@phdthesis{Tan2011,
  author    = {Tan, Irene},
  title     = {Towards greener stationary phases : thermoresponsive and carbonaceous chromatographic supports},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53130},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Polymers which are sensitive towards external physical, chemical and electrical stimuli are termed as 'intelligent materials' and are widely used in medical and engineering applications. Presently, polymers which can undergo a physical change when heat is applied at a certain temperature (cloud point) in water are well-studied for this property in areas of separation chemistry, gene and drug delivery and as surface modifiers. One example of such a polymer is the poly (N-isopropylacrylamide) PNIPAAM, where it is dissolved well in water below 32 oC, while by increasing the temperature further leads to its precipitation. In this work, an alternative polymer poly (2-(2-methoxy ethoxy)ethyl methacrylate-co- oligo(ethylene glycol) methacrylate) (P(MEO2MA-co-OEGMA)) is studied due to its biocompatibility and the ability to vary its cloud points in water. When a layer of temperature responsive polymer was attached to a single continuous porous piece of silica-based material known as a monolith, the thermoresponsive characteristic was transferred to the column surfaces. The hybrid material was demonstrated to act as a simple temperature 'switch' in the separation of a mixture of five steroids under water. Different analytes were observed to be separated under varying column temperatures. Furthermore, more complex biochemical compounds such as proteins were also tested for separation. The importance of this work is attributed to separation processes utilizing environmentally friendly conditions, since harsh chemical environments conventionally used to resolve biocompounds could cause their biological activities to be rendered inactive.},
  language  = {en}
}
@phdthesis{Federico2011,
  author    = {Federico, Stefania},
  title     = {Synthetic peptides derived from decorin as building blocks for biomaterials based on supramolecular interactions},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59661},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In this work, the development of a new molecular building block, based on synthetic peptides derived from decorin, is presented. These peptides represent a promising basis for the design of polymer-based biomaterials that mimic the ECM on a molecular level and exploit specific biological recognition for technical applications. Multiple sequence alignments of the internal repeats of decorin that formed the inner and outer surface of the arch-shaped protein were used to develop consensus sequences. These sequences contained conserved sequence motifs that are likely to be related to structural and functional features of the protein. Peptides representative for the consensus sequences were synthesized by microwave-assisted solid phase peptide synthesis and purified by RP-HPLC, with purities higher than 95 mol\%. After confirming the desired masses by MALDI-TOF-MS, the primary structure of each peptide was investigated by 1H and 2D NMR, from which a full assignment of the chemical shifts was obtained. The characterization of the peptides conformation in solution was performed by CD spectroscopy, which demonstrated that using TFE, the peptides from the outer surface of decorin show a high propensity to fold into helical structures as observed in the original protein. To the contrary, the peptides from the inner surface did not show propensity to form stable secondary structure. The investigation of the binding capability of the peptides to Collagen I was performed by surface plasmon resonance analyses, from which all but one of the peptides representing the inner surface of decorin showed binding affinity to collagen with values of dissociation constant between 2•10-7 M and 2.3•10-4 M. On the other hand, the peptides representative for the outer surface of decorin did not show any significant interaction to collagen. This information was then used to develop experimental demonstration for the binding capabilities of the peptides from the inner surface of decorin to collagen even when used in more complicated situations close to possible appications. With this purpose, the peptide (LRELHLNNN) which showed the highest binding affinity to collagen (2•10-7 M) was functionalized with an N-terminal triple bond in order to obtain a peptide dimer via copper(I)-catalyzed cycloaddition reaction with 4,4'-diazidostilbene-2,2'-disulfonic acid. Rheological measurements showed that the presence of the peptide dimer was able to enhance the elastic modulus (G') of a collagen gel from ~ 600 Pa (collagen alone) to ~ 2700 Pa (collagen and peptide dimer). Moreover, it was shown that the mechanical properties of a collagen gel can be tailored by using different molar ratios of peptide dimer respect to collagen. The same peptide, functionalized with the triple bond, was used to obtain a peptide-dye conjugate by coupling it with N-(5'-azidopentanoyl)-5-aminofluorescein. An aqueous solution (5 vol\% methanol) of the peptide dye conjugate was injected into a collagen and a hyaluronic acid (HA) gel and images of fluorescence detection showed that the diffusion of the peptide was slower in the collagen gel compared to the HA gel. The third experimental demonstration was gained using the peptide (LSELRLHNN) which showed the lower binding affinity (2.3•10-4 M) to collagen. This peptide was grafted to hyaluronic acid via EDC-chemistry, with a degree of functionalization of 7 ± 2 mol\% as calculated by 1H-NMR. The grafting was further confirmed by FTIR and TGA measurements, which showed that the onset of decomposition for the HA-g-peptide decreased by 10 °C compared to the native HA. Rheological measurements showed that the elastic modulus of a system based on collagen and HA-g-peptide increased by almost two order of magnitude (G' = 200 Pa) compared to a system based on collagen and HA (G' = 0.9 Pa). Overall, this study showed that the synthetic peptides, which were identified from decorin, can be applied as potential building blocks for biomimetic materials that function via biological recognition.},
