Structural features of lignin obtained at different alkaline oxidation conditions from sugarcane bagasse

Lignin is a macromolecule frequently obtained as residue during technological processing of biomass. Modifications in chemical structure of lignin generate valuable products, some with particular and unique characteristics. One of the available methods for modification of industrial lignin is oxidation by hydrogen peroxide. In this work, we conducted systematic studies of the oxidation process that were carried out at various pHs and oxidizing agent concentrations. Biophysical, biochemical, structural properties of the oxidized lignin were analyzed by UV spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy and small angle X-ray scattering. Our results reveal that lignin oxidized with 9.1% H(2)O(2) (m/v) at pH 13.3 has the highest fragmentation, oxidation degree and stability. Although this processing condition might be considered quite severe, we have concluded that the stability of the obtained oxidized lignin was greatly increased. Therefore, the identified processing conditions of oxidation may be of practical interest for industrial applications. (C) 2011 Elsevier B.V. All rights reserved.

Antioxidant Activity of Resveratrol Analogs

This study evaluated the antioxidant activity of five resveratrol analogs by relating the activity of the molecule with its chemical structure. The five resveratrol analogs were synthesized and the antioxidant activity was evaluated using the DPPH method. The resveratrol was used as the reference standard. A descriptive statistical analysis and ANOVA followed by the Tukey test, with the aid of software. The antioxidant activity of resveratrol analogs was considered statistically different, with the analog A which showed activity superior to the others. The five analogs presented lower antioxidant activity than the reference standard (p <0.001). According to the findings, hydroxylation was the molecular modification that gave the best evaluated antioxidant activity result. Resveratrol analogs may have an important antioxidative activity, but with the one with the higher IC50 was presented by the natural compound.

Influence of the base and diluent methacrylate monomers on the polymerization stress and its determinants

The aim of this study was to evaluate the effect of the association between bisphenol-A diglycidyl dimethacrylate (BisGMA) or its ethoxylated version (BisEMA) with diluents derived from the ethylene glycol dimethacrylate (EGDMA), with increasing number of ethylene glycol units (1: EGDMA, 2: DEGDMA, 3: TEGDMA, or 4: TETGDMA), or trimethylol propane trimethacrylate (TMPTMA) or 1,10-decanediol dimethacrylate (D3MA) on polymerization stress, volumetric shrinkage, degree of conversion, maximum rate of polymerization (Rpmax), and elastic modulus of experimental composites. BisGMA containing formulations presented lower shrinkage and stress but higher modulus and Rpmax than those containing BisEMA. TMPTMA presented the lowest stress among all diluents, as a result of lower conversion. EGDMA, DEGDMA, TEGDMA, and TETGDMA presented similar polymerization stress which was higher than the stress presented by D3MA and TMPTMA. D3MA presented similar conversion when copolymerized with both base monomers. The other diluents presented higher conversion when associated with BisEMA. EGDMA showed similar shrinkage compared with DEGDMA and higher than the other diluents. The lower conversion achieved by TMPTMA did not jeopardize its elastic modulus, similar to the other diluents. Despite the similar conversion presented by D3MA in comparison with EGDMA and DEGDMA, its lower elastic modulus may limit its use. Rather than proposing new materials, this study provides a systematic evaluation of off the shelf monomers and their effects on stress development, as highlighted by the analysis of conversion, shrinkage and modulus, to aid the optimization of commercially available materials. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

FTIR and SEM analysis of CO2 laser irradiated human enamel

Objectives: Considering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO2 laser by means of FTIR spectroscopy and SEM analysis. Design: The enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-mu m CO2 laser (0.55 W, 660 W/cm(2)). The carbonate absorption band at 1600-1291 cm(-1) as well as the water absorption band at 3793-2652 cm(-1) was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190-702 cm(-1)). Results: There was a statistically significant decrease (p < 0.05) in the water content after irradiation (control: 0.184 +/- 0.04; irradiated: 0.078 +/- 0.026), which increased again after rehydration (0.145 +/- 0.038). The carbonate/phosphate ratio was measured initially (0.112 +/- 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 +/- 0.014) (p < 0.05). Conclusion: The 10.6-mu m CO2 laser irradiation diminishes the carbonate and water contents in the enamel after irradiation. (C) 2012 Elsevier Ltd. All rights reserved.

