A cationic poly(p-phenylene vinylene) related copolymer without bulky phenylene substitutents attached to the conjugated backbone was prepared through Wittig reaction.The molecular structure and optical properties were highly investigated through ~1H-NMR,UV and PL spectroscopy.The quenching behavior was also investigated,and the results demonstrate that incomplete quenching exists,which is consistent with the cationic poly(p-phenylene vinylene) related copolymer containing bulky phenylene substitutents,p... 相似文献
The electrochemical synthesis of poly(p-phenylenevinylene) (PPV) and different modifications in the electronic distribution upon electrochemical p-doping (oxidation)
and n-doping (reduction) of this polymer film have been studied in situ by resonance Raman spectroscopy, optical absorption
spectroscopy and ESR spectroscopy. The polymer film has been prepared by electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene in dimethylformamide using tetraethylammonium tetrafluoroborate as the electrolyte salt. During electrochemical polymerization
the position and relative intensities of the Raman bands change regularly as the chain length increases and finally converge
on values reported for chemically prepared PPV. The Raman spectra for electrochemically polymerized PPV is compared to infrared-active
vibration bands for electrochemically n-doped PPV. When the polymer undergoes redox reactions (doping-dedoping), shifts and
broadening of Raman bands, compared to neutral PPV, are observed. Interpretation of the Raman spectra and the ESR results
led to the conclusion that charge transfer in this system is mainly accomplished by polaron species formed upon doping of
the polymer. In this reaction the quinoid structure is formed rather than the benzenoid structure.
Electronic Publication 相似文献
Results of density-functional studies of the electronic properties of poly(p-phenylene-vinylene) (PPV) and polybutadiene are presented. The calculations were performed using a single-chain, full-potential, linearized muffin-tin orbital (LMTO)-based method. In particular, we analyze the effects on the electronic properties due to the addition of substituents to the vinylene linkage. As substituents, we concentrate on cyano and amine groups. It is found that these groups induce large changes in the band structures of these systems, particularly of the bands closest to the Fermi level. Further, the effects on the band gap and on the total energy due to the bond-length alternation of the polymer backbones, are analyzed both for unsubstituted and substituted polybutadiene. It is found that both properties depend sensitively on both the substituents attached to the chain and on the precise structure of the polymer. The substituents lead to overall redistributions of the electrons and, in particular, the disubstituted PPV is found to have a large dipole moment perpendicular to the polymer axis. For disubstituted polybutadiene we find a stronger C–C bond-length alternation than for the unsubstituted compound (polyacetylene), and the results for this compound indicate that the band gap of substituted and unsubstituted PPV depends strongly on the bond-length alternation. 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
Hybrid materials composed of phase‐separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block‐copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one‐dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light‐emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains. 相似文献
A novel amine‐functionalized polycarbonate was synthesized and its excellent gene transfection ability in vitro is demonstrated. In the framework of adapting the cationic polycarbonate for in vivo gene delivery applications, here the design and synthesis of biodegradable block copolymers of poly(ethylene glycol) (PEG) and amine‐functionalized polycarbonate with a well‐defined molecular architecture and molecular weight is achieved by metal‐free organocatalytic ring‐opening polymerization. Copolymers in triblock cationic polycarbonate‐block‐PEG‐block‐cationic polycarbonate and diblock PEG‐block‐cationic polycarbonate configurations, in comparison with a non‐PEGylated cationic polycarbonate control, are investigated for their influence on key aspects of gene delivery. Among the polymers with similar molecular weights and N content, the triblock copolymer exhibit more favorable physicochemical (i.e., DNA binding, size, zeta‐potential, and in vitro stability) and biological (i.e., cellular uptake and luciferase reporter gene expression) properties. Importantly, the various cationic polycarbonate/DNA complexes are biocompatible, inducing minimal cytotoxicities and hemolysis. These results suggest that the triblock copolymer is a more useful architecture in future cationic polymer designs for successful systemic therapeutic applications. 相似文献