Responsive hydrogels applied in the biomedical area show great potential as synthetic extracellular matrix mimics and as host medium for cell growth. The hydrogels often lack the characteristic mechanical properties that are typically... more
Responsive hydrogels applied in the biomedical area show great potential as synthetic extracellular matrix mimics and as host medium for cell growth. The hydrogels often lack the characteristic mechanical properties that are typically seen for natural gels. Here, we demonstrate the unique responsive and mechanical properties of hydrogels based on oligo(ethylene glycol) functionalized polyisocyanopeptides. These stiff helical polymers form gels upon warming at concentrations as low as 0.006 %-wt polymer, with materials properties almost identical to those of their intermediate filaments, a class of cytoskeletal proteins. Using a combination of macroscopic rheology and molecular force microscopy the hierarchical relationship between the macroscopic behaviour of theses peptide mimics has been correlated with the molecular parameters.
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Item does not contain fulltext13 november 200
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... perylenebis(dicarboximides): an AFM study†. Vincenzo Palermo *a, Erik Schwartz b, Andrea Liscio a, Matthijs BJ Otten b, Klaus Müllen *c, Roeland JM Nolte b, Alan E. Rowan *b and Paolo Samorì *ad. a Instituto per la Sintesi ...
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ABSTRACT Stable helical polymers with a preferred handedness are compounds that offer intriguing characteristics. This review describes the progress in the synthesis of helical polyisocyanides and the investigations to determine their... more
ABSTRACT Stable helical polymers with a preferred handedness are compounds that offer intriguing characteristics. This review describes the progress in the synthesis of helical polyisocyanides and the investigations to determine their structural properties, such as helical pitch and handedness, by spectroscopic measurements and high resolution AFM. This review is not intended to be comprehensive; its purpose is to highlight recent studies that allow a better understanding of the main aspects of helical polyisocyanides.
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Carbazole functionalized polyisocyanides are known to exhibit excellent electronic properties (E. Schwartz, et al., Chemistry of Materials, 2010, 22, 2597). The functionalities and properties of such materials crucially depend on the... more
Carbazole functionalized polyisocyanides are known to exhibit excellent electronic properties (E. Schwartz, et al., Chemistry of Materials, 2010, 22, 2597). The functionalities and properties of such materials crucially depend on the organization and stability of the polymer structure. We combine solid-state Nuclear Magnetic Resonance (NMR) experiments with first-principles calculations of isotropic chemical shifts, within the recently developed converse approach, to rationalize the origin of isotropic chemical shifts in the crystalline monomer l-isocyanoalanine 2-(9H-carbazol-9-yl) ethyl amide (monomer 1) and thereby gain insight into the structural organization of its polymer (polymer 2). The use of state-of-the-art solid-state NMR experiments combined with Density Functional Theory (DFT) based calculations allows an unambiguous assignment of all proton and carbon resonances of the monomer. We were able to identify the structure stabilising interactions in the crystal and understand the influence of the molecular packing in the crystal structure on the chemical shift data observed in the NMR spectra. Here the Nuclear Independent Chemical Shift (NICS) approach allows discriminating between 'physical' interactions amongst neighboring molecules such as ring-current effects and 'chemical' interactions such as hydrogen bonding. This analysis reveals that the isocyanide monomer is stabilized by multiple hydrogen bonds such as a bifurcated hydrogen bond involving -N-H, -C-H and O=C- moieties and Ar-H···C≡N- hydrogen bonding (Ar = aromatic group). Based on the geometrical arrangement it is postulated that the carbazole units are involved in the weak σ-π interactions giving rise to a Herringbone packing of the molecules. The chemical shift analysis of the polymer spectra readily establishes the existence of N-H···O=C hydrogen bonds despite the limited resolution exhibited by the polymer spectra. It is also elucidated that the relative arrangement of the carbazole units in the polymer differs significantly from that of the monomer.
Research Interests: Chemistry, Physical Organic Chemistry, Carbon, Nuclear Magnetic Resonance, Medicine, and 15 moreCrystals, Organization, Density Functional Theory, Organisation, Physical sciences, Chemical Analysis, Hydrogen Bond, CHEMICAL SCIENCES, Monomer, Chemical Shift, Carbazole, Calculation, Molecule, Electronic Structure of Materials, and Physical chemistry and chemical physics
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Photovoltaic devices incorporating perylene-substituted polyisocyanide materials have been demonstrated, using blend systems with polythiophene-and polyfluorene-based conjugated polymers. Prototypical structures with nominal (1:1) blend... more
Photovoltaic devices incorporating perylene-substituted polyisocyanide materials have been demonstrated, using blend systems with polythiophene-and polyfluorene-based conjugated polymers. Prototypical structures with nominal (1:1) blend weight ratios of the ...
