Improving Planting Stocks for the Brazilian Atlantic Forest Restoration through Community-Based Seed Harvesting Strategies

High-diversity reforestation can help jumpstart tropical forest restoration, but obtaining viable seedlings is a major constraint: if nurseries do not offer them, it is hard to plant all the species one would like. From 2007 to 2009, we investigated five different seed acquisition strategies employed by a well-established tree nursery in southeastern Brazil, namely (1) in-house seed harvesters; (2) hiring a professional harvester; (3) amateur seed harvesters; or (4) a seed production cooperative, as well as (5) participating in a seed exchange program. In addition, we evaluated two strategies not dependent on seeds: harvesting seedlings from native tree species found regenerating under Eucalyptus plantations, and in a native forest remnant. A total of 344 native tree and shrub species were collected as seeds or seedlings, including 2,465 seed lots. Among these, a subset of 120 species was obtained through seed harvesting in each year. Overall, combining several strategies for obtaining planting stocks was an effective way to increase species richness, representation of some functional groups (dispersal syndromes, planting group, and shade tolerance), and genetic diversity of seedlings produced in forest tree nurseries. Such outcomes are greatly desirable to support high-diversity reforestation as part of tropical forest restoration. In addition, community-based seed harvesting strategies fostered greater socioeconomic integration of traditional communities in restoration projects and programs, which is an important bottleneck for the advance of ecological restoration, especially in developing countries. Finally, we discuss some of the limitations of the various strategies for obtaining planting stocks and the way forward for their improvement.

Soil-nutrient availability modifies the response of young pioneer and late successional trees to elevated carbon dioxide in a Brazilian tropical environment

The aim of this work was to determine the impact of three levels of [CO2] and two levels of soil-nutrient availability on the growth and physiological responses of two tropical tree species differing in their ecological group: Croton urucurana Baillon, a pioneer (P), and also Cariniana legalis (Martius) Kuntze, a late succession (LS). We aimed to test the hypothesis that P species have stronger response to elevated [CO2] than LS species as a result of differences in photosynthetic capacity and growth kinetics between both functional groups. Seedlings of both species were grown in open-top-chambers under high (HN) or low (LN) soil-nutrient supply and exposed to ambient (380 mu mol mol(-1)) or elevated (570 and 760 mu mol mol(-1)) [CO2]. Measurements of gas exchange, chlorophyll a fluorescence, seedling biomass and allocation were made after 70 days of treatment. Results suggest that elevated [CO2] significantly enhances the photosynthetic rates (A) and biomass production in the seedlings of both species, but that soil-nutrient supply has the potential to modify the response of young tropical trees to elevated [CO2]. In relation to plants grown in ambient [CO2], the P species grown under 760 mu mol mol(-1) [CO2] showed increases of 28% and 91% in A when grown in LN and HN, respectively. In P species grown under 570 mu mol mol(-1) [CO2], A increased by 16% under HN, but there was no effect in LN. In LS species, the enhancement of A by effect of 760 mu mol mol(-1) [CO2] was 30% and 70% in LN and HN, respectively. The exposure to 570 mu mol mol(-1) [CO2] stimulated A by 31% in HN, but was no effect in LN. Reductions in stomatal conductance (g(s)) and transpiration (E), as a result of elevated [CO2] were observed. Increasing the nutrient supply from low to high increased both the maximum rate of carboxylation (V-cmax) and maximum potential rate of electron transport (J(max)). As the level of [CO2] increased, both the V-cmax and the J(max) were found to decrease, whereas the J(max)/V-cmax ratio increased. In the LS species, the maximum efficiency of PSII (F-v/F-m) was higher in the 760 mu mol mol(-1) [CO2] treatment relative to other [CO2] treatments. The results suggest that when grown under HN and the highest [CO2], the performance of the P species C. urucurana, in terms of photosynthesis and biomass enhancement, is better than the LS species C. legalis. However, a larger biomass is allocated to roots when C. legalis seedlings were exposed to elevated [CO2]. This response would be an important strategy for plant survival and productivity of the LS species under drought stresses conditions on tropical environments in a global-change scenario. (C) 2011 Elsevier B.V. All rights reserved.

