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ABSTRACT: We live in a world full of synthetic materials, and the development of new technologies builds on the design and synthesis of new chemical structures, such as polymers. Synthetic macromolecules have changed the world and currently play a major role in all aspects of daily life. Due to their tailorable properties, these materials have fueled the invention of new techniques and goods, from the yogurt cup to the car seat belts. To fulfill the requirements of modern life, polymers and their composites have become increasingly complex. One strategy for altering polymer properties is to combine different polymer segments within one polymer, known as block copolymers. The microphase separation of the individual polymer components and the resulting formation of well defined nanosized domains provide a broad range of new materials with various properties. Block copolymers facilitated the development of innovative concepts in the fields of drug delivery, nanomedicine, organic electronics, and nanoscience. Block copolymers consist exclusively of organic polymers, but researchers are increasingly interested in materials that combine synthetic materials and biomacromolecules. Although many researchers have explored the combination of proteins with organic polymers, far fewer investigations have explored nucleic acid/polymer hybrids, known as DNA block copolymers (DBCs). DNA as a polymer block provides several advantages over other biopolymers. The availability of automated synthesis offers DNA segments with nucleotide precision, which facilitates the fabrication of hybrid materials with monodisperse biopolymer blocks. The directed functionalization of modified single-stranded DNA by Watson-Crick base-pairing is another key feature of DNA block copolymers. Furthermore, the appropriate selection of DNA sequence and organic polymer gives control over the material properties and their self-assembly into supramolecular structures. The introduction of a hydrophobic polymer into DBCs in aqueous solution leads to amphiphilic micellar structures with a hydrophobic polymer core and a DNA corona. In this Account, we discuss selected examples of recent developments in the synthesis, structure manipulation and applications of DBCs. We present achievements in synthesis of DBCs and their amplification based on molecular biology techniques. We also focus on concepts involving supramolecular assemblies and the change of morphological properties by mild stimuli. Finally, we discuss future applications of DBCs. DBC micelles have served as drug-delivery vehicles, as scaffolds for chemical reactions, and as templates for the self-assembly of virus capsids. In nanoelectronics, DNA polymer hybrids can facilitate size selection and directed deposition of single-walled carbon nanotubes in field effect transistor (FET) devices.
Accounts of Chemical Research 06/2012; 45(9):1419-30. · 21.64 Impact Factor
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ABSTRACT: We report a comparative study on the self-assembly from solution and electrical characterization of n-type semiconducting fibres obtained from five different perylenebis(dicarboximide) (PDI) derivatives. In particular we investigated the role of the nature of the alkyl chain covalently linked to the N,N' sites of the PDI in modulating the molecular solubility and aggregation capacity. We explored the morphologies of the self-assembled architectures physisorbed on dielectric surfaces and in particular how they can be modified by tuning the deposition and post-deposition procedures, i.e. by modulating the kinetics of the self-assembly process. To this end, alongside the conventional spin-coating, solvent vapour annealing (SVA) and solvent induced precipitation (SIP) have been employed. Both approaches led to fibres having widths of several hundred nanometres and lengths up to tens of micrometres. SVA formed isolated fibres which were tens of nanometres high, flat, and tapered at the ends. Conversely, SIP fibres exhibited nearly matching heights and widths, but organized into bundles. Despite these morphological differences, the same intermolecular packing is found by XRD in each type of structure, albeit with differing degrees of long-range order. The study of the electrical characteristics of the obtained low dimensional nano-assemblies has been accomplished by fabricating and characterizing organic field-effect transistors.
Nanoscale 03/2012; 4(7):2387-93. · 5.91 Impact Factor
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ABSTRACT: Three new photostable rylene dyes for applications in single molecule studies and membrane labelling have been synthesized and their photophysical properties were characterized. These dyes differ in the number of polyethylene glycol (PEG) chains attached to the core structure which is either a perylene derivate or a terrylene derivate. One perylene and one terrylene dye is modified with two PEG chains, and another terrylene derivate has four PEG chains. The results show that the terrylene dye with four PEG chains (4-PEG-TDI) forms soluble nonfluorescing H-aggregates in water, so that the absorption bands are blue-shifted with respect to those of the fluorescing monomeric form. The presence of a surfactant such as Pluronic P123 leads to the disruption of the aggregates due to the formation of monomers in micelles and a strong increase in fluorescence. Application for labelling cell membranes can be considered for this dye since it adsorbs in a similar way as monomer to a lipid bilayer. Furthermore a single-molecule study of all three rylene dyes in polymeric films of PMMA showed excellent photostability with respect to photobleaching, far above the photostability of other common water-soluble dyes, such as Oxazine-1, Atto647N, Cy5, Alexa647 and Rhodamin6G. Especially 4-PEG-TDI seems to be a promising dye for membrane labelling with its high photostability.
ChemPhysChem 12/2010; 12(8):1588-95. · 3.41 Impact Factor
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ABSTRACT: Always on the move: Molecular dynamics of perylene cores in columnar structures influences the processability and self-healing of these materials. A combination of X-ray scattering and advanced solid-state NMR methods show that these systems have restricted angular mobility of the cores even in the frozen phase, and a cooperative spiral type of motion in the liquid crystalline phase (see picture).
Angewandte Chemie International Edition 06/2009; 48(25):4621-4. · 13.45 Impact Factor
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Angewandte Chemie International Edition 02/2008; 47(4):783-7. · 13.45 Impact Factor
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Cristina Flors,
Ingo Oesterling, Tobias Schnitzler,
Eduard Fron,
Gerd Schweitzer,
Michel Sliwa,
Andreas Herrmann,
Mark Van der Auweraer,
Frans C De Schryver,
Klaus Müllen,
Johan Hofkens
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ABSTRACT: Shape persistent perylene diimide (PDI) multichromophores incorporating ethynylene bridges have been synthesized in high yield via palladium-catalyzed Hagihara coupling, which provides compounds with no rotational or constitutional isomerism in contrast to polyphenylene dendrimers. Their excited-state pathways have been studied at the ensemble and at the single-molecule level and compared to several model compounds. In an apolar solvent, energy hopping and/or energy transfer between the chromophoric units are the dominating processes. In a polar medium, energy hopping is still operative, but electron transfer from the phenyl ethynylene bridge to the chromophore occurs if the former is connected to the bay area of PDI. This effect should be considered when further developing this type of multichromophore, as this nonradiative deactivation process might be unwanted for applications such as optical and electronic devices. At the single-molecule level, the fluorescence intensity traces are characterized by rich on-off dynamics, which we attribute to oxygen-enhanced intersystem crossing leading to the formation of a long-lived dark charge-separated state.
03/2007;
