopie à lumière polarisée. Cette transition photo-induite a un effet assouplissant sur la membrane semblable à celle causée par de bons solvants organiques. En utilisant une sonde fluorescente, nous avons observé que cet accroissement de la souplesse de la membrane polymère causait l'augmentation de la perméabilité de la membrane à la diffusion de protons. Dans le troisième projet, nous avons démontré une solution possiblement universelle permettant de résoudre le problème résultant de la nécessité d'utiliser une excitation lumineuse UV ou visible comme stimulus de nombreux matériaux photosensibles développés pour des applications biomédicales. La stratégie consiste à irradier indirectement des micelles de copolymères photosensibles par le biais de la conversion ascendante de la proche infrarouge par des nanoparticules. Les photons UV émis par ces nanoparticules encapsulées à l'intérieur des micelles et irradiées en utilisant une diode laser à onde continue de 980nm sont absorbés par les groupes o-nitrobenzyle dont est constitué le copolymère photosensible, conduisant à l'activation de leur réaction de photo-clivage, à la dissociation des micelles et finalement, à la libération de composés hydrophobes. L'idée d'utiliser la conversion ascendante issue de nanoparticules irradiées dans la proche infrarouge comme source lumineuse nanoscopique dans l'UV ou le visible pour activer des réactions photochimiques dans des matériaux photosensibles est d'une grande importance. La stratégie est générale et peut être appliquée à de nombreux matériaux polymères photosensibles dont le potentiel pour des applications biomédicales est présentement limité en raison de la faible pénétration des rayonnements UV et visible dans les tissus. Dans le quatrième projet, nous avons étudié davantage la généralité de l'utilisation de la conversion ascendante par des nanoparticules afin de contourner le problème de longueur d'onde pour l'activation de la plupart des systèmes polymères photosensibles. Nous avons ainsi étendu l'application de l'approche à des hydrogels photosensibles. Les nanoparticules ont été chargées au sein d'un hydrogel dont la transition gel-sol nécessite de la lumière UV afin d'induire la rupture de la structure du réseau. Sous irradiation à l'aide d'une diode laser à 980 nm, la transition gel-sol a été stimulée par la lumière ultraviolette émise par la conversion ascendante issue des nanoparticules. Cette "fonction" nous a permis de déclencher, par irradiation dans l'infrarouge proche qui pénètre beaucoup plus profondément dans les tissus biologiques, la libération "à la demande" de macromolécules biologiques (protéines et enzymes), inactives lorsque piégées dans l'hydrogel, en solution aqueuse où leur activité est restaurée. Le dernier projet porte sur l'utilisation du CO2 comme un déclencheur intelligent pour activer une propriété ou une fonction spécifique de polymères dont la sensibilité à ce stimulus est programmée au sein de leur structure moléculaire. Nous avons proposé une façon générale pour préparer des vésicules copolymères sensibles au CO2 par l'inclusion d'un bloc hydrophobe de poly (N, N ',-diéthylaminoéthylmethacrylate) (PDEAEMA) disponible commercialement et formant la membrane de la vésicule. On a montré que ces vésicules peuvent être soit complètement dissociées (lorsque le PDEAEMA n'est pas réticulé) ou encore subir une expansion de volume réversible atteignant 2100% (lorsque le PDEAEMA est faiblement réticulé) en réponse à l'introduction de CO2 dissout dans la solution de vésicules. Les changements radicaux induits par la modulation de la concentration du CO2 dissout sont sans précédent. Cette étude est une nouvelle démonstration d'une conception facilement accessible de polymères dont la structure moléculaire est programmée pour répondre à cette modulation dans la concentration du CO2 dissout et ouvre des perspectives de valorisation du CO2 en sciences des matériaux et des polymères. [symboles non conformes]

