Moriya Kikuchi

Chain dimensions and surface characterization of superhydrophilic polymer brushes with zwitterion side groups

Zwitterionic polymers constitute a unique class of polyelectrolytes which have not been studied systematically because of the difficulty in their controlled synthesis and precise physicochemical characterization. The salt-concentration dependence of the chain dimensions and swollen brush structures of polyzwitterions, namely poly(2-methacryloyloxyethylphosphorylcholine) (PMPC) and poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate] (PMAPS), in aqueous solutions of various ionic strengths was characterized by static light scattering, dynamic light scattering, atomic force microscopy (AFM), neutron reflectivity (NR), contact angle measurements, and macroscopic friction tests by sliding a glass ball under a load of 0.49 N. The hydrodynamic radius RH of PMPC was independent of NaCl concentration, whereas the RH of PMAPS markedly increased with the ionic strength. AFM and NR measurements also showed the independence of NaCl concentration of the swollen thickness of the PMPC brush in aqueous solution and significant changes in the swollen thickness of the PMAPS brush in aqueous NaCl solution. Both PMPC and PMAPS brushes showed oil detachment behavior in water and aqueous NaCl solutions. The PMPC brush had a significantly low friction coefficient (0.02–005) at a sliding velocity of 10−2 to 10−1 m s−1 in water even under a high normal pressure of 139 MPa.

Mesh-size control and functionalization of reorganizable chemical gels by monomer insertion into their cross-linking points

Mesh-size control of network structures of chemical gels, i.e. mesh expansion by insertion of styrene derivatives and mesh shrinking by insertion of divinylbenzene in the gels, was carried out. Chemical gels with alkoxyamine at their cross-linking points were synthesized by radical copolymerization of methyl methacrylate and divinyl monomer with alkoxyamine units. The monomers were inserted by heating the gels with each monomer separately, and the network size was evaluated by small-angle X-ray scattering (SAXS) measurements. Since a living polymerization procedure was adopted for the reactions, network mesh sizes were controlled precisely by controlling the reaction time and selecting an appropriate monomer. In addition, gel properties such as swelling degree and phase separation could also be controlled by employing functional monomers such as hydrophilic and fluorinated monomers. These reorganizable chemical gels combine the advantages of high stability of chemical gels with ease of structural changeability of physical gels.

X-ray photon correlation spectroscopy using a fast pixel array detector with a grid mask resolution enhancer

The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy experiments.

Preparation of styryl-ended rod-like poly(n-hexyl isocyanate) macromonomers and their radical co-polymerization behavior with styrene

Styryl-ended rod-like macromonomers consisting of poly(n-hexyl isocyanate) (2) (VB-HIC-n, where n is a degree of polymerization varying from 9 to 75) with relatively narrow molecular weight distribution (M w/M n < 1.2) have successfully been prepared in CH2Cl2 at room temperature by living coordination polymerization of n-hexyl isocyanate (HIC) using 4-vinylbenzyloxy-dichloro(cyclopentadienyl)titanium(IV) (1) as an initiator. The radical co-polymerization behavior of the rod-like macromonomers with styrene has been studied and summarized as a function of degree of polymerization of HIC. The apparent co-polymerizabilities of the rod-like macromonomer seem to be almost equivalent to styrene, suggesting that the reactivity is mainly determined by the chemical reactivity of the ended double bond.

Chain dimensions in free and immobilized brush states of polysulfobetaine in aqueous solution at various salt concentrations

The chain dimensions of free and immobilized polysulfobetaine in aqueous solution at various salt concentrations were investigated by size-exclusion chromatography with multiangle light scattering and neutron reflectivity measurement, respectively. The dependence of the z-average mean square radius of gyration ( z1/2) on the weight-average molecular weight (Mw) of free poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfo-nate) (MAPS) in aqueous solution at salt concentrations of 74, 100, 200, and 500 mM was described by the perturbed wormlike chain model using the chain stiffness parameter λ−1 the molar mass per unit contour length ML, and the excluded volume effect B. B increased from 0 to 1.8 nm with increasing salt concentration to 500 mM due to the screening of attractive electrostatic interaction between ammonium cations and sulfonyl anions by salt ions. The swollen structure of the poly(MAPS) brush in D2O changed from a shrunken state to a relatively extended state with increasing salt concentration from 0 to 500 mM NaCl/D2O solution. The thickness of the swollen poly(MAPS) brush in 500 mM NaCl/D2O was 9.0 times greater than 2 z1/2 of free poly(MAPS) due to high osmotic pressure generated by the excluded volume effect of densely grafted polymer chains.