Microbial transformation of the sesquiterpene lactone tagitinin C by the fungus Aspergillus terreus

The biotransformation of the sesquiterpene lactone tagitinin C by the fungus Aspergillus terreus MT 5.3 yielded a rare derivative that was elucidated by spectrometric methods. The fungus led to the formation of a different product through an unusual epoxidation reaction between C4 and C5, formation of a C3,C10 ether bridge, and a methoxylation of the C1 of tagitinin C. The chemical structure of the product, namely 1 beta-methoxy-3 alpha-hydroxy-3,10 beta-4,5 alpha-diepoxy-8 beta-isobutyroyloxygermacr-11(13)-en-6 alpha,12-olide, is the same as that of a derivative that was recently isolated from the flowers of a Brazilian population of Mexican sunflower (Tithonia diversifolia), which is the source of the substrate tagitinin C. The in vitro cytotoxic activity of the substrate and the biotransformed product were evaluated in HL-60 cells using an MTT assay, and both compounds were found to be cytotoxic. We show that soil fungi may be useful in the biotransformation of sesquiterpene lactones, thereby leading to unusual changes in their chemical structures that may preserve or alter their biological activities, and may also mimic plant biosynthetic pathways for production of secondary metabolites.

Purification and characterization of a surfactin-like molecule produced by Bacillus sp. H2O-1 and its antagonistic effect against sulfate reducing bacteria

Abstract Background Bacillus sp. H2O-1, isolated from the connate water of a Brazilian reservoir, produces an antimicrobial substance (denoted as AMS H2O-1) that is active against sulfate reducing bacteria, which are the major bacterial group responsible for biogenic souring and biocorrosion in petroleum reservoirs. Thus, the use of AMS H2O-1 for sulfate reducing bacteria control in the petroleum industry is a promising alternative to chemical biocides. However, prior to the large-scale production of AMS H2O-1 for industrial applications, its chemical structure must be elucidated. This study also analyzed the changes in the wetting properties of different surfaces conditioned with AMS H2O-1 and demonstrated the effect of AMS H2O-1 on sulfate reducing bacteria cells. Results A lipopeptide mixture from AMS H2O-1 was partially purified on a silica gel column and identified via mass spectrometry (ESI-MS). It comprises four major components that range in size from 1007 to 1049 Da. The lipid moiety contains linear and branched β-hydroxy fatty acids that range in length from C13 to C16. The peptide moiety contains seven amino acids identified as Glu-Leu-Leu-Val-Asp-Leu-Leu. Transmission electron microscopy revealed cell membrane alteration of sulfate reducing bacteria after AMS H2O-1 treatment at the minimum inhibitory concentration (5 μg/ml). Cytoplasmic electron dense inclusions were observed in treated cells but not in untreated cells. AMS H2O-1 enhanced the osmosis of sulfate reducing bacteria cells and caused the leakage of the intracellular contents. In addition, contact angle measurements indicated that different surfaces conditioned by AMS H2O-1 were less hydrophobic and more electron-donor than untreated surfaces. Conclusion AMS H2O-1 is a mixture of four surfactin-like homologues, and its biocidal activity and surfactant properties suggest that this compound may be a good candidate for sulfate reducing bacteria control. Thus, it is a potential alternative to the chemical biocides or surface coating agents currently used to prevent SRB growth in petroleum industries.

Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

NMR, Metabonomics and Molecular Profiles: Applications to the Quality Assessment of Foodstuffs

