Yoshinobu Tsujii

Synthesis of a well-defined glycopolymer by atom transfer radical polymerization

Controlled free radical polymerization of sugar-carrying methacrylate, 3-O-methacryloyl-1,2 : 5,6-di-O-isopropylidene-d-glucofuranose (MAIpGlc) was achieved by the atom transfer radical polymerization (ATRP) technique with an alkyl halide/copper-complex system in veratrole at 80°C. The time–conversion first-order plot was linear and the number-average molecular weight increased in direct proportion to the ratio of the monomer conversion to the initial initiator concentration, providing PMAIpGlc with a low polydispersity. The sequential addition of the two monomers styrene (S) and MAIpGlc afforded a block copolymer of the type PS-b-PMAIpGlc. The acidolysis of the homo- and block copolymers gave well-defined glucose-carrying water-soluble polymers PMAGlc and PS-b-PMAGlc, respectively. The amphiphilic PS-b-PMAGlc block copolymer exhibited a microdomain surface morphology with spherical PS domains in a PMAGlc matrix.

Controlled grafting of a well-defined polymer on a porous glass filter by surface-initiated atom transfer radical polymerization

Abstract The atom transfer radical polymerization (ATRP) technique using the copper halide/sparteine complexes was applied to the graft polymerization of methyl methacrylate on a porous glass filter on which the initiator, 2-(4-chlorosulfonylphenyl) ethyltrichlorosilane, was immobilized by chemisorption. The graft chains were cleaved from the glass filter by the HF treatment in the presence of a phase transfer catalyst. Gel permeation chromatographic and infrared absorption spectroscopic measurements confirmed that the polymerization carried out in the presence of the free (sacrificing) initiator, p-toluenesulfonyl chloride, afforded a graft layer of well-controlled, low-polydispersity polymer on the inner surface of the porous glass filter. The number-average molecular weight (Mn) of the graft polymer increased with reaction time, and it was nearly equal to the Mn of the free polymer produced in the solution. The graft density on the inner surface of the porous glass filter was as high as those formed on a silicon wafer and a silica particle under similar conditions.

Novel Solid‐State Polymer Electrolyte of Colloidal Crystal Decorated with Ionic‐Liquid Polymer Brush

Much attention has been directed toward polymeric and ionicliquid (IL) electrolytes and their composites for improving the safety in energy devices including lithium-ion rechargeable batteries (LIBs), electric double layer capacitors, and dye-sensitized solar cells. [ 1–4 ] For practical use, however, the most serious problem is that ionic conductivity is greatly spoiled. Here, we show an entirely new concept for fabricating a leakand vapor-free, non-fl ammable, and solid electrolyte with a highly ion-conductive network channel. This was fi rst achieved by three-dimensional, regular self-assembly in a crystal of hybrid silica particles (PSiPs) with an IL-type of concentrated polymer brushes (CPBs) in the presence of a small amount of IL, hence providing a polymer-brush domain that is continuously connected as a network channel and enhances the ion conduction by coupling with the segmental motion. This is completely different from the previously reported electrolyte reinforced with nanoparticles, which are in an amorphous state but not in a crystal. The strategy is based on our recent achievements involving the CPB and IL. First, by surface-initiated living radical polymerization (surface-initiated LRP), we succeeded in exceptionally densely grafting well-defi ned polymers on a solid surface to produce a well-defi ned CPB and found that it showed properties including high modulus, super lubrication, and unique size exclusion that were quite different and even unpredictable from those of the previously studied semidilute polymer brushes (SDPBs). [ 5 ] Second, we demonstrated that a solvent suspension, which is liquid but not solid, of monodisperse silica particles (SiP) with the CPB of poly(methyl methacrylate) (PMMA) formed a new type (semisoft type) of colloidal crystal; [ 6 ] unlike the previously known (soft and hard) colloidal crystals, the driving

Fabrication of Contrast Agents for Magnetic Resonance Imaging from Polymer-Brush-Afforded Iron Oxide Magnetic Nanoparticles Prepared by Surface-Initiated Living Radical Polymerization