Research Doctorate - Doctor of Philosophy (PhD) / The adsorption characteristics of pH responsive tertiary amine methacrylate-based diblock copolymers have been investigated. The main focus of this work is on poly(2-(dimethylamino)ethyl methacrylate-b-poly(2-(diethylamino)ethyl methacrylate (PDMA-b-PDEA) adsorption to the silica/aqueous solution interface at pH 9. Differing degrees of polymerisation and quaternisation were investigated with some attention given to variation of the block hydrophobicity utilising poly(2-(dimethylamino)ethyl methacrylate-b-poly(2-(diisopropylamino)ethyl methacrylate (PDMA-b-PDPA). Principally, optical reflectometry (OR) and atomic force microscopy (AFM) have been employed to monitor the adsorption in terms of adsorbed mass and layer morphology. A variety of other techniques have been utilised to provide ancillary information, including quartz crystal microbalance, zeta potential, dynamic light scattering and contact angle measurements. The combined results have provided a comprehensive understanding of the adsorption characteristics for the copolymers studied. Micelles of the tertiary amine methacrylate-based copolymers adsorbed readily to silica from aqueous solution at pH 9. The adsorption isotherms were determined, exhibiting a high affinity Langmuirian shape where the CMC did not appear to impact on the adsorbed mass. The adsorption was rationalised by the interaction between the cationic PDMA corona of the micelles with the negatively charged substrate. The more hydrophobic PDEA core block increased the level of adsorption above that observed for the PDMA homopolymer. It was shown that the adsorbed layers were robust to rinsing with electrolyte at high pH, although reduction of the pH to 4 yielded significant desorption. The adsorbed layer morphology observed by in situ AFM exhibited distinct micellar structures. The combined adsorbed mass and AFM images showed a significantly higher surface aggregation number than the measured solution aggregation number, indicating a more complex adsorption process than simple direct micelle adsorption. The adsorption kinetics were studied to elucidate the adsorption mechanism and revealed complex dynamic processes. Particular focus was given to the adsorption of 0q PDMA93-b-PDEA24 where the impact of concentration was evident and three mechanistic regimes could be defined; below the CMC, just above the CMC and far above the CMC. Interestingly, the adsorption process just above the CMC indicates a surface aggregation mechanism, while well above the CMC, the adsorption proceeds via a process that includes both direct micelle and unimer adsorption. On longer timescales, the adsorption at higher concentrations revealed an additional induction period of micelle relaxation on the surface that allowed for further adsorption. Increasing the PDMA quaternisation was found to reduce post adsorption rearrangement and as result equilibrium was reached more quickly for the highly quaternised analogues. The response of the adsorbed PDMA-b-PDEA copolymer films to multiple changes in solution pH (9 and 4) was monitored. After the initial desorption of copolymer with rinsing at pH 9 and then at pH 4, the adsorbed mass of copolymer was found to be constant with multiple cycles of pH. The remaining robust adsorbed layers, then exhibited reversible uptake and release of water with multiple pH cycles as measured by QCM. This observation was readily rationalised by the observed changes in copolymer charge (and hence hydrophobicity) affecting the interaction of the copolymer chains with the surrounding solution. While these characteristics were found to be reversible with pH cycling it was found that the initial micelle structure of the adsorbed film was lost upon the first rinse to pH 4. Finally, the first low Tg micelle-micelle multilayers of up to six layers were constructed using alternating layers of cationic and anionic tertiary amine methacrylate-based copolymers at pH 9. The existence of true micellar structures within each layer was proven using in situ AFM imaging where the alternating layer characteristics were supported by measured force curves. The construction of the individual micelle layers was also monitored by OR, where clear evidence of layer build-up was shown. In addition, each layer was robust to rinsing with electrolyte at the adsorbing pH, although, the stability of the formed multilayer was found to be limited to six layers. Upon reduction of the pH, almost all the adsorbed material was instantaneously removed from the surface. The stimulus-responsive nature of such multilayer films augurs well for potential controlled uptake/release applications. These findings should greatly encourage a larger research focus on micelle-micelle multilayers.