Research articles

The cellulose derivatives bearing pyridyl and bipyridyl residues were synthesized, and their recognition abilities as chiral stationary phases for high-performance liquid chromatography were evaluated. Among them, the cellulose derivatives with regioselective substitution of bipyridyl residues exhibited a relatively high chiral recognition. The recognition ability of the derivatives was significantly influenced by the coordination of a Cu(II) ion to the bipyridyl residues. In addition, the derivatives were also used for the ligand-exchange chromatography with an eluent containing a copper salt in order to directly separate amino acids without derivatization.

A method to evaluate both the growth rate and the number of spherulites effectively growing with time at constant temperature is shown for a polyoxymethylene copolymer (POMC). It consists in following the development of the crystallinity with time by differential scanning calorimetry and in estimating the maximum radial dimension of coalesced spherulites in the crystallized sample by scanning electron microscopy. The method is applicable to any linear polymer to obtain information on the nucleation and growth processes.

A series of novel fluorinated crosslinkable poly(phthalazinone ether)s, bearing tetrafluorostyrene groups (FSt-FPPEs), have been prepared by polycondensation. The structures were identified using ¹H-NMR and infrared spectroscopy measurements. The resulting polymers could be thermally crosslinked either at 160 °C in the presence of a free radical initiator dicumyl peroxide under vacuum or at 280 °C in the absence of any initiator under vacuum. The refractive indices of the crosslinked polymers could be well controlled over a wide range; crosslinked polymers also show low optical losses at 1550 nm. These results indicate that the application of FSt-FPPE in the field of optical waveguide seems feasible and promising.

Three types of poly(4-diphenylaminostyrene) (PDAS) having different polymer chain structures were prepared by living anionic polymerization, and the electroluminescence of PDAS/tris(8-hydroxyquinoline) aluminum (Alq₃) blend films was examined. The hole drift mobility of PDAS increased with an increase in the syndiotactic configuration. The current density, turn-on voltage and brightness were also improved with an increase in the syndiotactic configuration of PDAS.

Poly(tetramethylsilarylenesiloxane) derivatives having diphenylfluorene (P1) or diphenyldibenzosilole (P2) skeleton were synthesized. The excellent thermal stability of P1 and P2 was confirmed by the differential scanning calorimetry and thermogravimetry. There were differences in the crystallinity between P1 and P2. The fluorescence quantum yield of P2 was higher than those of P1 and the corresponding monomer indicating the decrease in the tendency toward aggregation by use of dibenzosilole skeleton.

By the presence of 100 W ultrasound during extrusion, SiO₂ nanoparticles become smaller and their aggregations disappear, indicating that more homogeneous dispersion of SiO₂ nanoparticles into propylene-based copolymer matrix is achieved.

Polyvinyl alcohol (PVA), which has been used to prevent flaking of paint pigments on traditional Japanese Shohekiga, became white and we investigated its phenomenon. The surface of whitened PVA was irregular and rugged, and many micrometer size cracks were observed. This suggests that efficient scattering of all visible region light from the cracks causes whitening. Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy measurements revealed that interchain dehydration and chemical crosslinking (C–O ether linkage) occurred on the surface of whitened PVA.

Dendritic multiarm star block copolymer hyperbranched poly(glycidol)–poly(N-isopropylacrylamide) (HPG–PNIPAM) was prepared by the reversible addition-fragmentation transfer polymerization technique. In aqueous solution, the unimolecular polymeric micelles HPG–PNIPAM have a core-shell nanostructure, with hydrophilic HPG as the core and thermoresponsive PNIPAM as the shell. Dynamic and static laser light scattering measurements show a unimolecular process of reversible phase transition behavior for the unimolecular polymeric micelles in dilute solution.

In the free-radical cross-linking multiallyl polymerization, the structure of network polymer precursor (NPP) consisting of oligomeric primary polymer chains would become core-shell type dendritic or nanogel-like with the progress of polymerization and then, the NPPs can collide with each other to form cross-links among NPPs, eventually leading to gelation. Thus, the dilution of NPP by newly adding monomer could prevent the cross-link formation between NPPs and consequently, lead to the successive growth of NPP from nanogel to microgel.

Polyethylene glycol-containing hematin (PEGylated hematin) was prepared using the Mitsunobu reaction as a water-soluble biomimetic catalyst for polymerization of arbutin in a phosphate buffer solution of pH 7.0. The structure of polyarbutin obtained was characterized by ¹H nuclear magnetic resonance and infrared spectroscopy. PEGylated hematin showed high catalytic activity for arbutin polymerization, indicating that it is a better catalyst compared with horseradish peroxidase.