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ABSTRACT The success of polyisocyanides as the basic scaffold for functional materials has been attributed to its rigid and highly stable structure. It has been demonstrated that these polymers can be stabilized by formation of inter side... more
ABSTRACT The success of polyisocyanides as the basic scaffold for functional materials has been attributed to its rigid and highly stable structure. It has been demonstrated that these polymers can be stabilized by formation of inter side chain hydrogen bonds (CornelissenScience 2001, 293, 676) which in turn has resulted in development of several polyisocyanide based functional materials. Despite the success of the material, the exact structure and conformation of these polymers has been subject of discussions over many years and several structural models based on evidence from different analytical and theoretical methods have been proposed. This study determines the structure of the isocyanide dipeptide polymer using solid-state NMR spectroscopy. Two-dimensional separated-local-field and double-quantum single-quantum spectroscopic methods have been employed to obtain structural constraints for the polymer backbone. These constraints were used to build a molecular model and subsequently subjected to molecular dynamics simulations. The backbone structure of the polyisocyanide is determined to be a 154 helix with hydrogen bonding interactions between n and n + 4 side chains.
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We show that the screw sense of polyisocyanide helices can be determined in a simple manner from the vibrational circular dichroism (VCD) of their CN-stretching mode. The relation between VCD and molecular structure is obtained using the... more
We show that the screw sense of polyisocyanide helices can be determined in a simple manner from the vibrational circular dichroism (VCD) of their CN-stretching mode. The relation between VCD and molecular structure is obtained using the coupled-oscillator approximation. It is shown that since the C═N groups point approximately radially outward from the helical axis, the CN-stretch region of the VCD spectrum of a polyisocyanide helix consists of a single couplet, the sign of which is directly related to the screw sense of the helix. We use this method to determine the screw sense of poly(R)-2-isocyanooctane and poly(S)-2-isocyanooctane from their VCD spectrum.
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... thumbnail image. From eq 1 we obtain a L w of 134 nm and a L n of 103 nm. Assuming a 4 1 type helix with a helical pitch of 0.46 nm (as measured by Powder X-ray diffraction of LL-PIAA)2 these values16 amount to a M w of 293 kg/mol and... more
... thumbnail image. From eq 1 we obtain a L w of 134 nm and a L n of 103 nm. Assuming a 4 1 type helix with a helical pitch of 0.46 nm (as measured by Powder X-ray diffraction of LL-PIAA)2 these values16 amount to a M w of 293 kg/mol and a M n of 226 kg/mol. ...
Research Interests: Materials Engineering, Chemistry, Polymer Chemistry, Physical Organic Chemistry, Solid State Chemistry, and 11 moreClick chemistry, Polymer, Secondary Structure, Acetylene, Water soluble polymers, Saponification, Aqueous Solution, Hydrolysis, Copolymerization, Methyl Ester, and Chemical Modification
Research Interests: Engineering, Bioengineering, Condensed Matter Physics, Materials Science, Chemistry, and 15 moreBiomedical Engineering, Medicine, Polymer, Light, Nanostructures, CHEMICAL SCIENCES, Particle Size, Carbazole, Photovoltaic system, Electrodes, Cyanides, Equipment Design, Equipment Failure Analysis, Polycarbazole, and Acceptor
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Research Interests: Engineering, Chemistry, Materials Chemistry, Polymer Chemistry, Physical Organic Chemistry, and 14 moreSpectroscopy, Materials, Atomic Force Microscopy, Click chemistry, Polymer, Material Chemistry, Copper, Macromolecules, Solubility, CHEMICAL SCIENCES, Macromolecule, Acetylene, Molecular weight, and Chemical Synthesis
Research Interests: Engineering, Chemistry, Physical Organic Chemistry, Spectroscopy, Nonlinear dynamics, and 15 morePolymers, Chemical Physics, Medicine, Computer Simulation, Infrared spectroscopy, Fundamental Frequency, Physical sciences, Electronic Structure, Hydrogen Bond, CHEMICAL SCIENCES, Infrared, Femtosecond, Infrared spectra, Trapping, and Molecular Conformation
Research Interests: Chemistry, Crystallography, Catalysis, X ray absorption spectroscopy, Medicine, and 14 morePolymerization, Crystal structure, X Rays, Absorption spectroscopy, Emulsion polymerisation, Nickel, XANES, X ray diffraction, Single Crystal, THEORETICAL AND COMPUTATIONAL CHEMISTRY, Reaction Mechanism, extended x-ray absorption fine structure (EXAFS), Crystalline Structure, and isocyanide
Research Interests: Chemistry, Crystallography, Physical Organic Chemistry, Quantum Theory, Vibration, and 12 moreMedicine, Circular Dichroism, Nitriles, Peptides, CHEMICAL SCIENCES, Protein Secondary Structure Prediction, Spectrum analysis, Twist, Vibrational circular dichroism, Molecular Conformation, Protein Conformation, and dihedral angle
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Research Interests: Chemistry, Electrochemistry, Polymers, Chemical Physics, Medicine, and 15 moreElectron, Peptides, Electron Transport, Hydrogen Bond, CHEMICAL SCIENCES, Polyurethanes, Exciton, Charge Density, Perylene, Molecule, Molecular Dynamic Simulation, Right Handed, Molecular Structure, Polyisocyanides, and Molecular dynamic
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Femtosecond vibrational pump-probe spectroscopy on beta-helical polyisocyanopeptides reveals vibrational self-trapping in the well-defined hydrogen-bonded side groups that is absent when non-hydrogen bonded monomers are mixed in.