Electronics and Optics of Graphene Nanoflakes: Edge Functionalization and Structural Distortions

The effects of edge covalent functionalization on the structural, electronic, and optical properties of elongated armchair graphene nanoflakes (AGNFs) are analyzed in detail for a wide range of terminations, within the framework of Hartree-Fock-based semiempirical methods. The chemical features of the functional groups, their distribution, and the resulting system symmetry are identified as the key factors that determine the modification of strutural and optoelectronic features. While the electronic gap is always reduced in the presence of substituents, functionalization-induced distortions contribute to the observed lowering by about 35-55% This effect is paired with a red shift of the first optical peak, corresponding to about 75% of the total optical gap reduction. Further, the functionalization pattern and the specific features of the edge-substituent bond are found to influence the strength and the character of the low-energy excitations. All of these effects are discussed for flakes of different widths, representing the three families of AGNFs.

Database of diazotrophs in global ocean: abundances, biomass and nitrogen fixation rates

[EN] Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems 5 and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR 10 assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert  abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. 15 Lower mean N2 fixation rate was found in the North Atlantic Ocean than the Pacific Ocean. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (53–73) TgNyr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 4.7 (2.3–9.6) TgC from cell counts and to 89 (40–20 200) TgC from nifH-based abundances. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70 %. This evolving database can be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models. The database is 25 stored in PANGAEA (http://doi.pangaea.de/10.1594/PANGAEA.774851).

The structure of planktonic communities under variable coastal upwelling conditions off Cape Ghir (31ºN), in the Canary Current System (NW Africa)

Universidad de Las Palmas de Gran Canaria. Facultad de Ciencias del Mar. Programa de doctorado en Oceanografía. Diploma de Estudios Avanzados

Optically active photoresponsive multifunctional polymeric materials

In the last year [1], Angiolini and co-workers have synthesized and investigated methacrylic polymers bearing in the side chain the chiral cyclic (S)-3-hydroxypyrrolidine moiety interposed between the main chain and the trans-azoaromatic chromophore, substituted or not in the 4’ position by an electron-withdrawing group. In these materials, the presence of a rigid chiral moiety of one prevailing absolute configuration favours the establishment of a chiral conformation of one prevailing helical handedness, at least within chain segments of the macromolecules, which can be observed by circular dichroism (CD). The simultaneous presence of the azoaromatic and chiral functionalities allows the polymers to display both the properties typical of dissymmetric systems (optical activity, exciton splitting of dichroic absorptions), as well as the features typical of photochromic materials (photorefractivity, photoresponsiveness, NLO properties). The first part of this research was to synthesize analogue homopolymers and copolymers based on bisazoaromatic moiety and compare their properties to those of the above mentioned analogue derivatives bearing only one azoaromatic chromophore in the side chain. We focused also the attention on the effects induced on the thermal and chiroptical behaviours by the insertion of particulars achiral comonomers characterized by different side-chain mobility and grown hindrance (MMA, tert-BMA and TrMA). On the other hand carbazole containing polymers [2] have attracted much attention because of their unique features. The use of these materials in advanced micro- and nanotechnologies spreads in many different applications such as photoconductive and photorefractive polymers, electroluminescent devices, programmable optical interconnections, data storage, chemical photoreceptors, NLO, surface relief gratings, blue emitting materials and holographic memory. The second part of the work was focused on the synthesis and the characterization polymeric derivatives bearing in the side chain carbazole or phenylcarbazole moieties linked to the (S)- 2-hydroxy succinimide or the (S)-3-hydroxy pyrrolidinyl ring as chiral groups covalently linked to the main chain through ester bonds. The last objective of this research was to design, synthesize, and characterize multifunctional methacrylic homopolymers and copolymers bearing three distinct functional groups (i.e. azoaromatic, carbazole and chiral group of one single configuration) directly linked in the side chain. This polymeric derivatives could be of potential interest for several advanced application fields, such as optical storage, waveguides, chiroptical switches, chemical photoreceptors, NLO, surface relief gratings, photoconductive materials, etc.

