Well defined oligo(phenylene vinylene) grafted polymers known as oligo(phenylene vinylene)-poly(methylstyrene) hybrids have been developed using a step-wise synthetic protocol, where the length of the OPV can be controlled systematically to achieve specific optoelectronic properties. The process allows the structural modification of attached OPV at a molecular level either by varying the chain length or by changing functionalities. The step-wise generation of OPV chains on the backbone of a highly soluble polymer ensures solubilization in a variety of solvents and also the exhibition of interesting optical properties. 相似文献
A dendrimer having phenylene vinylene and phenylene ethynylene moieties, a twisted core, and eighteen chiral centers on the periphery has been prepared in high yield by using Sonogashira and Horner–Wadsworth–Emmons reactions. UV–visible and fluorescence spectra and circular dichroism measurements have been envisaged to study the aggregation behavior. 相似文献
In this paper, in situ atomic force microscopy has been used to investigate the micellization and self-assembling structure of an amphiphilic rod-coil block oligomer (EO16OPV) containing a conjugated oligo(phenylene vinylene) dimer and poly(ethylene oxide) at the mica-water interface. It is found that EO16OPV molecules have strong adsorption and aggregation properties on mica. In the wide concentration range from above the critical micelle concentration (cmc) to far below the cmc, a closely packed layer of stripe-like micelles with two preferred orientations can be formed at the mica-water interface. A cylindrical micelle structure for the stripes is proposed. We demonstrate that the stripe-like micelles formed on mica originate from different micellization processes at solution concentrations above and below the cmc. The origins of the strong micellization properties and oriented arrangement of the stripes are also discussed. 相似文献
Over the past 2 years, various symmetrical and unsymmetrical bipolar amphiphiles (bolaamphiphiles) have been synthesized to study their self-organizing and packing properties alone as well as in mixtures with conventional amphiphiles. This review focuses on the lyotropic properties of these bolaamphiphiles and describes their in some cases quite unusual supramolecular self-assembling properties in aqueous media and at the air–water and liquid–solid interface. 相似文献
Three organic sensitizers containing bis-dimethylfluorenyl amino donor and a cyanoacrylic acid acceptor bridged by p-phenylene vinylene unit were synthesized. The power conversion efficiency was quite sensitive to the length of bridged phenylene vinylene groups. A nanocrystalline TiO2 dye-sensitized solar cell was fabricated using three sensitizers. The maximum power conversion efficiency of JK-59 reached 7.02%. 相似文献
The synthesis and aqueous self‐assembly of a new class of amphiphilic aliphatic polyesters are presented. These AB block polyesters comprise polycaprolactone (hydrophobe) and an alternating polyester from succinic acid and an ether‐substituted epoxide (hydrophile). They self‐assemble into biodegradable polymersomes capable of entering cells. Their degradation products are bioactive, giving rise to differentiated cellular responses inducing stromal cell proliferation and macrophage apoptosis. Both effects emerge only when the copolymers enter cells as polymersomes and their magnitudes are size dependent. 相似文献
The synthesis and aqueous self‐assembly of a new class of amphiphilic aliphatic polyesters are presented. These AB block polyesters comprise polycaprolactone (hydrophobe) and an alternating polyester from succinic acid and an ether‐substituted epoxide (hydrophile). They self‐assemble into biodegradable polymersomes capable of entering cells. Their degradation products are bioactive, giving rise to differentiated cellular responses inducing stromal cell proliferation and macrophage apoptosis. Both effects emerge only when the copolymers enter cells as polymersomes and their magnitudes are size dependent. 相似文献
The highly conjugated aromatic polymers, poly(2,5-dimethoxyphenylene vinylene) and poly(2,5-dimethylphenylene vinylene), were obtained from their water soluble, sulfonium salt precursor polymers. Films of these polymers were reacted with either AsF5 or I2 vapor. Poly(2,5-dimethoxyphenylene vinylene) showed increases in electrical conductivity of up to 14 to 15 orders of magnitude for these two dopants, while an 8 to 9 order of magnitude increase was observed for poly(2,5-dimethylphenylene vinylene) with the same dopants. The synthesis of the precursor polymers, the properties and elimination reactions of films of the precursors, the doping reactions, and the conductivities of the resulting phenylene vinylene films are discussed. 相似文献
Summary: A novel poly(p‐phenylene vinylene) (PPV)/poly(p‐phenylene ethynylene) (PPE) block‐copolymer was synthesized by a cross‐coupling polycondensation with Pd(PPh3)2Cl2 and a phase‐transfer catalyst, and was confirmed by 1H NMR and IR spectroscopy and elemental analysis. The thermal, electrochemical, and photoluminescent properties of the new copolymer have been investigated. The incorporation of triple bonds into the cyano‐substituted PPV (CN‐PPV) backbone leads to higher oxidation and reduction potentials than poly(2‐methoxy‐5‐(2‐ethylhexyloxy)‐p‐phenylene vinylene) (MEH‐PPV) and CN‐PPV, potentially making the copolymer a good electron‐transporting material for use in a light‐emitting‐diode device.