  language  = {en}
}
@phdthesis{Weiss2011,
  author    = {Weiß, Jan},
  title     = {Synthesis and self-assembly of multiple thermoresponsive amphiphilic block copolymers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53360},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.},
  language  = {en}
}
@phdthesis{Klinkusch2011,
  author    = {Klinkusch, Stefan},
  title     = {Simulations of laser-induced correlated many-electron dynamics in molecular systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55445},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In this thesis, simulations of laser-driven many-electron dynamics in molecules are presented, i.e., the interaction between molecules and an electromagnetic field is demonstrated. When a laser field is applied to a molecular system, a population of higher electronic states takes place as well as other processes, e.g. photoionization, which is described by an appropriate model. Also, a finite lifetime of an excited state can be described by such a model. In the second part, a method is postulated that is capable of describing electron correlation in a time-dependent scheme. This is done by introducing a single-electron entropy that is at least temporarily minimized in a further step.},
  language  = {en}
}
@phdthesis{tenBrummelhuis2011,
  author    = {ten Brummelhuis, Niels},
  title     = {Self-assembly of cross-linked polymer micelles into complex higher-order aggregates},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52320},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios.},
  language  = {en}
}
@phdthesis{ValverdeSerrano2011,
  author    = {Valverde Serrano, Clara},
  title     = {Self-assembly behavior in hydrophilic block copolymers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-54163},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the "less hydrophilic" barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for "the hydrophobic effect" but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the "hydrophilic effect".},
  language  = {en}
}
@phdthesis{Schumacher2011,
  author    = {Schumacher, Soeren},
  title     = {Saccharide recognition : boronic acids as receptors in polymeric networks},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52869},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {In this thesis entitled "Saccharide Recognition - Boronic acids as Receptors in Polymeric Networks" different aspects of boronic acid synthesis, their analysis and incorporation or attachment to different polymeric networks and characterisation thereof were investigated. The following key aspects were considered: • Provision of a variety of different characterised arylboronic acids and benzoboroxoles • Attachment of certain derivatives to nanoparticles and the characterisation of saccharide binding by means of isothermal titration calorimetry and displacement assay (ARS) to enhance the association constant to saccharides at pH 7.4 • Enhancement of selectivity in polymeric systems by means of molecular imprinting using fructose as template and a polymerisable benzoboroxole as functional monomer for the recognition at pH 7.4 (Joined by a diploma thesis of F. Gr{\"u}neberger) • Development of biomimetic saccharide structures and the development of saccharide (especially glucose and fructose) binding MIPs by using these structures as template molecules. In the first part of the thesis different arylboronic acid derivatives were synthesised and their binding to glucose or fructose was investigated by means of isothermal titration calorimetry (ITC). It could be derived, which is in parallel to the literature, that derivatives bearing a methylhydroxyl-group in ortho-position to the boron (benzoboroxole) exhibit in most cases a two-fold higher association constant compared to the corresponding phenylboronic acid derivative. To gain a deeper understanding NMR spectroscopy and mass spectrometry with the benzoboroxole and glucose or fructose was performed. It could be shown that the exchange rate in terms of NMR time scale is quite slow since in titration experiments new peaks appeared. Via mass spectrometry of a mixture between benzoboroxole and glucose or fructose, different binding stoichiometries could be detected showing that the binding of saccharides is comparable with their binding to phenylboronic acid. In addition, the use of Alizarin Red S as an electrochemical reporter was described for the first time to monitor the saccharide binding to arylboronic acids not only with spectroscopy. Here, the redox behaviour and the displacement were recorded by cyclic voltammograms. In the second part different applications of boronic acids in polymeric networks were investigated. The attachment of benzoboroxoles to nanoparticles was investigated and monitored by means of isothermal titration calorimetry and a colourimetric assay with Alizarin Red S as the report dye. The investigations by isothermal titration calorimetry compared the fructose binding of arylboronic acids and benzoboroxoles coupled to these nanoparticles and "free" in solution. It could be shown that the attached derivatives