De Novo Design of secondary structures: Synthesis and conformational studies

Chemists have long sought to extrapolate the power of biological catalysis and recognition to synthetic systems. These efforts have focused largely on low molecular weight catalysts and receptors; however, biological systems themselves rely almost exclusively on polymers, proteins and RNA, to perform complex chemical functions. Proteins and RNA are unique in their ability to adopt compact, well-ordered conformations, and specific folding provides precise spatial orientation of the functional groups that comprise the “active site”. These features suggest that identification of new polymer backbones with discrete and predictable folding propensities (“foldamers”) will provide a basis for design of molecular machines with unique capabilities. The foldamer approach complements current efforts to design unnatural properties into polypeptides and polynucleotides. The aim of this thesis is the synthesis and conformational studies of new classes of foldamers, using a peptidomimetic approach. Moreover their attitude to be utilized as ionophores, catalysts, and nanobiomaterials were analyzed in solution and in the solid state. This thesis is divided in thematically chapters that are reported below. It begins with a very general introduction (page 4) which is useful, but not strictly necessary, to the expert reader. It is worth mentioning that paragraph I.3 (page 22) is the starting point of this work and paragraph I.5 (page 32) isrequired to better understand the results of chapters 4 and 5. In chapter 1 (page 39) is reported the synthesis and conformational analysis of a novel class of foldamers containing (S)-β3-homophenylglycine [(S)-β3-hPhg] and D- 4-carboxy-oxazolidin-2-one (D-Oxd) residues in alternate order is reported. The experimental conformational analysis performed in solution by IR, 1HNMR, and CD spectroscopy unambiguously proved that these oligomers fold into ordered structures with increasing sequence length. Theoretical calculations employing ab initio MO theory suggest a helix with 11-membered hydrogenbonded rings as the preferred secondary structure type. The novel structures enrich the field of peptidic foldamers and might be useful in the mimicry of native peptides. In chapter 2 cyclo-(L-Ala-D-Oxd)3 and cyclo-(L-Ala-DOxd) 4 were prepared in the liquid phase with good overall yields and were utilized for bivalent ions chelation (Ca2+, Mg2+, Cu2+, Zn2+ and Hg2+); their chelation skill was analyzed with ESI-MS, CD and 1HNMR techniques and the best results were obtained with cyclo-(L-Ala-D-Oxd)3 and Mg2+ or Ca2+. Chapter 3 describes an application of oligopeptides as catalysts for aldol reactions. Paragraph 3.1 concerns the use of prolinamides as catalysts of the cross aldol addition of hydroxyacetone to aromatic aldeydes, whereas paragraphs 3.2 and 3.3 are about the catalyzed aldol addition of acetone to isatins. By means of DFT and AIM calculations, the steric and stereoelectronic effects that control the enantioselectivity in the cross-aldol addition of acetone to isatin catalysed by L-proline have been studied, also in the presence of small quantities of water. In chapter 4 is reported the synthesis and the analysis of a new fiber-like material, obtained from the selfaggregation of the dipeptide Boc-L-Phe-D-Oxd-OBn, which spontaneously forms uniform fibers consisting of parallel infinite linear chains arising from singleintermolecular N-H···O=C hydrogen bonds. This is the absolute borderline case of a parallel β-sheet structure. Longer oligomers of the same series with general formula Boc-(L-Phe-D-Oxd)n-OBn (where n = 2-5), are described in chapter 5. Their properties in solution and in the solid state were analyzed, in correlation with their attitude to form intramolecular hydrogen bond. In chapter 6 is reported the synthesis of imidazolidin-2- one-4-carboxylate and (tetrahydro)-pyrimidin-2-one-5- carboxylate, via an efficient modification of the Hofmann rearrangement. The reaction affords the desired compounds from protected asparagine or glutamine in good to high yield, using PhI(OAc)2 as source of iodine(III).

Effect of multiple sources of disturbance on rocky benthic assemblages in some localities of Salento, Apulia

