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Precise synthesis of dendrimer-like star-branched polymers, a novel class of structurally well-defined hyperbranched polymers, by stepwise iterative methodologies based on the ‘arm-first’ divergent approach is described. The methodologies basically involve a linking reaction of chain-functionalized living anionic polymer(s) and a transformation reaction to regenerate the next reaction sites. By repeating the two reaction steps, high-generation and high-molecular-weight dendrimer-like star-branched polymers and their block copolymers were successfully synthesized. The resulting polymers were characterized by small-angle X-ray scattering, viscosity and atomic force microscopy measurements to estimate their sizes, shapes and solution behavior.
Polyelectrolyte multilayers-modified membrane filter, leading to achieve rapid immunoassay as compared with the conventional enzyme-linked immunosorbent assay (ELISA) system. The antigen–antibody reaction was carried out by the centrifugal permeation of antigen solution allowing the local condensation of the antigen molecules in the proximity of the primary antibody. Hence, the incubation time for the antigen–antibody reaction was just permeation time, 3 min, which overcomes the molecular diffusion as rate-limiting factor compared with conventional ELISA method.
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.
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.
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.
Cocrystallization phenomenon between the deuterated (D) and hydrogenated (H) species of a series of polyoxymethylene blends with various H/D ratios has been established on the basis of the detailed analysis of thermal and infrared (IR) spectral data. The melting and crystallization temperatures were found to shift continuously toward higher temperature side, with an increase of the D content. The IR spectra were found to change remarkably depending on the H/D blend content. These continuous changes have been interpreted reasonably by assuming the random arrays of the H and D chains in the crystal lattice.
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.
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.
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.
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.
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.
To increase the tenacity of poly L-lactic acid (PLLA), we have developed self-assembling siloxane nanoparticles with three phases: a high-density crosslinked siloxane phase (plural cores), an elastomeric silicone phase and a caprolactone oligomer phase with a high affinity for the PLLA matrix. These nanoparticles self-assemble by aggregation and condensation of an organosiloxane with three units, which respectively form each phase. Adding the nanoparticles (5 wt%) to PLLA improved the tenacity (elongation) of the PLLA without degrading its high breaking strength.