Nuclear Magnetic Resonance (NMR) is a branch of spectroscopy that is based on the fact that many atomic nuclei may be oriented by a strong magnetic field and will absorb radiofrequency radiation at characteristic frequencies. The parameters that can be measured on the resulting spectral lines (line positions, intensities, line widths, multiplicities and transients in time-dependent experi-ments) can be interpreted in terms of molecular structure, conformation, molecular motion and other rate processes. In this way, high resolution (HR) NMR allows performing qualitative and quantitative analysis of samples in solution, in order to determine the structure of molecules in solution and not only. In the past, high-field NMR spectroscopy has mainly concerned with the elucidation of chemical structure in solution, but today is emerging as a powerful exploratory tool for probing biochemical and physical processes. It represents a versatile tool for the analysis of foods. In literature many NMR studies have been reported on different type of food such as wine, olive oil, coffee, fruit juices, milk, meat, egg, starch granules, flour, etc using different NMR techniques. Traditionally, univariate analytical methods have been used to ex-plore spectroscopic data. This method is useful to measure or to se-lect a single descriptive variable from the whole spectrum and , at the end, only this variable is analyzed. This univariate methods ap-proach, applied to HR-NMR data, lead to different problems due especially to the complexity of an NMR spectrum. In fact, the lat-ter is composed of different signals belonging to different mole-cules, but it is also true that the same molecules can be represented by different signals, generally strongly correlated. The univariate methods, in this case, takes in account only one or a few variables, causing a loss of information. Thus, when dealing with complex samples like foodstuff, univariate analysis of spectra data results not enough powerful. Spectra need to be considered in their wholeness and, for analysing them, it must be taken in consideration the whole data matrix: chemometric methods are designed to treat such multivariate data. Multivariate data analysis is used for a number of distinct, differ-ent purposes and the aims can be divided into three main groups: • data description (explorative data structure modelling of any ge-neric n-dimensional data matrix, PCA for example); • regression and prediction (PLS); • classification and prediction of class belongings for new samples (LDA and PLS-DA and ECVA). The aim of this PhD thesis was to verify the possibility of identify-ing and classifying plants or foodstuffs, in different classes, based on the concerted variation in metabolite levels, detected by NMR spectra and using the multivariate data analysis as a tool to inter-pret NMR information. It is important to underline that the results obtained are useful to point out the metabolic consequences of a specific modification on foodstuffs, avoiding the use of a targeted analysis for the different metabolites. The data analysis is performed by applying chemomet-ric multivariate techniques to the NMR dataset of spectra acquired. The research work presented in this thesis is the result of a three years PhD study. This thesis reports the main results obtained from these two main activities: A1) Evaluation of a data pre-processing system in order to mini-mize unwanted sources of variations, due to different instrumental set up, manual spectra processing and to sample preparations arte-facts; A2) Application of multivariate chemiometric models in data analy-sis.

Archaeological Baltic amber: degradation mechanisms and conservation measures

The aim of this project was to achieve a deep understanding of the mechanisms by which Baltic amber degrades, in order to develop techniques for preventive conservation of archaeological amber objects belonging to the National Museum of Denmark’s collections. To examine deterioration of Baltic amber, a starting point was to identify and monitor surface and bulk properties which are affected during degradation. The way to operate consisted of the use of accelerated ageing to initiate degradation of raw Baltic amber samples in different conditions of relative humidity, oxygen exposure or pH and, successively, of the use of non/micro-destructive techniques to identify and quantify changes in visual, chemical and structural properties. A large piece of raw Baltic amber was used to prepare several test samples for two different kinds of accelerated ageing: thermal-ageing and photo-ageing. During the ageing, amber samples were regularly examined through several analytical techniques related to different information: appearance/colour change by visual examination, photography and colorimetry; chemical change by infrared spectroscopy, Raman spectroscopy and elemental analysis; rate of oxidation by oxygen measurement; qualitative analysis of released volatiles by gas chromatography – mass spectrometry. The obtained results were analysed through both critical evaluation and statistical study. After the interpretation of the achieved data, the main relations between amber and environmental factors during the degradation process became clearer and it was possible to identify the major pathways by which amber degrades, such as hydrolysis of esters into alcohols and carboxylic acids, thermal-oxidation and photo-oxidation of terpenoid components, depolymerisation and decomposition of the chemical structure. At the end it was possible to suggest a preventive conservation strategy based on the control of climatic, atmospheric and lighting parameters in the environment where Baltic amber objects are stored and displayed.