The first part of my work consisted in samplings conduced in nine different localities of the salento peninsula and Apulia (Italy): Costa Merlata (BR), Punta Penne (BR), Santa Cesarea terme (LE), Santa Caterina (LE), Torre Inserraglio (LE), Torre Guaceto (BR), Porto Cesareo (LE), Otranto (LE), Isole Tremiti (FG). I collected data of species percentage covering from the infralittoral rocky zone, using squares of 50x50 cm. We considered 3 sites for location and 10 replicates for each site, which has been taken randomly. Then I took other data about the same places, collected in some years, and I combined them together, to do a spatial analysis. So I started from a data set of 1896 samples but I decided not to consider time as a factor because I have reason to think that in this period of time anthropogenic stressors and their effects (if present), didn’t change considerably. The response variable I’ve analysed is the covering percentage of an amount of 243 species (subsequently merged into 32 functional groups), including seaweeds, invertebrates, sediment and rock. 2 After the sampling, I have been spent a period of two months at the Hopkins Marine Station of Stanford University, in Monterey (California,USA), at Fiorenza Micheli's laboratory. I've been carried out statistical analysis on my data set, using the software PRIMER 6. My explorative analysis starts with a nMDS in PRIMER 6, considering the original data matrix without, for the moment, the effect of stressors. What comes out is a good separation between localities and it confirms the result of ANOSIM analysis conduced on the original data matrix. What is possible to ensure is that there is not a separation led by a geographic pattern, but there should be something else that leads the differences. Is clear the presence of at least three groups: one composed by Porto cesareo, Torre Guaceto and Isole tremiti (the only marine protected areas considered in this work); another one by Otranto, and the last one by the rest of little, impacted localities. Inside the localities that include MPA(Marine Protected Areas), is also possible to observe a sort of grouping between protected and controlled areas. What comes out from SIMPER analysis is that the most of the species involved in leading differences between populations are not rare species, like: Cystoseira spp., Mytilus sp. and ECR. Moreover I assigned discrete values (0,1,2) of each stressor to all the sites I considered, in relation to the intensity with which the anthropogenic factor affect the localities. 3 Then I tried to estabilish if there were some significant interactions between stressors: by using Spearman rank correlation and Spearman tables of significance, and taking into account 17 grades of freedom, the outcome shows some significant stressors interactions. Then I built a nMDS considering the stressors as response variable. The result was positive: localities are well separeted by stressors. Consequently I related the matrix with 'localities and species' with the 'localities and stressors' one. Stressors combination explains with a good significance level the variability inside my populations. I tried with all the possible data transformations (none, square root, fourth root, log (X+1), P/A), but the fourth root seemed to be the best one, with the highest level of significativity, meaning that also rare species can influence the result. The challenge will be to characterize better which kind of stressors (including also natural ones), act on the ecosystem; and give them a quantitative and more accurate values, trying to understand how they interact (in an additive or non-additive way).

Mass transport in polymers

The study of mass transport in polymeric membranes has grown in importance due to its potential application in many processes such as separation of gases and vapors, packaging, controlled drug release. The diffusion of a low molecular weight species in a polymer is often accompanied by other phenomena like swelling, reactions, stresses, that have not been investigated in all their aspects yet. Furthermore, novel materials have been developed that include inorganic fillers, reactive functional groups or ions, that make the scenery even more complicated. The present work focused on the experimental study of systems where the diffusion is accompanied by other processes; suitable models were also developed to describe the particular circumstances in order to understand the underlying concepts and be able to design the performances of the material. The effect of solvent-induced deformation in polymeric films during sorption processes was studied since the dilation, especially in constrained membranes, can cause the development of stresses and therefore early failures of the material. The bending beam technique was used to test the effects of the dilation and the stress induced in the polymer by penetrant diffusion. A model based on the laminate theory was developed that accounts for the swelling and is able to predict the stress that raise in the material. The addition of inorganic fillers affects the transport properties of polymeric films. Mixed matrix membranes based on fluorinated, high free volume matrices show attractive performances for separation purposes but there is a need for deeper investigation of the selectivity properties towards gases and vapors. A new procedure based on the NELF model was tested on the experimental data; it allows to predict solubility of every penetrant on the basis of data for one vapor. The method has proved to be useful also for the determination of the diffusion coefficient and for an estimation of the permeability in the composite materials. Oxygen scavenging systems can overcome lack of barrier properties in common polymers that forbids their application in sensitive applications as food packaging. The final goal of obtaining a membrane almost impermeable to oxygen leads to experimental times out of reach. Hence, a simple model was developed in order to describe the transport of oxygen in a membrane with also reactive groups and analyze the experimental data collected on SBS copolymers that show attractive scavenging capacity. Furthermore, a model for predicting the oxygen barrier behavior of a film formed as a blend of OSP in a common packaging material was built, considering particles capable of reactions with oxygen embedded in a non-reactive matrix. Perfluorosulphonic acid ionomers (PFSI) are capturing attention due to a high thermal and chemical resistance coupled with very peculiar transport properties, that make them appropriate to be used in fuel cells. The possible effect of different formation procedure was studied together with the swelling due to water sorption since both water uptake and dilation can dramatically affect the fuel cells performances. The water diffusion and sorption was studied with a FTIR-ATR spectrometer that can give deeper information on the bonds between water molecules and the sulphonic hydrophilic groups and, therefore, on the microstructure of the hydrated ionomer.