The aim of this study is to fabricate a contrast agent for magnetic resonance imaging (MRI) by using hybrid particles composed of a core of iron oxide magnetite (Fe3O4) nanoparticles and a shell of hydrophilic polymer brush synthesized by surface-initiated (SI) living radical polymerization. To achieve this, Fe3O4 nanoparticles were surface-modified with initiating groups for atom transfer radical polymerization (ATRP) via a ligand-exchange reaction in the presence of a triethoxysilane derivative having an ATRP initiation site. The ATRP-initiator-functionalized Fe3O4 nanoparticles were used for performing the SI-ATRP of methyl methacrylate to demonstrate the ability of the synthesized nanoparticles to produce well-defined polymer brushes on their surfaces. The polymerization proceeded in a living fashion so as to produce graft polymers with targeted molecular weights and narrow molecular weight distribution. The average graft density was estimated to be as high as 0.7 chains/nm(2), which indicates the formation of so-called concentrated polymer brushes on the Fe3O4 nanoparticles. Dynamic light scattering and transmission electron microscope observations of the hybrid nanoparticles revealed their uniformity and dispersibility in solvents to be excellent. A similar polymerization process was conducted using a hydrophilic monomer, poly(ethylene glycol) methyl ether methacrylate (PEGMA), to prepare Fe3O4 nanoparticles grafted with poly(PEGMA) brushes. The resultant hybrid nanoparticles showed excellent dispersibility in aqueous media including physiological conditions without causing any aggregations. The blood clearance and biodistribution of the hybrid particles were investigated by intravenously injecting particles labeled with a radio isotope, (125)I, into mice. It was found that some hybrid particles exhibited an excellently prolonged circulation lifetime in the blood with a half-life of about 24 h. When such hybrid particles were injected intravenously into a tumor-bearing mouse, they preferentially accumulated in the tumor tissues owing to the so-called enhanced permeability and retention effect. The tumor-targeted delivery was visualized by a T2-enhaced MRI measurement.

Near-infrared charge resonance band of intramolecular carbazole dimer radical cations studied by nanosecond laser photolysis

Abstract The absorption of the charge resonance (CR) bands of dimer radical cations of meso- and rac-2,4-di(N-carbazolyl)pentanes (m- and r-DCzPe), and trans-1,2-di(N-carbazolyl)cyclobutane (DCzBu) was observed by nanosecond laser photolysis. The band peaks for m-DCzPe, r-DCzPe and DCzBu appeared around 1600, 1800 and 2000 nm, respectively. The peaks were shifted to shorter wavelengths with increasing overlapping of two carbazole chromophores. That is, the band gap of the CR band becomes larger with increasing interaction with the neighboring chromophore.

Blood Clearance and Biodistribution of Polymer Brush-Afforded Silica Particles Prepared by Surface-Initiated Living Radical Polymerization

The physiological properties of polymer brush-afforded silica particles prepared by surface-initiated living radical polymerization were investigated in terms of the circulation lifetime in the blood and distribution in tissues. Hydrophilic polymers consisting mainly of poly(poly(ethylene glycol) methyl ether methacrylate) were grafted onto silica particles by surface-initiated atom transfer radical polymerization that was mediated by a copper complex to produce hairy hybrid particles. A series of hybrid particles was synthesized by varying the diameter of the silica core and the chain length of the polymer brush to examine the relationship between their physicochemical and physiological properties. The hybrid particles were injected intravenously into mice to investigate systematically their blood clearance and body distribution. It was revealed that the structural features of the hybrid particles significantly affected their in vivo pharmacokinetics. Some hybrid particles exhibited an excellently prolonged circulation lifetime in the blood with a half life of ∼20 h. When such hybrid particles were injected intravenously into a tumor-bearing mouse, they preferentially accumulated in tumor tissue. The tumor-targeted delivery was optically visualized using hybrid particles grafted with fluorescence-labeled polymer brushes.

