Articles in 2015

The anti-fouling character of polymer brushes against marine organisms was investigated by performing settlement tests with barnacle cypris larvae and mussel larvae in their adhesion period, as well as a marine bacteria colonization test. The surface charge and hydration state in saline seawater appear to be important factors in the versatile anti-fouling performance of zwitterionic polyelectrolyte brushes.

Susceptible situation of water molecules in the vicinity of lopsidedly charged copolymer films (upper) and a zwitterionic copolymer film. The charge-neutralized polymer surface is less perturbative to the structure of vicinal water. The image first published in Kobunshi 39, 445 (Hot Topics) (2014).

Because of importance of anions as analyte in diverse fields, a reliable and practical method that allows simple and rapid anion detection has been in increasing demand. To satisfy this requirement, many efforts have been made to develop optical anion sensor materials for sensor applications. This article reviews recent progress in the design and fabrication of conjugated polymer-based anion sensors. Through rational molecular design of the sensor polymers, certain structures have been found to possess desirable anion detection abilities, including enhanced binding affinity, strict size specificity and applicability to anions in an aqueous environment.

The alternating and random low band gap conjugated copolymers with dialkyloxy flanked-dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene derivatives (DTBDTs) as electron donor moieties and 5,6-di(dodecyloxy)-2,1,3-benzothiadiazole (BT) were first synthesized and characterized. As compared with the alternating copolymers, the solubility and molecular weight of the random copolymer was clearly increased. Power conversion efficiencies (PCEs) of 2.41, 3.15 and 4.73% have been achieved in the photovoltaic cells (PVCs) from the random copolymer.

This Focus Review provides an overview of our recent study and related work on ion conductive polymer nanofibers and their applications in polymer electrolyte fuel cells. We succeeded in evaluating the intrinsic proton and anion conductivity of electrospun nanofibers and revealed their distinguished ion conductive properties, which were quite different from those of the corresponding polymer membranes. These ion conductive nanofibers have potential utility as polymer electrolyte composite membranes to improve fuel cell performance by utilizing efficient ion conduction both inside and at the surfaces of nanofibers.

The dimensions of the amorphous and crystalline layers in PHB and PHB/DGEBA blends crystallized at different temperatures were obtained from SAXS measurements at different temperatures. Interlamellar segregation of DGEBA was observed for DGEBA content lower than 30%. The role of the rigid amorphous fraction was determined to be preponderant in the behavior of the amorphous and crystalline dimensions as a function of the temperature.

poly(N-isopropylacrylamide-co-acrylamide) copolymer-coated La_0.73Sr_0.27MnO₃ nanoparticles were prepared through admicellar polymerization. The prepared nanoparticles with core-shell can be used as heat-generating agent in magnetic hyperthermia therapy.

This review focuses on redox-induced molecular actuation in macromolecular and self-assembled systems. Effective amplifications of conformational changes of unit molecular part are explored on the basis of three categories: polymeric system; molecular interactions; and self-assembled system. The importance of highly ordered structures is suggested to effectively amplify conformational change of small molecular unit into macroscopic deformation of bulk materials. Finally, future outlook toward electrochemical soft actuators and tips to prepare stimuli-responsive molecular assemblies, which undergo amplification in conformational change of constituent molecules, are provided.

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.

Propagation of neural progenitor cells on silk-based macroporous scaffolds. The potential for macroporous 3D silk fibroin scaffolds for the propagation of human neural progenitor cells is investigated. It is found that microstructure and porosity of the fabricated silk fibroin scaffolds allow for sustained viability and proliferation of human neural progenitors. We also find that although fibroin scaffolds from mulberry and non-mulberry silks are cytocompatible, non-mulberry silk matrices appeared to promote slightly increased cell proliferation and matrix deposition.

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.

The establishment of a Lewis acid-mediated selective propoxylation reaction using a specific borane catalyst enabled the synthesis of a novel class of PPG with an increased primary hydroxyl content of up to 70%. In addition, we developed a high yielding continuous process for producing the new PPG with a low amount of by-products by using tube reactors combined with film evaporators for by-product removal. Our new PPG achieves an excellent balance between reactivity and humidity resistance. As a result, it has important advantages for a broad area of polyurethane applications.

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.

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.

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 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 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.

Single-chain crosslinked star polymers with hydrophilic and thermoresponsive poly(ethylene glycol) short arms and a hydrophobic core were created as novel microgel star polymers of single polymer chains via the intramolecular crosslinking of self-folding amphiphilic random copolymers in water. For this, well-controlled amphiphilic random copolymers bearing hydrophobic olefin pendants were synthesized as self-folding precursors by ruthenium-catalyzed living radical polymerization and the subsequent introduction of olefin units. The copolymers with 20–40 mol% hydrophobic units efficiently gave single-chain crosslinked star polymers in water.

In this work, we newly prepared the multi-walled carbon nanotube (MCNT)-grafted poly(N-isopropylacrylamide) (PNIPAM) on their termini. After grafting PNIPAM, MCNTs dispersed well into water. In addition, the synthesized PNIPAM-terminated MCNTs (PNIPAM-MCNTs) were blended with poly(vinylalcohol) (PVA), and a hybrid film was prepared. The hybrid film showed bending actuation in response to infrared laser due to the heat generated by MCNTs.