Articles in 2012

Our group has developed a novel method to produce nanocellular and nanoporous structures using block copolymer as template and supercritical carbon dioxide. To characterize nanocells and nanopores, small angle X-ray scattering (SAXS) has an important role. In particular, grazing incident SAXS reveals embedded nanocellular and nanoporous structures in thin films. Additionally, SAXS can be used for in situ measurement to follow the process of nanocellular and nanoporous formation in supercritical carbon dioxide. Our recent progresses of fabrication and SAXS characterization of nanocellular and nanoporous structures will be reviewed.

Composite polyether electrolytes filled with oriented MMT layers in perpendicular (M_⊥) or parallel (M_//) to the film surface were successfully obtained by the application of strong magnetic field. The ionic conductivity of the M_⊥ composite with 5 wt% of Li-MMT was 1.2 × 10⁻⁵ S cm⁻¹ at 30 °C, and the value was more than six times greater than that of the original electrolyte (PMEO₁₀LiClO₄). We concluded that the ionic migration on the layer of oriented MMT has a crucial role to increase the conductivity with lower activation energy.

The effects of thermal gradient on dynamical behavior of nanoparticles dispersed in polymer matrix were studied by X-ray photon correlation spectroscopy. Anisotropic motions of nanoparticles were observed when the sample was kept in a cell using a capillary tube covered with copper block. As the same experiment using another cell without such thermal gradient clearly demonstrated that even the small thermal gradient around the probe windows caused the anisotropic dynamical behavior.

We studied the formation mechanism of ‘nano-oriented crystals (NOCs)’ of isotactic polypropylene in elongational crystallization through crystallization temperature dependence of NOCs formation. We proposed a ‘chain reaction model’ of NOCs formation: The local oriented melt is formed by the melt elongation, which significantly accelerates nucleation; and, generated nuclei accelerate formation of local oriented melt that accelerates nucleation again. We obtained the nucleation rate (I_obs) of NOCs against the degree of supercooling (ΔT). Here, an equilibrium melting temperature in the oriented melt T_m⁰=220 ^°C is estimated from observation of NOCs formation. I_obs was well fitted by well-known equation of for homogeneous nucleation in classical nucleation theory, where C is a constant. Therefore, we concluded that NOCs formation is mainly controlled by the homogeneous nucleation process.

Simultaneous small- and wide-angle X-ray scattering studies on crystallization dynamics of poly(4-methylpentene-1) (P4MP1) from melt by Kazuki Mita, Hiroshi Okumura, Kazuki Kimura, Takeharu Isaki, Mikihito Takenaka and Toshiji Kanaya. Crystallization process of P4MP1 under an isothermal condition was investigated by means of simultaneous small- and wide-angle synchrotron radiation X-ray scattering. The changes in lamella structure and crystal lattice during the crystallization were elucidated for the first time: the lamellae thickness is kept constant, whereas the lattice constant a changes toward the most stable value. We also found that there is some inhomogeneous structure even in the melt and in the induction period and the subsequent crystallization consists of the first and the second processes.

Ab initio statistical mechanics based on the rotational isomeric state scheme and molecular orbital calculations has been applied to poly((R)-3-hydroxybutyrate)(PHB) to elucidate its conformational characteristics and configurational properties. This article presents fully consistent interpretations on its bond conformations, solution properties, crystal structure, thermal properties and interactions with a PHB depolymerase in terms of the conformational characteristics.

Rubber-filler systems have been widely used in industry. Fillers are not dispersed homogeneously and often form hierarchical structures in rubber matrices over a wide range of length scale from nanometer to micron meters, such as primary particles, aggregates and agglomerates. The combined scattering methods are powerful tools to characterize the structures quantitatively.

We carried out isothermal crystallization experiment for isotactic polypropylene (iPP) containing 1,3:2,4-bis(p-methylbenzylidene)sorbitol (PDTS) as a nucleation additive. Avrami analysis for iPP/PDTS systems showed that the Avrami exponent decreased from 3.5–4 to 2 with decrease of the crystallization temperature T_c only by 4 °C, being contrasted with iPP, where the exponent was 4 for all T_c. This study shows that the iPP/PDTS crystallization kinetics and its temperature sensitiveness were determined by the competition between two events: PDTS network growth and iPP crystallization.

When O-(4-acyloxyanilinocarbonylmethyl)-4-tert-butylcalix[8]arene films were irradiated for 60 min with 254-nm UV light from a low-pressure mercury lamp, the calixarene derivative 1 underwent a highly selective photo-Fries rearrangement in the film state to yield the corresponding Fries-rearranged product 2 along with a minor amount of the fragmentation product 3. This photochemical rearrangement enhanced the refractive index of the films by as much as 0.015.

