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This review describes the N-heterocyclic carbene-catalyzed transformations of Michael acceptors that were developed by our research group, including (1) tail-to-tail dimerization of a wide variety of substrates, such as vinyl pyridines, acrylates, methacrylates and methacrylonitrile, (2) cyclotetramerization of acrylates to form trisubstituted cyclopentenones, (3) tandem oxa-Michael addition and head-to-tail dimerization of methacrolein and (4) oxa-Michael addition polymerization of hydroxyl-functionalized acrylates.
The segmental mobility of polymers at the interface contacted with air, a liquid and a solid is much different from that in the internal bulk phase. This review summarizes the recent studies offering a concept that the polymer interface is a useful medium for functionalization of solid polymer materials.
Bio-based polyureas (PUs) are prepared by the polyaddition of a multifunctional bio-photodimer 4,4'-diamino-α-truxillic acid having two amines and two carboxyls with an aromatic isocyanate comonomer. The films of PUs show high transparency and swell in the alkaline solution when the PU carboxyls are anionized. If metal nitrate salts are added to the films, mechanical properties are increased by the double interaction of the metal cation with carboxylate and nitrate with urea, which causes the films to change the color.
New D-A-conjugated polymers with disilanobithiophene as the donor were synthesized and their optical and electrochemical properties and applications to bulk heterojunction polymer solar cells were investigated.
A tetra-arm diblock copolymer, consisting of tetra-PEG as central block and random copolymer of N-isopropylacrylamide (NIPAm) and 4-phenylazophenyl methacrylate (AzoMA) as four end blocks, exhibit high-temperature unimers and low-temperature micelles in a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6). The upper critical micellization temperature depends on photoisomerization states of azobenzene in the copolymer. Photoinduced unimer/micelle transition was reversible at a suitable temperature.
The modulation of interparticle distances in aggregates of gold nanoparticles by light irradiation is described. Stable aggregates of a series of imidazolium-presenting gold nanoparticles were obtained via a photo-responsive mono-carboxylate linker. By irradiating the aggregates with ultraviolet, the photo-responsive linker was transformed, leading to the generation of another carboxyl group. As a result, the gold nanoparticles were tightly bound via the dicarboxylate linkers. These changes decreased the interparticle distances in the aggregates, as verified by microscopic observations, and can induce significant changes in their optical characteristics.
A new conjugated poly(pyridinium salt)s derivative (P1) containing heterocyclic phenathridine moieties in the main chain was prepared by ring-transmutation polymerization reaction. Its interaction with calf thymus DNA (ctDNA) in aqueous ethanol solution was explored by means of UV-vis, fluorescence, circular dichroism (CD) spectroscopy, as well as dynamic light scattering (DLS) measurements.
We developed a facile and efficient material for mercury based on a polymer combining metal-complexation and acidic aqueous solution-soluble groups. Because the polymer is soluble in acidic aqueous solution, the metal-complexation proceeds homogeneously and efficiently. As metal complexation progresses, cross-linking takes place between the metal-complexation groups and the metal ions, precipitating the polymer complex, which can be easily separated by filtration.
Polyhydroxyalkanoates (PHAs) are eco-friendly plastics that are synthesized by bacteria as an intracellular storage material. Ethanol is a key compound in molecular weight regulation of PHA during biosynthesis. In this study, three strains of Escherichia coli expressing PHA synthase (PhaCRe, PhaCAc or PhaCHe) were cultured to compare the effect of ethanol level on PHA molecular weight. As a result, it was revealed that PhaCAc tends to produce low molecular weight PHA due to its high ethanol sensitivity whereas PhaCHe produces high molecular weight PHA even in the presence of ethanol.