Influence of salt concentration on swelling states of poly(sulfobetaine) brush at aqueous solution interface

Swelling states of poly(3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate) (DMAPS) brush in aqueous solutions with different salt concentrations were investigated by atomic force microscopy (AFM) and neutron reflectivity measurement. The thickness of swollen poly(DMAPS) brush evaluated by AFM was increased from 212 nm up to 352 nm with an increase in salt concentration from 0 to 0.5 M. Poly(DMAPS) brush chains formed shrunk structure in a pure water due to the attractive electrostatic inter- and intra-chain interaction of sulfobetaine groups, while the brush chains in NaCl aqueous solution were stretched up because the hydrated salt ions screened the attractive interaction.

Characterization of Surface Microstructures on Bio-based Polymer Film Fabricated with Nano-imprint Lithography by Synchrotron Radiation Small Angle X-ray Scattering

Nano-imprint lithography (NIL) is a simple, low cost and high-resolution patterning method. However the precise evaluation method of nano-imprinted structure has not been established. Synchrotron radiation small angle X-ray scattering (SR-SAXS) measurement is a nondestructive and high resolution characterization method. In this study, we attempt to fabricate nanostructures on the poly(lactic acid) (PLA) film by NIL and evaluated with microscopic and scattering techniques. The mold with line/space pattern was used for NIL. Scanning electron microscope observation confirmed the formation of surface nano-structure in large areas. Also, nano-imprinted PLA film was evaluated using SR-SAXS measurement. The scattering patterns obtained from nano-imprinted PLA films were clearly observed up to higher order scattering spots. These results suggested that highly regular structure was fabricated on the surface of PLA films.

X-ray Photon Correlation Spectroscopy of Silica Particles Grafted with Polymer Brush in Polystyrene Matrix

X-ray photon correlation spectroscopy system was setup at SPring-8, BL19LXU, and the partial coherence scattering data from the silica particles grafted with polymer brush in polystyrene matrix were measured. Firstly, the static speckle patterns were checked. Below the glass transition temperature of polystyrene (Tg), speckles were clearly observed, on the other hand, above Tg, the scattering patterns became smooth and speckles were hardly observed. These variances of the speckle patterns result from the particle motion. Secondly, from the time variance of the speckle data, time autocorrelation functions g2(q,t) are calculated. While the flat behaviour of g2(q,t) without relaxation were observed below Tg, the relaxation behavior with relaxation time~100–101 were observed above Tg

Static and Dynamic Scattering from Polysulfobetaine Immobilized on Silica Nanoparticle in Ionic Liquid

Monodisperse silica nanoparticles were immobilized with poly[3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate)] (SiNP-PMAPS) by surface-initiated atom transfer radical polymerization. SiNP-PMAPS was characterized in 1-hexyl-3-methylimidazolium chloride (HMImCl) solution by dynamic light scattering (DLS) and synchrotron small angle X-ray scattering (SAXS) measurements. The relaxation spectrum of DLS and SAXS profile for SiNP-PMAPS solutions showed a unimodal distribution attributed to the homogeneous dispersion of SiNP-PMAPS in the HMImCl without any aggregations. The scattering factor from the SiNP-PMAPS in HMImCl was described by the core-shell model considering interacting excluded-volume chains and assuming Schulz distributed core with the thickness of polymer layer of 56 nm.

Chain dimension of polystyrene-like hyperbranched polymers with various chain end groups in THF

A hyperbranched polymer (HPS-DC) synthesized using N,N-diethylamino -dithiocarbamoylstyrene as an inimer and a hyperbranched poly(4-methylstyrene) (HPS-H) prepared by hydrogenation of the HPS-DC are characterized in tetrahydrofuran (THF) solutions by static and dynamic light scattering measurements. The experimental values of z-averaged mean-square radius of gyration ( z1/2) and hydrodynamic radius (RH) of the HPS-H have smaller dimensions than those of the linear polystyrene (PS) at the same degree of polymerization (Nw), whereas the RH of the HPS-DC in the region of Nw z1/2 and RH for the HPS-H are described by a randomly trifunctional branched polymer model with the molecular weight per a branch point (4.55 × 103 g/mol) and the chain dimensions of the linear PS in THF at 25 °C.