Charakterisierung und Funktionalisierung von Polyphenylen-Dendrimeren

Die vorliegende Arbeit beschäftigt sich mit der Synthese, Funktionalisierung und Charakterisierung hochverzweigter Polyphenylen-Dendrimere. Dendrimere sind sternförmig aufgebaute Makromoleküle mit regelmäßig verzweigten Armen. Trotz der Herstellung einer Vielfalt von unterschiedlichen Dendrimertypen bleibt die Herstellung steifer formpersistenter nanometergroßer Dendrimere eine Herausforderung. Ein Ansatz zur Herstellung von form- und größenstabilen 'Nanoobjekten' wird in dieser Arbeit vorgestellt. Grundlage der Synthese der in dieser Arbeit hergestellten Polyphenylen-Dendrimere ist die Diels-Alder-Cycloaddition zwischen Tetraphenylcyclopentadienonen und Ethinylderivaten. Auf diese Weise können monodisperse Makromoleküle mit Molekularmassen größer 20 kDa und Durchmessern von 6 nm erhalten werden. Funktionalisiert werden die Dendrimere mit Funktionen wie z. B. Alkyl, Hydroxy oder Carboxy. Die Charakterisierung erfolgt u. a. mit Hilfe der NMR, GPC, Lichtstreuung oder MALDI-TOF Massenspektrometrie, aber auch mit abbildenden Methoden, wie z. B. der AFM und TEM und der Kristallstrukturanalyse. Die Dynamik der vorgestellten Dendrimere wird zum einen mit molekulardynamischen Berechnungen, zum anderen mit der Festkörper-NMR untersucht.Die Ergebnisse der Untersuchungen beweisen, dass Polyphenylen-Dendrimere nanometergroße steife formstabile Moleküle sind. Sie besitzen in erster Näherung eine globuläre Form, die große Hohlräume enthalten, in die Gastmoleküle eindringen können. Weiterhin erlauben sie eine bezüglich der Anzahl und Position definierte Funktionalisierung.

Formtreue organische Makrocyclen mit polarem Innenraum

Zusammenfassung Die Arbeit beschreibt die Synthese und Eigenschaften von formtreuen organischen Makrocyclen mit intraannularen polaren Gruppen. Dabei wurden zunächst entsprechende bifunktionalisierte Acetylenbausteine (Halbringe) hergestellt, welche anschließend in einer oxidativen Glaser-Eglington Kupplung zu den Makrocyclen umgesetzt wurden.Am Anfang wurden Sulfonat-funktionalisierte Makrocyclen untersucht. Diese ließen sich mittels der Templatmethode in hohen Ausbeuten synthetisieren. Nach der Abspaltung des Templatbausteins, der gleichzeitig als Schutzgruppe für die Sulfonsäure diente, erhielt man den entsprechenden Makrocyclus als Tetra-n-butylammonium-Salz. Vor dem Hintergrund ionenleitfähige Materialien zu erhalten, wurde anschließend das organische Kation durch anorganische Kationen (z.B. Li+, Na+) ausgetauscht. Dies führte jedoch zur Bildung unlöslicher Produkte, die sich nicht eindeutig charakterisierten ließen.Ein anderer Ansatz zu löslichen Makrocyclen mit polarem Innenraum zu gelangen war die Synthese eines Dipeptid-funktionalisierten Makrocyclus. Dies geschah im Hinblick auf die eventuelle Eignung der Makrocyclen als Rezeptormoleküle für Gäste biologischen Ursprungs. Dabei ließen sich die entsprechenden Dipeptid-funktionalisierten Halbringe auf einfache Weise darstellen, jedoch trat bei der anschließenden Glaser-Kupplung, wahrscheinlich bedingt durch den hohen molaren Überschuß an Kupfersalzen, als Hauptreaktion die Abspaltung des Peptidrests auf. Daher wurde sich nun der Carbonsäuregruppe als polaren Baustein im Inneren der Ringe zugewandt. Diese sollten eine anschließende Peptidankupplung zulassen.Es wurden vier verschiedene Makrocyclen mit intraannularen Carboxylatgruppen synthetisiert. Auch hier waren die Makrocyclen in Form ihrer Methylester noch gut, in Form der Säuren oder deren Salze oftmals nur noch sehr gering löslich. Um die Löslichkeit zu verbessern, wurde dabei die Polaritätsverteilung am Ring (polarer Innenraum, unpolarer Außenraum) durch das Anbringen von löslichkeits-vermittelnden Gruppen zum Teil aufgegeben. Dabei hat sich gezeigt, daß es erst durch die Verwendung von verzweigten (S)-Methylbutoxy-Gruppen innerhalb des Rings oder langen Alkoxyketten außerhalb des Rings möglich war, zu löslichen Systemen zu gelangen. Im ersten Fall ist es zum ersten Mal gelungen, einen löslichen Makrocyclus mit zwei freien intra-annnularen Carbonsäuregruppen zu erhalten. Durch die Optimierung der Syntheseroute ist es nunmehr möglich, den Ring im Grammmaßstab herzustellen. Außerdem wurden als Testreaktion beide Säuregruppen mit Methylamin zum Säureamid vollständig umgesetzt. Somit wurde ein System entwickelt, an das sich in Zukunft beliebige Aminosäuren an den Ring anbinden lassen sollten. Zusätzlich sollte sich die Chiralität der (S)-Methylbutoxygruppen auf das Erkennen von chiralen Gästen auswirken.Im zweiten Fall wurden durch das Anbringen von vier Tris(hexadecyloxy)-benzol- oder Tris(dodecyloxy)-benzol- Gruppen an der Peripherie der Ringe nach Hydrolyse der Methylestergruppen ebenfalls lösliche, Carboxylat-funktionalisierte Makrocyclen erhalten. Eine eingehende Untersuchung der Methylester-geschützten Ringe ergab, daß diese beim Schmelzen das Auftreten einer thermotropen flüssigkristallinen Phase zeigen. Die Natur der Mesophase konnte mittels Polarisations-Lichtmikroskopie sowie Röntgenbeugungsmethoden eindeutig als kolumnar-schiefwinklig (colob) charakterisiert werden. Hierbei ist zu bemerken, daß bei ähnlichen Makrocyclen, die über keinen polar gefüllten Innenraum verfügen, keine Mesophase auftritt. Das bedeutet, daß die Raumerfüllung im Inneren der Makrocyclen, bedingt durch die polaren Gruppen, zur Ausbildung einer flüssigkristallinen Phase unbedingt notwendig ist.

