Near‐infrared (NIR) polymer light‐emitting diodes (PLEDs) based on a fluorene–dioctyloxyphenylene wide‐gap host material copolymerized with a low‐gap emitter are presented. Various loadings (1, 2.5, 10, 20 mol%) of the low‐gap emitter are studied, with higher loadings leading to decreased efficiencies likely due to aggregation effects. While the 10 mol% loading resulted in almost pure NIR emission (>99.6%), the 1 mol% loading yielded optimum device performance, which is among the best reported to date for a unblended single‐layer pure polymer emitter, with an external quantum efficiencies of 0.04% emitting at 909 nm. The high spectral purity of the PLEDs combined with their performance support the methodology of copolymerization as an effective strategy for developing NIR PLEDs.
Summary: A class of new, soluble, π‐conjugated polymers containing a fumaronitrile unit in the main chain were synthesized by the reaction between di(4‐bromophenyl)fumaronitrile and bis(2,2‐dimethylpropane‐1,3‐diyl)‐1,4‐dialkoxyphenylene‐2,5‐diborate employing palladium catalysts. All the polymers were photoluminescent and electrochemically active.
The new soluble π‐conjugated polymers 1a – d with photoluminescence and electrochemical activity synthesized here. 相似文献
The monomer 3‐ethyl‐1‐vinyl‐2‐pyrrolidone ( 3 ) and the homopolymer poly(3‐ethyl‐1‐vinyl‐2‐pyrrolidone) ( 5 ) have been synthesized. Polymer 5 is soluble in water and shows a critical temperature (Tc) of 27 °C. The presence of cyclodextrin causes a slight shift of the Tc. The lower critical solution temperature (LCST) could be varied between 27 and 40 °C by copolymerization with N‐vinyl‐2‐pyrrolidone. A linear correlation between the Tc and the copolymer composition is observed.
Ring‐opening metathesis polymerization (ROMP) was used for the synthesis of monolithic capillary columns with inner diameters of 200 µm. The resulting polymeric monoliths were characterized by inverse size‐exclusion chromatography (ISEC). Surface functionalization was carried out in situ using 2‐(N,N‐dimethylaminoethyl)norborn‐5‐ene‐2‐ylcarboxylic amide ( 1 ). The resulting functionalized monoliths were successfully used in anion‐exchange chromatography of oligodeoxynucleotides.
Precise nano‐ and microscale control of the architecture of biodegradable biomaterials is desirable for several biotechnological applications such as drug delivery, diagnostics, and medical imaging. Herein, we combine electrohydrodynamic co‐jetting and highly specific surface modification (via Huisgen 1,3‐dipolar cycloaddition) to prepare particles and fibers with spatioselective surface modification. We first prepared biphasic particles and fibers from commercial poly(lactide‐co‐glycolide) copolymers via electrohydrodynamic co‐jetting of two organic solutions loaded with fluorescent macromolecules and acetylene‐modified PLGA derivatives. (i) Spatially controlled reaction of poly[lactide‐co‐(propargyl glycolide)] with O‐(2‐aminoethyl)‐O′‐(2‐azidoethyl)heptaethylene glycol and (ii) subsequent conversion of the newly introduced amino groups with fluorescence probes resulted in particles and fibers with surface modification of one hemisphere only.
A new sol‐gel hybrid film based on heterocyclic chromophore, namely 2‐[4′‐(N‐ethyl‐N‐hydroxyethyl)amino phenyl azo]‐4,5‐dicyanoimidazole (IZ), has been synthesized and characterized. The hybrid system possesses a high chromophore loading density up to 65 wt.‐% without observing a phase separation. The initial decomposition temperatures of the chromophore and hybrid material were determined to be 260 and 272 °C, respectively. Poled films show a fairly high and stable nonlinear optical (NLO) response, even at an elevated temperature.
New multifunctional copoly(2‐oxazoline) nanoparticles were prepared for cell studies. The polymer contains double‐bond side chains as potential reaction sites for “thio”‐click reactions as well as a fluorescein label covalently bound to the polymer backbone. Using the nanoprecipitation technique, spherical nanoparticles of 200–800 nm were obtained. Confocal laser scanning microscopy measurements revealed the cellular uptake of the nanoparticles.
Summary: A soft‐lithographic imprinting approach to fabricate super‐hydrophobic surfaces has been developed in this work. In this process, fresh lotus leaves were used as masters and PDMS stamps were prepared by replica molding against the lotus‐leaf surfaces. By using the stamps and an epoxy‐based azo polymer solution as “ink”, the mimicked lotus‐leaf surfaces made of the polymer were fabricated by pressing the featured faces of the stamps against “inked” substrates and drying under a proper condition after peeling off the stamps. The lotus‐leaf‐like surfaces show super‐hydrophobic characteristics with the water contact angle higher than 150° and contact angle hysteresis less than 3°.
SEM images of lotus‐leaf‐like papillary structures on the imprinted surface. 相似文献
π‐Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4‐c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave‐assisted Yamamoto or Sonogashira cross‐coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m2 · g−1.
Herein, a convenient and general method to simultaneously fix and functionalize polymeric vesicles with sulphydryl groups by the co‐self‐assembly of poly(ethylene oxide)‐block‐poly[3‐(triethoxysilyl)propyl methacrylate] (PEO‐b‐PTESPMA) and 3‐mercaptopropyltrialkoxysilane in an aqueous solution is reported. The presence of sulphydryl groups across the vesicle membrane has been confirmed by using an energy‐filtered technique during TEM analysis and by capturing Au nanoparticles.