The cyclic voltammogram of the novel poly(p‐phenylene vinylene) (PPV)/poly(p‐phenylene ethynylene) (PPE) block‐copolymer synthesized here. 相似文献
We construct a phase diagram for self-assembling biologically active peptide amphiphiles. The structure and stability of the assemblies are studied as a function of pH and salinity of the solution. The general features of the phase diagram are predicted based on theoretical modeling of the self-assembly process, as well as experimental data, and further experiments are performed to verify and ascertain the boundary locations of the diagram. Depending on solution conditions, the amphiphiles can form cylindrical or spherical micelles, intermediate structures between these, or may not assemble at all. We also demonstrate that changing conditions may result in phase transitions among these structures. This type of phase diagram could be useful in the design of certain supramolecular nanostructures by providing information on the necessary conditions to form them. 相似文献
A single‐strand arylene–vinylene precursor containing four phenylene and three naphthylene units linked together with six vinylene spacers undergoes helical folding via sextuple photocyclization to give a [16]helicene core in a single step. The phenylene and naphthylene units are arranged in the precursor such that unfavorable side reactions (anthracene or benzoperylene formation) are avoided, and this is the key to the success of the one‐step synthesis of [16]helicene, which is the longest [n]helicene that has been synthesized to date. 相似文献
Biomaterials made from self-assembling, short peptides and peptide derivatives have great potential to generate powerful new therapies in regenerative medicine. The high signaling capacity and therapeutic efficacy of peptidic scaffolds has been established in several animal models, and the development of more complex, hierarchical structures based on peptide materials is underway. This highlight discusses several classes of self-assembling peptide-based materials, including peptide amphiphiles, Fmoc-peptides, self-complementary ionic peptides, hairpin peptides, and others. The self-assembly designs, bioactive signalling strategies, and cell signalling capabilities of these bioactive materials are reported. The future challenges of the field are also discussed, including short-term goals such as integration with biopolymers and traditional implants, and long term goals, such as immune system programming, subcellular targeting, and the development of highly integrated scaffold systems. 相似文献
As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly (phenylene vinylene) (PPV), poly(2,5-thienylene vinylene) (PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics (NAMD) based on time-dependent density-functional theory (TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations. 相似文献
Silicone surfactants are widely used in many industries and mostly rely on poly(ethylene glycol) (PEG) as the hydrophile. This can be disadvantageous because commercial PEG examples vary significantly in polydispersity—constraining control over surface activity of the surfactant—and there are environmental concerns associated with PEG. Herein, we report a three-step synthetic method for the preparation of saccharide-silicone surfactants using the natural linker, cysteamine, and saccharide lactones. The Piers–Rubinsztajn plus thiol-ene plus amidation process is attractive for several reasons: if employed in the correct synthetic order, it allows for precise tailoring of both hydrophobe and hydrophile; it permits the ready utilization of natural hydrophiles cysteamine and saccharides in combination with silicones, which have significantly better environmental profiles than PEG; and the products exhibit interesting surface activities. 相似文献