showed a higher binding constant due to an increasing entropy term. This states for possible multivalent binding combined with a higher water release. Since ITC could not characterise the binding of glucose to these nanoparticles due to experimental restrictions the glucose binding at pH 7.4 was shown with ARS. Here, the displacement of ARS by fructose and also glucose could be followed and consequently these nanoparticles can be used for saccharide determination. Within this investigation also the temperature stability of these nanoparticles was examined and after normal sterilisation procedures (121°C, 20 min.) the binding behaviour was still unchanged. To target the selectivity of the used polymeric networks, molecular imprinting was used as a technique for creating artificial binding pockets on a molecular scale. As functional monomer 3-methacrylamidobenzoboroxole was introduced for the recognition of fructose. In comparison to polymers prepared with vinylphenylboronic acid the benzoboroxole containing polymer had a stronger binding at pH 7.4 which was shown for the first time. In addition, another imprinted polymer was synthesised especially for the recognition of glucose and fructose employing biomimetic saccharide analogues as template molecule. The advantage to use the saccharide analogues is the defined template-functional monomer complex during the polymerisation which is not the case, for example, for glucose-boronic acid interaction. The biomimetic character was proven through structural superimposition of crystal structures of the analogues with already described crystal structures of boronic acid esters of glucose and fructose. A molecularly imprinted polymer was synthesised with vinylphenylboronic acid as the functional monomer to show that both glucose and fructose are able to bind to the polymer which was predicted by the structural similarity of the analogues. The major scientific contributions of this thesis are • the determination of binding constants for some, not yet reported saccharide - boronic acid / benzoboroxole pairs, • the use of ARS as electrochemical reporter for saccharide detection, • the thermodynamic characterisation of a saccharide binding nanoparticle system containing benzoboroxole and functioning at pH 7.4, • the use of a polymerisable benzoboroxole as functional monomer for saccharide recognition in neutral, aqueous environments • and the synthesis and utilisation of biomimetic saccharide analogues as template molecules especially for the development of a glucose binding MIP.},
  language  = {en}
}
@phdthesis{Popovic2011,
  author    = {Popovic, Jelena},
  title     = {Novel lithium iron phosphate materials for lithium-ion batteries},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-54591},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Conventional energy sources are diminishing and non-renewable, take million years to form and cause environmental degradation. In the 21st century, we have to aim at achieving sustainable, environmentally friendly and cheap energy supply by employing renewable energy technologies associated with portable energy storage devices. Lithium-ion batteries can repeatedly generate clean energy from stored materials and convert reversely electric into chemical energy. The performance of lithium-ion batteries depends intimately on the properties of their materials. Presently used battery electrodes are expensive to be produced; they offer limited energy storage possibility and are unsafe to be used in larger dimensions restraining the diversity of application, especially in hybrid electric vehicles (HEVs) and electric vehicles (EVs). This thesis presents a major progress in the development of LiFePO4 as a cathode material for lithium-ion batteries. Using simple procedure, a completely novel morphology has been synthesized (mesocrystals of LiFePO4) and excellent electrochemical behavior was recorded (nanostructured LiFePO4). The newly developed reactions for synthesis of LiFePO4 are single-step processes and are taking place in an autoclave at significantly lower temperature (200 deg. C) compared to the conventional solid-state method (multi-step and up to 800 deg. C). The use of inexpensive environmentally benign precursors offers a green manufacturing approach for a large scale production. These newly developed experimental procedures can also be extended to other phospho-olivine materials, such as LiCoPO4 and LiMnPO4. The material with the best electrochemical behavior (nanostructured LiFePO4 with carbon coating) was able to delive a stable 94\% of the theoretically known capacity.},
  language  = {en}
}
@phdthesis{Kubo2011,
  author    = {Kubo, Shiori},
  title     = {Nanostructured carbohydrate-derived carbonaceous materials},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-53157},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 - 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity. In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry. As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers). Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 \% microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 \% mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially "templated", either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range.},
  language  = {en}
}
@phdthesis{Haase2011,
  author    = {Haase, Martin F.},
