Dimensions of a free linear polymer and polymer immobilized on silica nanoparticles of a zwitterionic polymer in aqueous solutions with various ionic strengths

The dimensions and intermolecular interactions of a surface-grafted and unbound free polyampholyte, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), were estimated in aqueous solutions with various ionic strengths. Free linear PMPC was synthesized by atom-transfer radical polymerization (ATRP), and static light scattering (SLS) and dynamic light scattering (DLS) were carried out for the PMPC solutions with various concentrations of NaCl, c s. The hydrodynamic radius R H and the second virial coefficient A 2 of PMPC were independent of c s (0-0.5 M), though both R H and A 2 of polyampholytes usually strongly depend on the ionic strength. PMPC-immobilized silica nanoparticles (PMPC-SiNP) were also synthesized by surface-initiated ATRP, and DLS was carried out as for the solutions of linear PMPC to investigate the dependence of the dimensions of PMPC immobilized on a solid surface on the ionic strength. The molecular weight and surface density of PMPC immobilized on SiNP were estimated from the results obtained by GPC, NMR, and thermogravimetric analysis. The independence of R H of PMPC-SiNP was also observed, but its magnitude was larger than that of linear PMPC, although the molecular weight of PMPC immobilized on SiNP was smaller than that of linear PMPC. The larger dimension of PMPC immobilized on SiNP was explained by the excluded volume effect between the immobilized polymer chains.     

Photochemistry of naphthalimide photoacid generators

The photophysical properties of a series of 1,8-naphthalimide photoacid generators were studied by steady state fluorescence and phosphorescence spectroscopy. Emission and excitation anisotropies, triplet quantum yields in polar and nonpolar solvent and photoacid generation were evaluated. The singlet excited state exhibits a low polarity and is strongly deactivated by an efficient intersystem crossing process. In protic solvent, a homolytic singlet cleavage of the N-O bond occurs and leads to the acid production. The existence of a triplet state close to the singlet state was clearly evidenced. The presence of close singlet excited states is supported by fluorescence anisotropy and picosecond laser spectroscopy experiments. Results of DFT calculations well confirm the experimental contentions and yield important information about the cleavage process involved in such compounds.     

Poly(methyl methacrylate) grafted imogolite nanotubes prepared through surface-initiated ARGET ATRP

Poly(methyl methacrylate) grafted imogolite clay nanotubes were fabricated via activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) by designing a water-soluble amphiphilic ATRP initiator that can adsorb onto imogolite surface in an aqueous solution.     

Synthesis of TiO2 nanocoral structures in ever-changing aqueous reaction systems

A far-from-equilibrium strategy is developed to synthesize coral-like nanostructures of TiO(2) on a variety of surfaces. TiO(2) nanocoral structures consist of anatase base film and rutile nanowire layers, and they are continuously formed on substrates immersed in aqueous TiOSO(4)-H(2)O(2). The sequential deposition of TiO(2) starts with hydrolysis and condensation reactions of titanium peroxocomplexes in the aqueous phase, resulting in deposition of amorphous film. The film serves as adhesive interface on which succeeding growth of rutile nanowires to occur. This initial deposition reaction is accompanied by shift in pH of the reaction media, which is favorable condition for the growth of rutile nanocrystals. During the growth of rutile nanocoral layers, the amorphous base films are transformed to anatase phase. These sequential deposition reactions occur at temperatures as low as 80 °C, and the mild synthetic condition allows the use of a wide range of substrates such as ITO (indium tin oxide), glass, and even organic polymer films. The thickness of nanocoral layer is controllable by repeating the growth reaction of rutile nanocorals. TiO(2) nanocorals show photocatalytic activity as demonstrated by site-specific reduction of Ag(I) ions, which proceeds preferentially on the rutile nanowire layer. The rutile nanowire layer also shows photocatalytic decomposition of acetaldehyde, which is promoted upon increase of the thickness of the nanowire layer. The use of temporally transforming reaction media allows the formation of biphasic TiO(2) nanocoral structures, and the concept of nonequilibrium synthetic approach would be widely applicable to developing structurally graded inorganic nanointerfaces.     