Durability of monumental stones treated with siloxane-based water repellents

The thesis investigates the effect of siloxane-based water repellents on the durability of monumental stones. Laspra, a micritic limestone typical for the Spanish region of Asturias, and Repedea, an oolitic limestone from Moldavia, Romania were selected for the present study, due to their regional / national significance and level of usage. As for the siloxane-based water repellents, three worldwide used products, namely Lotexan-N, Silres® BS 290 and Tegosivin HL 100 and a newly synthesized nanocomposite material, TMSPMA, obtained starting from the 3(trimethoxysilyl)propyl methacrylate as a precursor were investigated. The limestones and the water repellents were thoroughly characterized using specific techniques. The coating of the two monumental stones with the mentioned products and the investigation of coating efficiency yielded to the conclusion that all treatments induce good water repellent properties. The treated limestones were afterwards submitted to different artificially accelerated ageing tests – resistance against UV irradiation, resistance to salt mist action and resistance to SO2 action in the presence of humidity –, the results being analyzed according to standardized evaluation methods. The durability of the treated stones was proved to depend on both stone characteristics and water repellent chemical structure. All four water repellents induced a good protection against UV irradiation, no significant differences among them being noticed. As far as the resistance to salt mist action is concerned, the product that afforded the best results when applied on Laspra was TMSPMA, and on Repedea, Silres® BS 290 or / and TMSPMA showed the highest efficiency. The best resistance to SO2 action in the presence of humidity was conferred by Tegosivin HL 100 and TMSPMA when applied on Laspra, while Silres® BS 290 and TMSPMA afforded better results in the case of Repedea.

Derivati polimerici organometallici ancorati su matrice inorganica per applicazioni in chimica fine

Organotin compounds have found in the last few decades a wide variety of applications. Indeed, they are used successfully as antifouling paints, PVC stabilizers and ion carriers, as well as homogeneous catalysts. In this context, it has been proved that the Lewis acidity of the metal centre allows these compounds to promote the reaction between alcohol and ester. However their use is now limited by their well-known toxicity, moreover they are hardly removable from the reaction mixture. This problem can be overcome by grafting the organotin derivative onto a polymeric cross-linked support. In this way the obtained heterogeneous catalyst can be easily filtered off from the reaction mixture, thus creating the so-called "clean organotin reagents", avoiding the presence of toxic organotin residues in solution and the tin release in the environment. In the last few years several insoluble polystyrene resins containing triorganotin carboxylate moieties have been synthesized with the aim of improving their catalytic activity: in particular we have investigated and opportunely modified their chemical structure in order to optimize the accessibility to the metal centre and its Lewis acidity. Recently, we replaced the polymeric matrix with an inorganic one, in order to dispose of a relatively cheaper and easily available support. For this purpose an ordered mesoporous silica, characterized by 2D-hexagonal pores, named MCM-41, and an amorphous silica have been selected. In the present work two kinds of MCM-41 silica containing the triorganotin carboxylate moiety have been synthesized starting from a commercial Cab-O-Sil M5 silica. These catalysts have two different spacers between the core and the tin-carboxylate moiety, namely a polyaliphatic chain (compound FT29) or a poliethereal one (compound FT6), with the aim to improve the interaction between catalyst and reacting ester. Three catalysts supported onto an amorphous silica have been also synthesized: the structure is the same as silica FT29, i.e. a compound having a polialiphatic chain, and they have different percentage of organotin derivative grafted on the silica surface (10, 30, 50% respectively for silica MB9, SU27 and SU28). The performances of the above silica as heterogeneous catalysts in transesterification reactions have been tested in a model reaction between ethyl acetate and 1-octanol, a primary alcohol sensitive to the reaction conditions. The alcohol conversion was assessed by gas-chromatography, determining the relative amount of transesterified product and starting alcohol after established time intervals.