Hyperbranched poly(ether ether ketone)s with hydroxyl terminal groups were prepared by a one-step synthesis of an AB₂-type monomer 3,5-dihydroxy-4′-(4-fluorobenzoyl)diphenylether through an aromatic nucleophilic substitution reaction. The degree of branching determined by ¹H-NMR analysis was about 52%. The reduced viscosities of the hyperbranched polymers were higher than those of the corresponding dendrimers, the glass transition temperatures of the hyperbranched polymers were higher than those of the dendrimers and the existence of entanglement among the hyperbranched polymer molecules was suggested.

The new experimental system has been launched by coupling with the measurement techniques, which are grazing incidence small/wide-angle X-ray Scattering (GISWAXS) and grazing incidence X-ray diffraction (GIXD), as well as X-ray reflectivity (XR), at the BL03XU of SPring-8. Using this integrated system, we can achieve to measure the hierarchical structure of the same sample.

We visualized strain field of polymer matrix using an FEM simulation based on the knowledge of 3D structural configuration of silica particles in rubber. The configuration was obtained by using the Zernike-type phase contrast x-ray imaging method.

The phase-transition point Tc from the low- to high-temperature phase of ethylene-tetrafluoroethylene copolymer is dependent on the type of the third monomeric unit having long (C4F9) or short (CF3) side groups. The existence of side chains affects more or less the unit cell dimension as well as the higher-order structure of stacked lamellae.

A method is described that can predict the miscibility of the great majority of polyolefins based just on their chemical architecture. The miscibility of polyolefins is shown to be essentially controlled by their solubility parameters, d, which in turn depend on the chain dimensions of the chains through the packing length l_p. A method to estimate l_p from chain architecture is also shown, giving a very powerful mechanism to predict the mixing thermodynamics from chemical structure.

The Δs′ value (s′_max−s′_min) represents the cross-linking efficiency of peroxide, which is defined as the number of moles of chemical cross-links formed per mole of peroxide. Efficiency of peroxide is higher for EOCs with lower-octene content. The reason might be difficulty of peroxide-free radicals to attack the main chains due to increased hindrance by octene side groups.

Radical copolymerization of alkyl 2-norbornene-2-carboxylates 1a–c with alkyl (meth)acrylates to afford copolymers bearing norbornane framework in the main chain is described. γ-Butyrolactone- and hydroxy group-containing norbornene-based monomers 1b and 1c were newly synthesized and their radical copolymerization behavior with n-butyl acrylate was examined. Methyl 2-norbornene-2-carboxylate 1a and the new monomers 1b and 1c were employed as a comonomer for radical terpolymerization with lactone- and adamantane-containing (meth)acrylates to afford copolymers, which could be utilized as new chemically amplified 193-nm photoresist materials.

Grazing incidence small-angle neutron scattering (GISANS) allows for the investigation of nanostructures in thin films and at surfaces due to the use of a reflection geometry. Possibilities and challenges of GISANS are reviewed with several different examples of thin nanostructured polymer films. With GISANS buried lateral structures can be probed destruction free using the variable-probed depth as function of the incidence angle. By this, averaged statistical information is detected over the large illuminated sample surface.

This review describes the developments of self-assembled photonic crystals (PCs) of chiral liquid crystals (CLCs) and colloidal crystals (CCs) for laser applications. Both CLCs and CCs have intrinsic capabilities to spontaneously assemble 1D-PCs and 3D-PCs, respectively. By combining fluorescence dyes in the structures, the stimulated laser action can be generated by optical excitation. Moreover, the optically excited lasing is controllable by external stimuli due to their self-organization. This review highlights the research backgrounds of CLCs and CCs, as well as the experimental results of soft and tunable laser applications.

We present the optimization of poly(N-vinylcarbazole) (PVCz)-based photorefractive composite films for use in a dynamic holographic imaging system. The compositions of the composite films used in this study included PVCz/4-azacycloheptylbenzylidenemalononitrile (7-DCST)/carbazoylethylpropionate (CzEPA), N-ethylcarbazole (ECz), benzyl n-butyl phthalate (BBP)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), or 2,4,7-trinitro-9-fluorenone (TNF) (44/35/20/1 wt%). PVCz with molecular weights of 23 000, 100 000, 290 000, 370 000, and 810 000 gmol⁻¹ were used. The PPC film (PVCz with Mw: 370000/7-DCST/CzEPA/TNF, 44/35/20/1 wt%) was observed to be the most well-balanced for photorefractive performance. To demonstrate the practical application of these films, dynamic holographic images were reflected from a spatial light modulator (SLM). The optimized PPC film was used in the dynamic holographic imaging system, and well-balanced dynamic holographic images were obtained.

The cloud point was determined for aqueous solutions of two poly(N-isopropylacrylamide) samples, one having a hydrophobic nonionic chain-end group (M sample) and the other having a hydrophilic anionic chain-end group (R sample), with an addition of two kinds of surfactants, anionic sodium n-dodecyl sulfate (SDS) or cationic n-dodecyltrimethylammonium chloride (DTAC). It is found that behavior of the cloud point as a function of the concentration c_s of the surfactants largely depends on the kinds of chain-end group and surfactant.