Diffusion-weighted MRI for the detection of colorectal polyps: feasibility study

The purpose of this study was to determine the feasibility of diffusion-weighted magnetic resonance imaging (DWI) for detecting colorectal polyps. DWI (high b-value of 1000 s/mm²) was prospectively performed in 26 symptomatic patients who were scheduled to undergo colonoscopy. DWI and colonoscopic findings were interpreted in a blinded manner. The sensitivity and positive predictive value (PPV) of DWI for the detection of clinically relevant polyps (≥ 6 mm) and colorectal cancer (CRC) were calculated on a per-lesion basis, using colonoscopy results as the standard of reference. Sensitivity, specificity, PPV and negative predictive value (NPV) on a per-patient basis were also calculated. Sensitivity and PPV on a per-lesion basis were 80.0% [95% confidence interval (CI): 49.0%–94.3%] and 72.7% (95% CI: 43.4%–90.3%) for polyps ≥ 6 mm and CRC. Sensitivity, specificity, PPV and NPV on a per-patient basis were 85.7% (95% CI: 48.7%–97.4%), 84.2% (95% CI: 62.4%–94.5%), 66.7% (95% CI: 35.4%–87.9%) and 94.1% (95% CI: 73.0%–99.0%) for polyps ≥ 6mm and CRC. In conclusion, DWI cannot yet be recommended in a clinical setting in which DWI is performed first and subsequent colonoscopy is only performed in patients with positive findings at DWI. Further (technical) developments are required to increase its diagnostic yield.     

Program schedule: Symposium on statistical approaches to macromolecular systems in honor of Robert Simha

Abstract

Atomic force microscopy (AFM) has been applied to observe single-chain polymethylmethacrylate (PMMA) particles that were stored for six months at room temperature after being sprayed from very dilute solutions in good solvents, good/poor mixed solvents, and a theta solvent. Nearly monodisperse PMMA standards of molecular weights ranging from 7.90 × 10⁴ to 1.3 × 10⁶ were used to investigate the effect of molecular weight (MW) on the size of the single-chain PMMA particles. These single-chain particles showed close to spherical shapes. The morphology of single-chain PMMA particles of a given molecular weight has found to be identical in spite of different solvents used for solution spraying. Molecular weight dependence of the particle dimension was also found. The diameters of single-chain PMMA particles after correction of tip-geometry effect were compared with the values estimated from molecular weight and density.     

Characterization of catechol‐containing natural thermosetting polymer “urushiol” thin film

Urushi (oriental lacquer) is made from the sap of Rhus vernicifera and consists mainly of the catechol derivative urushiol. Thermal curing of urushiol, unlike other catechol derivatives, is possible because of the unsaturated double bonds in the long hydrocarbon side chain. We described here a simple, efficient method to produce a thermally cross‐linked urushi thin film using iron(II) acetate as the additive. The cured thin films showed robust, flexible feature as confirmed by strain‐induced elastic buckling instability for mechanical measurements (SIEBIMM) and bulging experiments. In contrast, a thin film of poly(dopamine) that is a typical catechol derivative without long hydrocarbon side chain showed brittleness. The long hydrocarbon side chain of urushiol plays an important role for both thermal processability and superior mechanical properties of the material. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3688–3692     

Gelation and adhesion behavior of mussel adhesive protein mimetic polymer

An acrylamide‐type copolymer containing catechol, amino, and hydroxyl groups was synthesized as a mimetic of the natural mussel adhesive protein (MAP). The obtained copolymer in a phosphate buffer solution (pH = 8.0) formed a hydrogel within 2 h under air, whereas gelation did not proceed under argon atmosphere. We confirmed that the cross‐linking reaction of the synthesized MAP mimetic copolymer was triggered by aerobic oxidation of catechol moieties to form an adhesive hydrogel. Two aluminum plates were adhered by the gelation of the MAP mimetic copolymer solution under humid air at room temperature. The interfacial region between the two aluminum plates failed at a lap shear strength of 0.46 MPa due to cohesive failure of the hydrogel. The adhesion strength was dominated by mechanical strength of the hydrogel as well as the interface interaction of catechol groups with substrate surface. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Broadband IP Stream Transmission Experiments over Global and Long Distance Networks

Super High Definition (SHD) movies were successfully transmitted as streaming contents at about 300 Mbps for the first time over a long distance IP network (more than 3,000 km), in conjunction with the experimental verification of traffic control and scalable multicast technologies.     

Simultaneous determination of a new gastrointestinal prokinetic agent (HSR-803) and its metabolites in human serum and urine by high-performance liquid chromatography using automated column-switching.

A method based on high-performance liquid chromatography using column-switching is described for the simultaneous determination of HSR-803 and its metabolites in human serum and urine. The system uses a six-port valve with a Nucleosil CN pre-column for on-line sample clean-up, and direct injection of samples. The limits of quantitation in serum and urine were 5 and 20 ng/ml for HSR-803 and 50 and 200 ng/ml for the metabolites, respectively. The coefficients of variation for the intra- and inter-day accuracies were between 0.8 and 7.1% for each compound. This method was applied to the pharmacokinetic studies in humans after oral administration of HSR-803.