Cellulose based Lithium ion polymer electrolytes for Lithium batteries

The separator membrane in batteries and fuel cells is of crucial importance for the function of these devices. In lithium ion batteries the separator membrane as well as the polymer matrix of the electrodes consists of polymer electrolytes which are lithium ion conductors. To overcome the disadvantage of currently used polymer electrolytes which are highly swollen with liquids and thus mechanically and electrochemically unstable, the goal of this work is a new generation of solid polymer electrolytes with a rigid backbone and a soft side chain structure. Moreover the novel material should be based on cheap substrates and its synthesis should not be complicated aiming at low overall costs. The new materials are based on hydroxypropylcellulose and oligoethyleneoxide derivatives as starting materials. The grafting of the oligoethyleneoxide side chains onto the cellulose was carried out following two synthetic methods. One is based on a bromide derivative and another based on p-toluolsulfonyl as a leaving group. The side chain reagents were prepared form tri(ethylene glycol) monoethyl ether. In order to improve the mechanical properties the materials were crosslinked. Two different conceptions have been engaged based on either urethane chemistry or photosensitive dimethyl-maleinimide derivatives. PEO - graft - cellulose derivatives with a high degree of substitution between 2,9 and 3,0 were blended with lithium trifluoromethane-sulfonate, lithium bis(trifluorosulfone)imide and lithium tetrafluoroborate. The molar ratios were in the range from 0,02 to 0,2 [Li]/[O]. The products have been characterized with nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and laserlight scattering (LS) with respect to their degree of substitution and molecular weight. The effect of salt concentration on ionic conductivity, thermal behaviour and morphology has been investiga-ted with impedance spectroscopy, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The crosslinking reactions were controlled with dynamic mechanical analysis (DMS). The degree of substitution of our products is varying between 2,8 and 3,0 as determined by NMR. PEO - graft - cellulose derivatives are highly viscous liquids at room temperature with glass transition temperatures around 215 K. The glass transition temperature for the Lithium salt complexes of PEO - graft - cellulose deri-vatives increase with increasing salt content. The maximum conductivity at room temperature is about 10-4 and at 100°C around 10-3 Scm-1. The presence of lithium salt decreases the thermal stability of the complexes in comparison to pure PEO - graft - cellulose derivatives. Complexes heated over 140 – 150°C completely lose their ionic conductivity. The temperature dependence of the conductivity presented as Arrhenius-type plots for all samples is similar in shape and follows a VTF behaviour. This proofs that the ionic transport is closely related to the segmental motions of the polymer chains. Novel cellulose derivatives with grafted oligoethylen-oxide side chains with well-defined chemical structure and high side chain grafting density have been synthesized. Cellulose was chosen as stiff, rod like macromolecule for the backbone while oligoethylen-oxides are chosen as flexible side chains. A maximum grafting density of 3.0 have been obtained. The best conductivity reaches 10-3 Scm-1 at 100°C for a Li-triflate salt complex with a [Li]/[O] ratio of 0.8. The cross-linked complexes containing the lithium salts form elastomeric films with convenient mechanical stability. Our method of cellulose modification is based on relatively cheap and commercially available substrates and as such appears to be a promising alternative for industrial applications.

Synthese von amphiphilen Bürstenpolymeren mit Kern-Schale-Architektur und Untersuchungen zur Verkapselung von hydrophilen Modellsubstanzen

Die dieser Arbeit zugrundeliegenden Nanopartikel wurden mittels der Makromonomer-Strategie aus polymerisierbaren Polystyrol-b-Poly(2-vinylpyridin) Oligomeren dargestellt. Die Bürstenpolymere besitzen eine polare PS-Schale und einen polaren Kern (P2VP), dessen Polarität durch Quaternisierung deutlich erhöht werden kann. Die Bürstenpolymere weisen bei Molmassen um 400 - 800 kg/mol einen Teilchendurchmesser von ca. 15 - 20 nm auf. Die Nanopartikel eignen sich dazu, hydrophile Farbstoffe in unpolaren Lösungsmitteln zu solubilisieren. Durch spektroskopische Untersuchungen wurden in Abhängigkeit der chemischen Struktur und der Bürstenpolymere Beladungsgrade von über 1 g Farbstoff pro Gramm Polymer ermittelt. Die Beladung der Nanopartikel folgt hierbei einer nichttrivialen Kinetik, was möglicherweise durch eine wasserinduzierte Überstrukturbildung während der Beladung bedingt ist. Mittels isothermer Titrationskalorimetrie konnten die Wechselwirkungen zwischen polymeren Substrat und niedermolekularen Liganden genauer charakterisiert werden. Teilweise werden hierbei zweistufige Titrationsverläufe und "überstöchiometrische" Beladung der Bürstenpolymere beobachtet. Den Hauptbeitrag zur Wechselwirkung liefert hierbei die exotherme Wechselwirkung zwischen basischen Polymer und saurem Farbstoff. Die hohe Farbstoffbeladung führt zur deutlichen Vergrößerung der einzelnen Nanopartikel, was sowohl in Lösung durch Lichtstreu-Techniken als auch auf Oberflächen mit Hilfe des AFM zu beobachten ist. Durch Untersuchungen mit der analytischen Ultrazentrifuge konnte nachgewiesen werden, dass sich der eingelagerte Farbstoff in einem Polaritäts-abhängigen Gleichgewicht mit der Umgebung steht, er somit auch wieder aus den Nanopartikeln freigesetzt werden kann. Darüberhinaus wurden im Rahmen der Arbeit erste Erfolge bei der Synthese von wasserlöslichen Nanopartikeln mit Poly(2-vinylpyridin)-Kern erzielt. Als hierfür geeignet stellte sich eine Synthesestrategie heraus, bei der zunächst ein Bürstenpolymer mit P2VP-Seitenketten dargestellt und dieses anschließend mit geeignet funktionalisierten Polyethylenoxid-Ketten zum Kern-Schale Teilchen umgesetzt wurde. Neben Untersuchungen zum Mizellisierungsverhalten von PEO-b-P2VP Makromonomeren wurden deren Aggregate in Wasser hinsichtlich ihrer Zelltoxizität durch in-vitro Experimente an C26-Mäusekarzinom-Zellen charakterisiert. Die extrem geringe Toxizität macht das PEO-P2VP System zu einem potentiellen Kandidaten für drug-delivery Anwendungen. Besonders die pH-abhängige Löslichkeitsänderung des Poly(2-vinylpyridin) erscheint hierbei besonders interessant.

