Ikuyoshi Tomita

Electrochemically mediated atom transfer radical polymerization from a substrate surface manipulated by bipolar electrolysis: fabrication of gradient and patterned polymer brushes.

We report the first ever use of electrochemically mediated atom transfer radical polymerization (eATRP) employing a bipolar electrochemical method for the fabrication of both gradient and patterned polymer brushes. A potential gradient generated on a bipolar electrode allowed the formation of a concentration gradient of a Cu(I) polymerization catalyst through the one-electron reduction of Cu(II) , resulting in the gradient growth of poly(NIPAM) brushes from an initiator-modified substrate surface set close to a bipolar electrode. These polymer brushes could be fabricated in three-dimensional gradient shapes with control over thickness, steepness, and modified area by varying the electrolytic conditions. Moreover, by site-selective application of potential during bipolar electrolysis, a polymer brush with a circular pattern was successfully formed. Polymerization was achieved using both a polar monomer (NIPAM) and a nonpolar monomer (MMA) with the eATRP system.

Synthesis of novel organometallic polymers having metallacyclopentadiene moieties in the main chain by the reaction of diynes with (η5-cyclopetadienyl)bis(tripheylophospihne)cobalt complex

SummaryPolymerization reactions of η5-cyclopentadienyl)bis(triphenylphosphine)cobalt complex (2) and diyne monomers (3a-3c) were examined to obtain novel organometallic polymers bearing metallacyclopentadiene moieties in the main chain. When the polymerization reaction of 2 with 4,4′-bis(phenylethynyl)biphenyl (3a) was carried out in toluene at 50°C for 3days, an organometallic polymer having cobaltacyclopentadiene in the main chain was obtained quantitatively. The structure of the resulting polymer was confirmed by 1H-, 13C-NMR, IR, and UV spectra. The number-average molecular weight of the obtained polymer was evaluated as 9,600 (GPC, on the basis of polystyrene).

Design and synthesis of polymerizable cumulated double bond system. -Living coordination polymerization of alkylallenes by π-allylnickel catalyst-

Abstract The coordination polymerization of monoalkylallenes (2a; 1,2-nonadiene, 2b; 1,2-heptadiene, 2c; cyclohexylallene, 2d; t-butylallene) was carried out by [(π-allyl)NiOCOCF3]2 (1). The polymerization was found to proceed through a living process without any side reactions to yield soluble polymers in high yields, where the resulting polymers had predictable molecular weights and narrow molecular weight distributions. The coordination polymerization of dialkylallene (2e; 3-methyl-1,2-nonadiene, 2f; 2,3-nonadiene) was also carried out to obtain soluble polymers, although the polymerization rate of 2f was found to be considerably low compared with those of monoalkylallenes.

Arsole-Containing π-Conjugated Polymer by the Post-Element-Transformation Technique

A synthetic method to obtain an arsole-containing π-conjugated polymer by the post-transformation of the organotitanium polymer titanacyclopentadiene-2,5-diyl unit with an arsenic-containing building block is described. The UV/Vis absorption maximum and onset of the polymer were observed at 517 nm and 612 nm, respectively. The polymer exhibits orange photoluminescence with an emission maximum (Emax ) of 600 nm and the quantum yield (Φ) of 0.05. The polymer proved to exhibit a quasi-reversible redox behavior in its cyclic voltammetric (CV) analysis. The energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were estimated to be -5.43 and -3.24 eV, respectively, from the onsets for oxidation and reduction signals in the CV analysis. Further chemical modification of the arsole unit in the π-conjugated polymer by complexation of gold(I) chloride occurred smoothly resulting in the bathochromic shift of the UV/Vis absorption and lowering of the LUMO energy level.

Practical Synthesis and Properties of 2,5-Diarylarsoles

2,5-Diarylarsoles were easily synthesized from nonvolatile arsenic precursors. Diiodoarsine was generated in situ and reacted with titanacyclopentadienes to give 2,5-diarylarsoles. The structures and optical properties were studied in comparison with those of 2,5-diarylphosphole. It was found that the arsoles were much more stable in the air than the phosphole. Single crystal X-ray diffraction revealed the arsenic atoms adopted a trigonal pyramidal structure, reflecting on the s-character of the lone pair. The obtained 2,5-diarylarsoles and 2,5-diarylphosphole showed intense emission in solutions and solid state. In addition, the optical properties were controlled by transition-metal coordination.