Synthesis of a well-defined anthracene-labelled polystyrene by atomtransfer radical polymerization

The atom-transfer radical polymerization of styrene was carried out in bulk at 110°C with a newly synthesized bromine-containing anthracene derivative, 9,10-bis(1-bromoethylcarbalkoxymethyl)anthracene (ANTDBr), as a bifunctional initiator and a cuprous bromide complex Cu(I)Br/2dHbipy (dHbipy = 4,4′-di-n-heptyl-2,2′-bipyridine). g.p.c. and n.m.r. studies revealed that the initiation efficiency of ANTDBr is 100% and the polymerization proceeds in a controlled fashion, providing low-polydispersity polystyrenes with one anthracene chromophore in the middle of the main chain. This success opens up a new route to well-defined anthracene-labelled polymers including random and/or block copolymers, which will be useful as probe polymers to study, e.g., local chain dynamics by the fluorescence depolarization technique.

Lubrication mechanism of concentrated polymer brushes in solvents: effect of solvent viscosity

We investigated the frictional properties of concentrated polymer brushes (CPBs) of poly(methyl methacrylate) (PMMA) immersed in two highly viscous ionic liquids (ILs) that are good solvents for PMMA: N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI). These ILs could swell the CPB of PMMA to the same degree as toluene, a more commonly used good solvent of much lower viscosity. The CPB of PMMA effectively reduced the interaction between surfaces in these ILs and hence developed otherwise hidden hydrodynamic lubrication, which was characterized by the dependence of the frictional coefficient μ on shear velocity v. In the hydrodynamic-lubrication regime, the linear relationship was obtained between them in the double logarithmic plot, giving a slope close to unity, which is expected for a Newtonian fluid, in the solvents studied even though the viscosity differed by nearly two orders of magnitude. More interestingly, the μ values in this regime of lubrication were found to be scaled by the viscosity of the solvent. These results not only enable us to discuss the details of the effect of solvent viscosity on lubrication properties of the CPB systems but also demonstrated their ability to act as an excellent lubrication system in combination with ILs as lubricating fluids.

A trough with radial compression for studies of monolayers and fabrication of Langmuir-Blodgett films

Abstract A new type of Langmuir trough with radial compression is reported for studies of monolayer properties and fabrication of Langmuir-Blodgett (LB) films. The trough included twenty curved diaphragms, which form a circular shape on water and compress monolayers. Typical monolayers of arachidic acid, DL-α-phosphatidylcholine dipalmitoyl, cellulose tridecanoate, and poly (butyl methacrylate) showed reproducible surface pressure-area isotherms with radial compression. Flow profiles were studied of monolayers on cellulose tridecanoate and poly(butyl methacrylate) and suggested that the monolayers are radially compressed with no particular film disturbance. A Wilhelmy glass plate preserved no deflection in the subphase surface from low to high surface pressures during the film compression and decompression; no pressure excess causing the deflection, which is frequently observed in the case of the film compression with a sliding barrier, was found on both sides of the Wilhelmy plate. Application of the radial compression enabled to do a symmetrical deposition for the fabrication of LB films.

Immobilization of semisoft colloidal crystals formed by polymer-brush-afforded hybrid particles

An immobilization technique for semisoft colloidal crystals, which are ordered arrays of polymer-brush-afforded hybrid particles synthesized by surface-initiated living radical polymerization (SI-LRP), is reported. Silica particles were first grafted with well-defined block copolymers of poly(methyl methacrylate-co-hydroxyethyl methacrylate)-b-poly(methyl methacrylate), P(MMA-co-HEMA)-b-PMMA by SI-LRP, which gave a graft density as high as 0.7 chains/nm(2). The HEMA units reacted with 2-isocyanatoethyl methacrylate to introduce vinyl groups at the outer layer of the polymer-brush shell. The modified hybrid particles formed a colloidal crystal in a solution containing a small amount of free polymers with vinyl groups. The colloidal crystal was photoirradiated in the presence of a photoradical initiator to immobilize it through a cross-linking reaction among the vinyl groups. The structural analyses of the colloidal crystals before and after the photoirradiation were carried out by confocal laser scanning microscopy; the results showed that the periodic structures of the crystals were maintained after immobilization.