  title     = {Modification of nanoparticle surfaces for emulsion stabilization and encapsulation of active molecules for anti-corrosive coatings},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55413},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {Within this work, three physicochemical methods for the hydrophobization of initially hydrophilic solid particles are investigated. The modified particles are then used for the stabilization of oil-in-water (o/w) emulsions. For all introduced methods electrostatic interactions between strongly or weakly charged groups in the system are es-sential. (i) Short chain alkylammonium bromides (C4 - C12) adsorb on oppositely charged solid particles. Macroscopic contact angle measurements of water droplets under air and hexane on flat silica surfaces in dependency of the surface charge density and alkylchain-length allow the calculation of the surface energy and give insights into the emulsification properties of solid particles modified with alkyltrimethylammonium bromides. The measure-ments show an increase of the contact angle with increasing surface charge density, due to the enhanced adsorp-tion of the oppositely charged alkylammonium bromides. Contact angles are higher for longer alkylchain lengths. The surface energy calculations show that in particular the surface-hexane or surface-air interfacial en-ergy is being lowered upon alkylammonium adsorption, while a significant increase of the surface-water interfa-cial energy occurs only at long alkyl chain lengths and high surface charge densities. (ii) The thickness and the charge density of an adsorbed weak polyelectrolyte layer (e.g. PMAA, PAH) influence the wettability of nanoparticles (e.g. alumina, silica, see Scheme 1(b)). Furthermore, the isoelectric point and the pH range of colloidal stability of particle-polyelectrolyte composites depend on the thickness of the weak polye-lectrolyte layer. Silica nanoparticles with adsorbed PAH and alumina nanoparticles with adsorbed PMAA be-come interfacially active and thus able to stabilize o/w emulsions when the degree of dissociation of the polye-lectrolyte layer is below 80 \%. The average droplet size after emulsification of dodecane in water depends on the thickness and the degree of dissociation of the adsorbed PE-layer. The visualization of the particle-stabilized o/w emulsions by cryogenic SEM shows that for colloidally stable alumina-PMAA composites the oil-water interface is covered with a closely packed monolayer of particles, while for the colloidally unstable case closely packed aggregated particles deposit on the interface. (iii) By emulsifying a mixture of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) and styrene with silica nanoparticles a highly stable o/w emulsion can be obtained in a narrow pH window. The amphoteric character of 8-HQ enables a pH dependent electrostatic interaction with silica nanoparticles, which can render them interfa-cially active. Depending on the concentration and the degree of dissociation of 8-HQ the adsorption onto silica results from electrostatic or aromatic interactions between 8-HQ and the particle-surface. At intermediate amounts of adsorbed 8-HQ the oil wettability of the particles becomes sufficient for stabilizing o/w emulsions. Cryogenic SEM visualization shows that the particles arrange then in a closely packed shell consisting of partly of aggregated domains on the droplet interface. For further increasing amounts of adsorbed 8-HQ the oil wet-tability is reduced again and the particles ability to stabilize emulsions decreases. By the addition of hexadecane to the oil phase the size of the droplets can be reduced down to 200 nm by in-creasing the silica mass fraction. Subsequent polymerization produces corrosion inhibitor filled (20 wt-\%) poly-styrene-silica composite particles. The measurement of the release of 8-hydroxyquinoline shows a rapid increase of 8-hydroxyquinoline in a stirred aqueous solution indicating the release of the total content in less than 5 min-utes. The method is extended for the encapsulation of other organic corrosion inhibitors. The silica-polymer-inhibitor composite particles are then dispersed in a water based alkyd emulsion, and the dispersion is used to coat flat aluminium substrates. After drying and cross-linking the polmer-film Confocal Laser Scanning Micros-copy is employed revealing a homogeneous distribution of the particles in the film. Electrochemical Impedance Spectroscopy in aqueous electrolyte solutions shows that films with aggregated particle domains degrade with time and don't provide long-term corrosion protection of the substrate. However, films with highly dispersed particles have high barrier properties for corrosive species. The comparison of films containing silica-polystyrene composite particles with and without 8-hydroxyquinoline shows higher electrochemical impedances when the inhibitor is present in the film. By applying the Scanning Vibrating Electrode Technique the localized corrosion rate in the fractured area of scratched polymer films containing the silica-polymer-inhibitor composite particles is studied. Electrochemical corrosion cannot be suppressed but the rate is lowered when inhibitor filled composite particles are present in the film. By depositing six polyelectrolyte layers on particle stabilized emulsion droplets their surface morphology changes significantly as shown by SEM visualization. When the oil wettability of the outer polyelectrolyte layer increases, the polyelectrolyte coated droplets can act as emulsion stabilizers themselves by attaching onto bigger oil droplets in a closely packed arrangement. In the presence of 3 mM LaCl3 8-HQ hydrophobized silica particles aggregate strongly on the oil-water inter-face. The application of an ultrasonic field can remove two dimensional shell-compartments from the droplet surface, which are then found in the aqueous bulk phase. Their size ranges up to 1/4th of the spherical particle shell.},
  language  = {en}
}