We report a macromolecular end‐capping approach to improve the detection sensitivity of cationic conjugated polymer (CCP) based DNA detection. A phenylethynyl anthracene (PEA) end‐capped cationic polyfluorene (PF) derivative ( P1 ) is synthesized via Suzuki coupling. Due to efficient fluorescence resonance energy transfer (FRET) from the polymer backbone to the end‐capper PEA units, the polymer ( P1 ) fluorescence is dominated by the emission from PEA even in dilute aqueous solution. P1 emission has a better spectral overlap with fluorescein (Fl) absorption compared to that for uncapped PF ( P2 ). In addition, the intra and intermolecular energy transfer for P1 is more efficient in the presence of DNA due to complexation‐induced polymer aggregation. These impart a combinatorial FRET between P1 and an Fl‐labeled probe which is more efficient than that between P2 and the same probe. P1 thus offers a better DNA detection sensitivity relative to P2 and opens up new opportunities to improve the performance of CCP based biosensors involving FRET.
The mechanical behaviour of monodomain nematic side‐chain liquid‐crystalline elastomers containing azoderivatives as pendant groups or crosslinkers has been studied under UV irradiation and in the darkness at different temperatures. From the evaluation of the opto‐mechanical experiments, the mechanical efficiency, kinetic rates, activation energies and the isomerization mechanism of the azocompounds in the liquid‐crystalline matrix could be determined, as well as the effect of the chemical constitution of the azobenzene derivatives and their role in the elastomeric network.
A new donor–acceptor polymer based on 9,9‐dioctylfluorene is synthesized and tested in organic photovoltaic devices. Results show that the polymer exhibits good solubility in a range of organic solvents and has a high hole mobility. When blended with a PC70BM acceptor and fabricated into a bulk heterojunction, photovoltaic devices having a maximum power conversion efficiency (PCE) of 6.2% and a peak external quantum efficiency of 74% are created. Such efficiencies are realized without any necessity for solvent additives or thermal annealing protocols.
A polymer–surfactant micellar complex has been studied as a fluorescence resonance energy transfer (FRET) donor to fluorescein‐labeled DNA (ssDNA‐Fl). In water, the molar absorptivity and fluorescence quantum efficiency of cationic poly(fluorene‐co‐phenylene) (c‐PFP) are substantially increased in the presence of non‐ionic surfactants. A TEM microscopic study shows the formation of a nanowire micellar complex of c‐PFP and the surfactants. About a 400% enhancement of the FRET signal is measured in c‐PFP/ssDNA‐Fl with Brij 30, relative to that without surfactants. The signal amplification is successfully modulated using different types of non‐ionic surfactants which perturb the complexation, fine‐structure of the complex (i.e., donor‐acceptor separation), and the resulting energy transfer process.
This paper focuses on the attachment of densely grafted polymer layers (polymer brushes) to various inorganic and polymeric substrates by the “grafting to” method. A brief overview of synthesis of polymer brushes by the method is first provided, with emphasis on chemical approaches to polymer attachment. The second part of the paper covers the synthesis of polymer layers via a recently developed macromolecular anchoring layer approach. Several examples of application of the grafting technique are presented for generation of hydrophobic, hydrophilic, gradient, and switchable surfaces.
Using two‐photon absorption, an array of spots in a dye‐doped polymer film can be bleached, creating a three‐dimensional structure that can be imaged with two‐photon or confocal microscopy. Microscopic deformations resulting from various treatments to the film can be characterized, for example, swelling or shrinking. This technique is demonstrated on dye‐doped poly(vinyl alcohol), in which the effect of swelling with the addition of water to the film is shown.
Summary: The vapor‐based synthesis and characterization of a reactive polymer, poly[(4‐formyl‐p‐xylylene)‐co‐(p‐xylylene)] ( 1 ), have been reported. The reactive polymer coating enables the immobilization of oligosaccharides via the chemoselective aldehyde‐hydrazide coupling reaction.
Summary: Amphiphilic hyperbranched polyester (H20‐AM) with methacrylate end groups was synthesized based on hyperbranched aliphatic polyester (Boltorn™ H20). Narrow‐dispersed crosslinkable vesicles were obtained by dissolving H20‐AM in water, and characterized by laser light scattering and TEM. The hollow structural vesicle is composed of around 350 H20‐AM molecules, having a radius of around 40 nm and of 1.9 × 106 g · mL−1. The vesicles were fixed by crosslinking of methacrylate groups to form shape‐persistent structures.
TEM images of the crosslinked vesicles at lower magnification. 相似文献
A simple and direct method for derivatization of solid polysaccharides is presented. The novel methodology is based on the combination of organic acid‐catalyzed esterification or etherification and photochemical thiol‐ene click derivatization of a heterogeneous polysaccharide. The solid cellulose was “organoclick” modified with aryl, alkyl and polyester groups, respectively. The modification allows for a highly modular and metal free surface modification of solid polysaccharides.
The computer‐aided design of polymers is one of the holy grails of modern chemical informatics and of significant interest for a number of communities in polymer science. This paper outlines a vision for the in silico design of polymers and presents an information model based on modern semantic web technologies, thus laying the foundations for achieving the vision.
A method to prepare shape‐changing nanospheres from liquid crystalline elastomers is reported. The nanosized colloids are prepared by a miniemulsion process. During this process, colloids are prepared from a liquid crystalline (LC) main‐chain polyester and subsequently crosslinked into a nanometer‐sized LC elastomer. The ability of these LC elastomers to change their shape at the phase transition temperature from the smectic A to the isotropic phase was detected by temperature‐dependent transmission electron microscopy. The phase transition‐induced shape change leads to strongly shape anisotropic nanosized elastomer particles.
Summary: The cyclopolymerization of 4,4‐bis(hydroxymethyl)‐1,6‐heptadiyne ( M1 ), 4‐(carboxyethyl)‐1,6‐heptadiyne ( M2 ), 4‐(hydroxymethyl)‐1,6‐heptadiyne ( M3 ), and 4‐carboxy‐1,6‐heptadiyne ( M4 ) using five different well‐defined metathesis initiators was investigated. Control of molar mass was achieved with catalysts bearing trifluoroacetate ligands. 13C NMR experiments showed that poly‐ M2 , prepared by the action of any catalyst consisted solely of five‐membered ring structures, i.e., 1,2‐(cyclopent‐1‐enylene)vinylene units. Effective conjugation lengths of all polymers were calculated from the corresponding UV‐Vis absorption maxima, which varied reversibly with temperature.