Synthesis and characterisation of photoreactive silanes for the self-assembly on functionalised silica surfaces

The aim of this thesis was to investigate novel techniques to create complex hierarchical chemical patterns on silica surfaces with micro to nanometer sized features. These surfaces were used for a site-selective assembly of colloidal particles and oligonucleotides. To do so, functionalised alkoxysilanes (commercial and synthesised ones) were deposited onto planar silica surfaces. The functional groups can form reversible attractive interactions with the complementary surface layers of the opposing objects that need to be assembled. These interactions determine the final location and density of the objects onto the surface. Photolithographically patterned silica surfaces were modified with commercial silanes, in order to create hydrophilic and hydrophobic regions on the surface. Assembly of hydrophobic silica particles onto these surfaces was investigated and finally, pH and charge effects on the colloidal assembly were analysed. In the second part of this thesis the concept of novel, "smart" alkoxysilanes is introduced that allows parallel surface activation and patterning in a one-step irradiation process. These novel species bear a photoreactive head-group in a protected form. Surface layers made from these molecules can be irradiated through a mask to remove the protecting group from selected regions and thus generate lateral chemical patterns of active and inert regions on the substrate. The synthesis of an azide-reactive alkoxysilane was successfully accomplished. Silanisation conditions were carefully optimised as to guarantee a smooth surface layer, without formation of micellar clusters. NMR and DLS experiments corroborated the absence of clusters when using neither water nor NaOH as catalysts during hydrolysis, but only the organic solvent itself. Upon irradiation of the azide layer, the resulting nitrene may undergo a variety of reactions depending on the irradiation conditions. Contact angle measurements demonstrated that the irradiated surfaces were more hydrophilic than the non-irradiated azide layer and therefore the formation of an amine upon irradiation was postulated. Successful photoactivation could be demonstrated using condensation patterns, which showed a change in wettability on the wafer surface upon irradiation. Colloidal deposition with COOH functionalised particles further underlined the formation of more hydrophilic species. Orthogonal photoreactive silanes are described in the third part of this thesis. The advantage of orthogonal photosensitive silanes is the possibility of having a coexistence of chemical functionalities homogeneously distributed in the same layer, by using appropriate protecting groups. For this purpose, a 3',5'-dimethoxybenzoin protected carboxylic acid silane was successfully synthesised and the kinetics of its hydrolysis and condensation in solution were analysed in order to optimise the silanisation conditions. This compound was used together with a nitroveratryl protected amino silane to obtain bicomponent surface layers. The optimum conditions for an orthogonal deprotection of surfaces modified with this two groups were determined. A 2-step deprotection process through a mask generated a complex pattern on the substrate by activating two different chemistries at different sites. This was demonstrated by colloidal adsorption and fluorescence labelling of the resulting substrates. Moreover, two different single stranded oligodeoxynucleotides were immobilised onto the two different activated areas and then hybrid captured with their respective complementary, fluorescent labelled strand. Selective hybridisation could be shown, although non-selective adsorption issues need to be resolved, making this technique attractive for possible DNA microarrays.