Triblock copolymer-assisted synthesis of a hybrid mesoporous ethenylene–silica with 2D hexagonal structure and large pores

Highly ordered hybrid mesoporous ethenylene–silica is successfully synthesized from bis(triethoxysilyl)ethylene under acidic conditions using triblock copolymer P123 as a structure-directing agent. The mesoporous material is confirmed to exhibit a two-dimensional, hexagonal structure based on analyses by powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The material is also shown to have a uniform pore size distribution with a mean diameter of 6.3 nm, with a BET surface area of 705 m2 g−1 and pore volume of 0.84 mL g−1. The incorporation of ethenylene groups within the silicate framework is confirmed by solid-state nuclear magnetic resonance (NMR) measurements, and the formation of an organic–inorganic network composed of the O1.5Si–CHCH–SiO1.5 unit is strongly suggested by 13C and 29Si NMR analyses. Quantitative analysis of the available ethenylene content by liquid-phase bromination followed by iodometric titration indicates that approximately 20% of the constituent ethenylene is exposed at the surface and available for chemical reaction.

A novel polyaddition of bifunctional acetylenes containing electron-withdrawing groups: 4. Synthesis of polymers having enone moieties by the reaction of ynones with bifunctional heteronucleophiles

Abstract Phosphine-catalysed polyaddition of bifunctional ynones with diols or with dithiols is described. By the tri- n -butylphosphine-catalysed polyaddition of aromatic bis(ynone) having benzene ring as a spacer (without methylene group adjacent to carbonyl groups) or aliphatic bis(ynone) having octamethylene group as a spacer with p -xylene glycol, polymers having β-alkoxyenone moieties in the main chain were obtained in high yield. The polyaddition of the aromatic bis(ynone) gave a polymer composed of specifically E -unit, while that of the aliphatic bis(ynone)s produced a polymer containing both E - and Z -units. Further, the polyaddition with dithiols with bifunctional ynones was also carried out under similar conditions to yield the corresponding polymer composed of both E - and Z -units in almost quantitative yield.

Facile Synthetic Method for the Preparation of Dithioacetals by the Double Conjugate Addition of Acetylenes Bearing Electron-Withdrawing Groups with Thiols

Abstract β, β-Bis(alkylmercapto)propionates were obtained by the reaction of methyl propiolates with 2 equiv. of mercaptanes in the presence of tri-n-butylphosphine in high yield. The corresponding dithioacetals could be also obtained by the conjugate addition of mercaptanes toward methyl β-alkylmercaptoenoates, in which, tri-n-butylphosphine also catalyzed the addition of thiols.

Reaction of organocobalt polymers with isocyanide. Synthesis of novel poly[(η5-cyclopentadienyl)(η5-amino-cyclopentadienyl)cobalticinium-diyl-alt-biphenyl-4,4′-diyl)]s

Abstract On the basis of the fact that the reaction of a cobaltacyclopentadiene derivative with t -butyl isocyanide quite effectively provides a (η 5 -cyclopentadienyl)(η 4 -iminocyclopentadiene)cobalt derivative which reveals a unique solvatochromic behavior, the polymers having cobaltacyclopentadiene-diyl and biphenyl-4,4′-diyl repeating units 1 were subjected to the reaction with t -butyl isocyanide to give those having (η 5 -cyclopentadienyl)(η 4 -iminocyclopentadiene)cobalt moieties in the main chain 2 . By the subsequent reaction with iodomethane, the polymers 2 were converted quantitatively into cobalticinium-containing polymers 3 (i.e. poly[(η 5 -cyclopentadienyl)(η 5 -amino-cyclopentadienyl)cobalticinium-diyl- alt -biphenyl-4,4′-diyl)]s). The results of the spectroscopic, the electrochemical, and thermal analyses of the polymers ( 2 and 3 ) are also described.

Three-component coupling polymerization of bisallene, aryl dihalides, and nucleophiles via π-allylpalladium complex. II. Effect of nucleophiles on polymerization

A novel palladium-catalyzed three-component polycondensation of 1,2,10,11-dodecatetraene, 4,4′-diiodobiphenyl, and nucleophiles was carried out using various carbanions and amines as a nucleophilic part. The polymerization with various sodium diethyl malonates produced polymers in high yields. Particularly, no exo-double bond was detected in the polymers prepared from sodium diethyl malonates bearing substituents directly on the carbanion center. The ratios of E- and Z- isomeric units in the polymers were dependent on the structure of the nucleophiles used. Other carbanions with appropriate electron-withdrawing groups such as sulphones and ketones can be also used as a nucleophile for the present polycondensation. Within heteronucleophiles examined, cyclic amines were suitable to produce polymers in high yields.