Oligothiophene-stacked polymers were synthesized by the Suzuki–Miyaura coupling reaction. Oligothiophene units were layered in proximity, ∼3.0 Å from each other. The polymers were characterized by various spectroscopic and electrochemical methods. The polymers have potential application to optoelectronic devices such as hole-transporting materials.

The polymer graded index (GRIN) lens with high impact resistance can be made by easy technique, but the thermal stability is not so excellent. In this study, we propose a new method of fabricating organic–inorganic microcomposite cylindrical GRIN lens. This method is based on spontaneous frontal polymerization technique and diffusion of two organic materials with different refractive indices to an inorganic wet-gel. The obtained microcomposite cylindrical GRIN lenses are not only thermally stable, but also have a controlled refractive index profile due to its inorganic matrix.

Binary catalysts composed of cationic rhodium complexes, [(tfb)Rh(L)₂]X (tfb: tetrafluorobenzobarrelene, L: phosphine ligand, X: counter anion), and ⁱPrNH₂ induced living polymerization of phenylacetylene and its ring-substituted derivatives. The living nature was confirmed by kinetic plots of the polymerization. Nuclear magnetic resonance studies revealed that ⁱPrNH₂ serves to dissociate the coordinating PPh₃ ligand of [(tfb)Rh(L)₂]X to form an initiating species. Block copolymers were synthesized by the sequential polymerization of different phenylacetylenes using the present catalyst.

Recently, polymer matrix-based nanocomposites have become a prominent area of current research and development in optics, optoelectronic, biomedical, electrical and electronic applications. Organic polymer-based electronic devices offer the potential for lower cost and more flexible manufacture but need significant improvements in both efficiency and long-term stability. Therefore, we have made an attempt to synthesize polyaniline (PANI)–zinc oxide (ZnO) using chemical and emulsion polymerization techniques. The properties of ZnO–PANI films were then systematically characterized with several physical techniques. The electrochemical investigations revealed that the individual redox properties of ZnO and PANI can be maintained in a nanocomposite ZnO–PANI system. Further, results indicated that ZnO–PANI films could exhibit a wide potential window. Moreover, we have observed the formation of a single-layer nano-Schottky junction in the ZnO–PANI film, and interesting positive temperature coefficient properties in ZnO–PANI.

Addition-type poly(norbornene)s with siloxane substituents were synthesized using the (η³-Allyl)(η⁵-cyclopentadienyl)palladium/tricyclohexylphosphine/[Ph₃C][B(C₆F₅)₄] system. The obtained polymers had very high glass transition temperature of up to 255 °C, and their films displayed high mechanical flexibility. The incorporation of siloxane groups in the chain resulted in significant increase in the gas permeability of their films, and the polymers with branched siloxane groups showed high oxygen permeability (P(O₂)=66–360 Barrer). In addition, poly(norbornene) membranes with a unique porous structure were prepared.

Novel thermal iniferter, synthesized from 1,1,2,2-tetraphenyl-1,2-ethanediol and α-bromoisobutyryl bromide, was used to polymerize styrene and methyl methacrylate through controlled radical polymerization (CRP) mechanism.

The scanning electron microscope images show how the pore diameter is changing as the time of thermal treatment is increasing. In the graphic, one can appreciate the oscillatory behavior of the pore size and the fitting curve obtained when the mathematical model is applied to the experimental data.

Hyperbranched polysiloxanes were synthesized by polyhydrosilylation of silsesquioxane derivatives and vinyl derivatives in the presence of Karstedt's catalyst. The obtained hyperbranched polymers were soluble in common solvents and exhibit good thermal stability. The refractive index values of the obtained polymers tend to decrease with increasing structure size of co-monomers.

The synthesis and photo-polymerization of hyperbranched polyesters containing pendant methacryloyl groups (HBPE-MA) were examined. Polycondensations of 1,4-bis(chloromethyl)benzene (BCMB) with 1,3,5-benzenetricarboxylic acid (BTCA) proceeded very smoothly to give the soluble hyperbranched polyesters (HBPE) in satisfactory high yields using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Furthermore, HBPE-MA was synthesized by the reaction of HBPE with methacrylic acid (MAA) by the DBU method. The photo-induced radical polymerization of HBPE-MA was performed in the presence of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one (Irgacure 907) as a photoinitiator in the film state upon UV irradiation to afford the insoluble cured film.