A novel fluorescent nanoparticle with reversible on‐off switching properties has been synthesized. Three different wavelengths of light are used for switching‐on light, switching‐off light and excitation light, respectively. Thus, when this particle is used as a fluorescent probe by irradiation of the excitation light, the on‐off status can be maintained. We also showed that the on‐off status of the fluorescent particle even embedded in hydrogels can be remotely controlled by using two different wavelengths of light. These results promise that this kind of fluorescent particles will introduce a new concept and it will possibly be applied as a novel fluorescent probe, a photo memory, and a switching devise for photonics.
Macroporous temperature‐sensitive poly(N‐isopropylacrylamide) (PNIPA) hydrogels were prepared by a novel phase‐separation technique to improve the response properties. In comparison with a conventional PNIPA hydrogel prepared in water, these macroporous hydrogels, prepared by polymerization in aqueous sucrose solutions, have higher swelling ratios at temperatures below the lower critical solution temperature and exhibit much faster response rates to temperature changes.
Scanning electron microscopy image of the surface of a PNIPA hydrogel, prepared in 1.50 M aqueous sucrose solution. 相似文献
Mussel adhesives function as tools for surface modifications of a wide variety of materials due to their remarkable adhesion properties. Herein, a combination of bioinspired mussel adhesives based on a dopamine derivative, polymer chemistry, and well‐established Diels–Alder (DA) chemistry leads to a bioinspired switchable surface system that possesses the capability of attaching and detaching specific polymers on demand. A dopaminemaleimide compound, which has been attached to a gold surface under maritime conditions undergoes DA‐ and retro‐DA‐click‐conjugations with cyclopentadiene‐carrying PEG chains. The surface attachment and the subsequent DA/rDA cycles are evidenced via XPS analysis.
Well‐defined polymethylene‐block‐polystyrene (PM‐b‐PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl‐terminated polymethylenes (PM‐OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM‐MIs ( = 1 900–15 000; PDI = 1.12–1.23)) transformed from PM‐OHs in ≈ 100% conversion initiated ATRPs of styrene to construct PM‐b‐PS copolymers. The GPC traces indicated the successful extension of PS segment ( of PM‐b‐PS = 5 000–41 800; PDI = 1.08–1.23). Such copolymers were characterized by 1H NMR and DSC.
A series of well‐defined rod‐coil PAA‐b‐DPS block copolymers, containing Fréchet‐type dendronized polystyrene (DPS) with different generation as a rod‐like hydrophobic block and poly(acrylic acid) (PAA) as a hydrophilic coil were synthesized. The procedure included the following steps: the precursor PMA‐b‐DPS copolymer was prepared through ATRP of Fréchet‐type dendritic styrene macromonomer bearing the first to the third generation (G1–G3), respectively, initiated by poly(methyl acrylate) (PMA‐Br). Then, by converting PMA into PAA by subsequent hydrolysis, the targeted amphiphilic copolymers were obtained. Moreover, by using the rod‐coil amphiphiles as building blocks, large compound micelles and vesicles were formed in a binary solvent mixture of DMF/H2O. Morphological changes in self‐assembly showed dependence on the length of the dendronized block.
The preparation of associative networks containing multi‐walled carbon nanotubes (MWCNTs) with covalently attached cyclodextrin (CD) rings and poly[(isobutylene)‐co‐(maleic anhydride)‐co‐(maleic acid‐(4‐tert‐butylphenyl)amide)] in water is described in this study. The synthesis of CD containing MWCNTs is realized by an amidation reaction of oxidized MWCNTs with propargylamine followed by a 1,3‐dipolar cycloaddition with CD‐azide. Dispersion behavior indicated the high stability of these networks. An increase in viscosity compared to a solution of pure polymer as a cause of network formation is observed. The addition of a CD‐decomposing enzyme (taka‐diastase from Aspergillus oryzae) let the network collapse and results in sedimentation of the modified MWCNTs.
Summary: The phase behavior of poly(ethylene‐co‐styrene) (PES) and poly(ethylene‐co‐butene) (PEB) blends has been studied. A closed‐loop phase diagram was clearly observed in this weakly interacting system as the styrene content in the PES decreased to about 1 mol‐%. At higher styrene contents, the phase loop starts to interplay with the crystallization transformation at lower temperatures.
Phase diagram of PEB/PES blends. Phase boundary line is only for easy demonstration. 相似文献
A novel redox‐induced shape‐memory polymer (SMP) is prepared by crosslinking β‐cyclodextrin modified chitosan (β‐CD‐CS) and ferrocene modified branched ethylene imine polymer (Fc‐PEI). The resulting β‐CD‐CS/Fc‐PEI contains two crosslinks: reversible redox‐sensitive β‐CD‐Fc inclusion complexes serving as reversible phases, and covalent crosslinks serving as fixing phases. It is shown that this material can be processed into temporary shapes as needed in the reduced state and recovers its initial shape after oxidation. The recovery ratio and the fixity ratio are both above 70%. Furthermore, after entrapping glucose oxidase (GOD) in the system, the material shows a shape memory effect in response to glucose. The recovery ratio and the fixity ratio are also above 70%.
Well‐defined amphiphilic PCL‐b‐PDMAEMA block copolymers were successfully synthesized by a combination of ATRP and “click” chemistry following either a commutative two‐step procedure or a straightforward one‐pot process using CuBr · 3Bpy as the sole catalyst. Compared to the traditional coupling method, combining ATRP and click chemistry even in a “one‐pot” process allows the preparation of PCL‐b‐PDMAEMA diblock copolymers characterized by a narrow molecular weight distribution and quantitative conversion of azides and alkynes into triazole functions. Moreover, the amphiphilic character of these copolymers was demonstrated by surface tension measurements and critical micellization concentration was calculated.