Nanosized polymer carriers for metallocene catalysts in heterogeneous olefin polymerization

Das Ziel der vorgelegten Arbeit war die Synthese von definierten, sphärischen Polystyrolpartikeln im Größenbreichen von Nanometern, die als Träger für die Immobilisierung von Metallocenkatalysatoren verwendet werden sollten. Ein wichtiger Anspruch an das System war dabei die Möglichkeit einer homogene Verteilung des Metallocenes auf dem Träger and eine homogene Fragmentierung des geträgerten Katalysators während der Polymerisation im Polymerprodukt. Für diese Zielsetzung wurden unterschiedliche Polystyrolnanopartikel hergestellt. Die Polystyrolnanopartikel waren mit unterschiedlichen funktionellen Gruppen wie Polyethylenoxid- und Polypropylenoxidketten oder Hydroxygruppen auf der Oberfläche versehen, um den Metallocenkatalysator und den Cokatalysator MAO immobilisieren zu können. In verschiedenen Experimenten wurde der Einfluss dieser Polystyrolnanopartikel als Träger auf die Katalysatoreigenschaften wie Aktivität oder Produktivität und die Eigenschaften des produzierten Polyolefins wie z.B. Molekulargewicht und Morphologie untersucht. Im Vergleich zu den PS- Nanopartikeln wurden außerdem PS-Mikropartikel, Silica und Dendrimere als Träger in der heterogenen Olefinpolymerisation eingesetzt. Von all diesen Trägersystemen wurde das Fragmentierungsverhalten durch konfocale Fluoreszenzmikroskopie untersucht. Aus den erhaltenen Ergebnissen kann geschlossen werden, dass die hergestellten Polystyrolnanopartikel neuartige und leistungsfähige Träger für heterogene Polymerisationsprozesse darstellen. Die hergestellten Polystyrolnanopartikel besaßen eine wohldefinierte sphärische Struktur, die eine homogene Verteilung des immobilisierten Metallocenkatalysators und somit auch eine vollständige Fragmentierung des geträgerten Katalysators im hergestellten Polyolefin ermöglichte. Die Katalysatorsysteme, die aus den PS- Nanopartikeln und dem Metallocenkatalysator zusammengesetzt waren, wurden in verschiedenen Polymerisationen wie der Ethylen- oder Propylenhomopolymersation und der Copolymerisation von Ethen mit α- Olefinen getestet. Die Oberflächen- funktionalisierten PS Nanopartikel immobilisierten den Metallocenkatalysator ausreichend gut, so dass kein „Leachen“ (Ablösen) des Katalysators von der Trägeroberfläche festgestellt werden konnte und deshalb Polymer von sehr guter Morphologie erhalten wurde. Um die Fragmentierung des Katalysators und den inneren Aufbau des Polymers näher untersuchen zu können, wurde die konfocale Fluoreszenzmikroskopie für das PS- Nanopartikelträgersystem angewendet. Durch farbstoffmarkierte Trägerpartikel konnte die Verteilung des fragmentierten Katalysators innerhalb des Polymers sichtbar gemacht und analysiert werden. Dabei wurde festgestellt, dass sich PS- Nanopartikel und auch Dendrimere als Träger ähnlich verhalten wie Ziegler- Natta- Katalysatoren, die auf MgCl2 immobilisiert für die heterogene Olefinpolymerisation verwendet werden. Das Fragmentierungsverhalten der Silica oder PS- Mirkopartikel geträgerten Systeme entsprach dagegen dem schichtweisen Fragmentierungsverhalten wie es bereits von Fink und Mitarbeitern beschrieben wurde.

