End-functionalized polymers by living cationic polymerization

Summary End-functionalized poly(isobutyl vinyl ether) (2) with a terminal amine, carboxylic acid, or ester group was prepared by quenching the HI/I₂-initiated living polymer ends with ring-substituted anilines (H₂N-C₆H₄-X, p or m; X = NH₂, COOH, COOC₂H₅). The living polymerization of isobutyl vinyl ether and the subsequent end-capping reaction were carried out at –15°C in methylene chloride. The resulting polymers exhibited a narrow molecular weight distribution and carried one terminal function (aniline residue) per chain, according to ¹H NMR structural analysis.     

Neutron Diffraction Study on the Structure of Na-Si-O-N Oxynitride Glasses

The local structure of a Na₂O─SiO₂ oxide glass and a Na₂O─iO₂─Si₃N₄ oxynitride glass has been investigated by the pulsed neutron diffraction method. In the oxide glass, the first peak of radial distribution function (RDF) curves appeared at 0.1627 nm corresponding to Si─O boxh length. In the oxynitride glass, the first peak of the RDF curve was shifted to longer distances at 0.1650 nm due to the coexistence of Si─O and Si─N boxhs. The first peak in the RDF curve of the oxynitride glass was deconvoluted into two peaks whose positions are located at 0.1626 and 0.1709 nm. The one at 0.1626 nm is ascribed to Si─O boxhs and the other at 0.1709 nm to Si─N boxhs. The number of silicon atoms around a nitrogen was found to be 2.42, suggesting that not all of the nitrogen atoms are boxhed to three silicon atoms, but 58% twofold (─N─) and 42% threefold (>N─) nitrogens coexist in the present Na-Si-O-N oxynitride glass. The formation of twofold nitrogens may arise from the reaction between ≡Si─O⁻ and ≡Si₃N groups. This model is compatible with the experimental observation that the density and Vickers hardness of oxynitride glasses increase with the nitrogen content.     

Living cationic polymerization of vinyl monomers by organoaluminium halides

Summary Living cationic polymerization of isobutyl vinyl ether was achieved by EtAlCl₂ in the presence of ethyl acetate at rather high temperatures up to +25°C in toluene. In the absence of the ester additives, neither living nor long-lived propagating species were formed under these conditions. Similarly, living propagating species of vinyl ethers with an ester unit in the pendant (2-vinyloxyethyl benzoate and methacrylate) were obtained with EtAlCl₂ alone. The obtained polymers showed a very narrow molecular weight distribution (¯M_w/¯M_n<1.2) and the ¯M_n was directly proportional to the monomer conversion.     

Preparation of Pd-Ag thin films by the RF-sputtering method and its catalysis for oxidative dehydrogenation of allylic alcohols

Pd-Ag thin films were prepared by the RF sputtering method on a Pyrex glass substrate to give monophasic alloys. Oxidation of allylic alcohols using the films gave selectively , -unsaturated carbonyl compounds in the presence of O₂; highly dispersed Pd species on Ag, Pd₇Ag₉₃ showed 95% selectivity for acrolein from allyl alcohol at 473 K.     

Living cationic polymerization of vinyl ethers with a functional group

Summary Vinyl ethers having oxyethylene units [CH₂=CHO-(CH₂CH₂O)-_nC₂H₅, n=1–4] were cleanly polymerized by the HI/I₂ initiator in a nonpolar solvent (toluene) at low temperatures (–15 and –40°C) to yield living-like polymers with a very narrow molecular weight distribution (Mw/Mn 1.2); the oxyethylene units in the monomers hardly disturbed the polymerization. The number-average molecular weight of the polymers increased proportionally to monomer conversion and the monomer-to-HI feed ratio. The polymerization rates of the (poly)ether-containing vinyl ethers were much greater than those of alkyl vinyl ethers under similar conditions, and it is presumed that the pendant ether oxygens intramolecularly activate the growing end. The polymers were soluble in methanol (with n1) and in water (with n2), depending on the number of oxyethylene units in the pendant.     

Living cationic polymerization of vinyl ethers with a functional group

Summary Living polymerizations of 2-vinyloxyethyl methacrylate and 2-vinyloxyethyl cinnamate were successfully performed with a mixture of hydrogen iodide and iodine (HI/I₂) as an initiating system in toluene at –15 to –40 °C, Although the two monomers have an unsaturated ester pendant group, their living polymerizations proceeded exclusively via the vinyloxyl group without undesirable side reactions of the pendant group. The product polymers had a very narrow molecular weight distribution (Mw/Mn 1.1), and {Mn} directly proportional to monomer conversion. For both vinyloxyethyl monomers, the addition of a new feed of monomer to a polymerization mixture led to an increase in polymer molecular weight which was again proportional to the conversion.     

Contact force detection on a minute aperture mounted optical contact slider using an acoustic emission sensor

Advances in the digital network society require both higher density and higher transfer rates in all sorts of storage systems. Especially in optical recording, the trend toward higher density and larger capacity requires novel surface-recording technologies that can drastically diminish head-to-medium spacing, resulting in an improvement in spatial resolution and, finally, a higher recording density. To this end, we have already proposed a novel contact optical head slider that is able to almost cancel the suspension load by generating hydrodynamic pressure, thus realizing a lower net contact force. Evaluating the dynamic contact force is requisite in realizing its stable sliding operation and higher signal readout performance. In this study, a continuous acoustic emission (AE) signal was utilized to detect the dynamic contact force. AE signal modulation was compared with the applied out-of-plane acceleration on a medium generated by a spindle combined piezo-electric actuator. It was clarified that the detected AE modulation amplitude was approximately proportional to the applied acceleration, and that utilizing AE modulation will be a useful method for evaluating dynamic contact force.