Charakterisierung von plasmafunktionalisierten Oberflächen mittels ToF-SIMS und multivariaten Analysemethoden

Die grundlegenden Prinzipien und Möglichkeiten der Oberflächencharakterisierung mittels ToF-SIMS (Flugzeit-Sekundärionen Massenspektrometrie) werden an ausgewählten Beispielen aus einem aktuell laufenden und vom BMBF geförderten Verbundforschungsprojekt (Fkz: 03N8022A) zum Thema Nanofunktionalisierung von Grenzflächen vorgestellt. Ein Schwerpunkt innerhalb des Projekts stellen die nichtgeschlossenen Schichtsysteme dar, die entweder über Domänenstrukturen oder einer definierten Einzelfunktionalisierung neuartige funktionelle Oberflächen bereitstellen. Mithilfe der sehr oberflächensensitiven ToF-SIMS Methode sowie der Möglichkeit einer graphischen Darstellung lateraler Molekülionenverteilungen auf funktionalisierten Oberflächen können Informationen über Struktur und Belegungsdichte der Funktionsschicht gewonnen werden. Die Kombination des ToF-SIMS Experimentes und eines multivariaten Algorithmus (partial least squares, PLS) liefert eine interessante Möglichkeit zur quantitativen und simultanen Bestimmung von Oberflächeneigenschaften (Element- und molekulare Konzentrationen sowie Kontaktwinkelwerte). Da das ToF-SIMS Spektrum einer plasmafunktionalisierten Oberfläche im Allgemeinen eine Vielzahl unterschiedlicher Fragmentsignale enthält, lässt eine einfache eindimensionale Korrelation (z.B. CF3 - Fragmentintensität ßà CF3-Konzentration) den größten Teil der im Spektrum prinzipiell enthaltenen Information unberücksichtigt. Aufgrund der großen Anzahl von atomaren und molekularen Signalen, die repräsentativ für die chemische Struktur der analysierten Oberflächen sind, ist es sinnvoll, diese Fülle von Informationen zur Quantifizierung der Oberflächeneigenschaften (Elementkonzentrationen, Kontaktwinkel etc.) zu verwenden. Zusätzlich ermöglicht diese Methode eine quantitative Bestimmung der Oberflächeneigenschaften auf nur µm-großen Bereichen. Das ist vorteilhaft für Untersuchungen chemisch strukturierter Oberflächen, da die Größe der Strukturierung für viele Anwendungen in einem Bereich von mehreren µm liegt. Anhand eines Beispieles aus dem biologisch-medizinischen Fachgebiet, soll der erfolgreiche Einsatz multivariater Modelle aufgezeigt werden. In diesem Experiment wurden menschlichen Bindegewebs- (Fibroblasten) und Pankreaszellen auf plasmafunktionalisiserten Oberflächen kultiviert, um die Beeinflussung der Funktionalisierung auf das Zellwachstum zu untersuchen. Die plasmabehandelten Oberflächen wurden durch die Verwendung von TEM-Gittern mit µm-großen Öffnungen chemisch strukturiert und das Wachstumsverhalten der Zellen beobachtet. Jedem dieser µm-großen Bereiche können mithilfe der multivariaten Modelle quantitative Größen zugeordnet werden (Konzentrationen und Kontaktwinkelwerte), die zur Interpretation des Wachstumsverhaltens der Zellen beitragen.

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.