Photo- and redox-active supramolecular systems containing metal complexes

The aim of this Ph.D. project has been the photophysical and photochemical characterization of new photo- and redox-active supramolecular systems. In particular we studied two different classes of compounds: metal complexes and dendrimers. Two different families of bis-cyclometalated neutral Ir(III) complexes are presented and their photophysical properties are discussed. The first family of complexes contains two 2-phenylpyridyl (ppy) or 2-(4,6-difluorophenyl)pyridyl (F2ppy) cyclometalated ligands and an ancillary ligand constituted by a phenol-oxazoline (phox), which can be substituted in the third position with a fluorine group (Fphox). In the second part of this study, we present another family of bis-cyclometalated Ir(III) complexes in which the ancillary ligand could be a chiral or an achiral bis-oxazoline (box). We report on their structural, electrochemical, photophysical, and photochemical properties. Complexes containing phox and Fphox ancillary ligands show blue luminescence with very high quantum yield, while complexes with box ligands do not show particularly interesting photophysical properties. Surprisingly these complexes give an unexpected photoreaction when irradiated with UV light in presence of dioxygen. This photoreaction originates a stable, strong blue emitting and particularly interesting photoproduct. Three successive generations of a family of polyethyleneglycol (PEG)-coated Pd(II) tetrabenzoporphyrin (PdTBP)-based dendritic nanoprobes are presented, and their ability to sensitize singlet oxygen and inflict cellular photodamage are discussed. It was found that the size of the dendrimer has practically no effect on the singlet oxygen sensitization efficiency, that approximate the unity, in spite of the strong attenuation of the triplet quenching rate with an increase in the dendrimer generation. Nevertheless, when compared against a commonly used singlet oxygen sensitizer, as Photofrin, the phosphorescent probes were found to be non-phototoxic. The lack of phototoxicity is presumably due to the inability of PEGylated probes to associate with cell surfaces and/or penetrate cellular membranes. The results suggest that protected phosphorescent probes can be safely used for oxygen measurements in biological systems in vivo. A new family of two photoswitchable (G0(Azo) and G1(Azo)) dendrimers with an azobenzene core, two cyclam units as coordination sites for metal ions, and luminescent naphthalene units at the periphery have been characterized and their coordination abilities have been studied. Because of their proximity, the various functional groups of the dendrimer may interact, so that the properties of the dendrimers are different from those exhibited by the separated functional units. Both the naphthalene fluorescence and the azobenzene photoisomerization can be observed in the dendrimer, but it has been shown that (i) the fluorescent excited state of the naphthalene units is substantially quenched by excimer and exciplex formation and by energy transfer to the azobenzene units, and (ii) in the latter case the fluorescence quenching is accompanied by the photosensitized isomerization of the trans → cis, and, with higher efficiency, the cis → trans reaction. Complexation of these dendrimers, both trans and cis isomers, with Zn(II) ions shows that complexes of 1:1 and 2:1 metal per dendrimer stoichiometry are formed showing different photophysical and photochemical properties compared to the corresponding free ligands. Practically unitary efficiency of the sensitized isomerization of trans → cis and cis → trans reaction is observed, as well as a slight increase in the naphthalene monomer emission. These results are consistent with the coordination of the cyclam amine units with Zn(II), which prevents exciplex formation. No indication of a concomitant coordination of both cyclam to a single metal ion has been obtained both for trans and cis isomer.

Sistemi adesivi con applicazioni in campo biomedicale

Polymeric adhesives have been used for many applications like suture and embolization, instead of classic surgical methods or as for dental uses. In this work both subjects have been investigated and the results separated in two parts. In the first, new dentinal adhesives with different polymerizable groups (methacrylic or vinyl-ethereal) were synthesized. A low sensitivity to hydrolysis and equal or enhanced properties, compared to existing commercial products, were considered essentials. Moreover, these monomers need to polymerize by radical photopolymerization and functional groups of different characteristics were tested. All these products were characterized by microtensile bond strength test to determine the bonding strength between the adhesive and tooth. Concerning embolization, cyanoacrylates are nowadays the most-used adhesives in surgery. Thus, they must respond to several requirements. For instance, polymerization time and adhesive strength need to be low, to avoid diffusion of the products in the body and adhesion to the catheter. In order to overcome these problems we developed new cyanoacrylates, which practically instantly polymerize upon contact with blood but do not demonstrate strong adhesion to the catheter, thank to the presence of fluorine atoms, linked to the ester chain. The synthesis of these products was carried out in several steps, such as the depolymerization of the corresponding oligomers at high temperature in acid conditions. Two types of adhesion strengths were determined. Bonding strength between human veins and a microcatheter was determined in vitro by using organic materials as the most realistic model. Another test, on two layers of skin, was conducted to verify the possible use of these new cyanoacrylates as a glue for sutures. As a conclusion, we were able to demonstrate that some of the prepared monomers posses adhesive strength and polymerization time lower than the commercial product Glubran2.