Research articles

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.

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.

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.

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.

To investigate the electroactive shape-memory property of the hydro-epoxy composites, a sample with 1.9 wt% carbon black powder is investigated. The figure shows that the recovery of the original shape occurred after only a few minutes. Moreover, the shape recovery ratio (Rr) of the electroactive shape-memory hydro-epoxy composite is almost 100%. This finding indicates good electroactive shape-memory performance.

Curing studies and reaction mechanism of MF resin was studied by thermal and spectroscopic tools comparing DSC and FTIR studies explains the two-stage thermal curing mechanism. The first step of thermal curing at temperature range of 140–160 °C is the reverse reaction of methylol groups to melamine and second step occurring at temperature >160 °C is the crosslinking of methylol groups to the final product, methylene bridge. Hence, by the mutual agreement of DSC and FTIR studies, a possible reaction route was derived for the thermal curing process. The DSC–TGA thermogram supports the two-step process of the cure reaction by exhibiting two peaks in the same temperature region.

A highly bulky methacrylate, tris(trimethylsilyl)silyl or supersilyl methacrylate, was polymerized quantitatively with 9-fluorenyllithium in the presence of (−)-sparteine as a chiral ligand in toluene at −78 °C to give insoluble polymers. The obtained polymers exhibited high isotacticity (mm>99%) and chirality, which was confirmed by diffuse reflectance circular dichroism spectroscopy. Thus, the bulky silyl methacrylate undergoes asymmetric anionic polymerization with the chiral initiating systems via formation of a prevailing one-handed helical conformation.

The possibility of phase separation of benzoxazine (BZ)/epoxy resin (ER) blends were investigated via model components. The experiment result indicated that if the molecular weight of ER can increase to a higher extent (for example, ⩾4370 g mol⁻¹) before the polymerization of BZ resin occurs, phase separation of BZ/ER blends can take place in-situ. By varying the ER content in the system, sea-island structure, ribbon weave-like bi- continuous structure and inverted-phase structure can be obtained.

Poly(ɛ-caprolactone)₂-b-poly(L-lactide)₂ miktoarm block copolymers were successfully synthesized via ring-opening polymerization with protection–deprotection procedure, using pentaerythritol as initiator. The degradation behavior of (PCL)₂-b-(PLLA)₂ microspheres, which were produced by oil-in-water emulsion solvent extraction/evaporation method, showed that the degradation occurred from the surface to the interior as a combined degradation model with surface erosion and bulk degradation.

Assembly of poly(acrylic acid) (PAAc) gel particles with DNA–ethidium bromide (EtBr) complexes was synthesized and the pH-sensitivity was evaluated for application in optical-sensor devices. The swelling ratio of the assembly was regularly changed with pH and the response speed of the assembly was approximately the same as the gel particles. The great increase in pH-sensitivity of the assembly was assumed to be induced by the porous structure. The fluorescence intensity was changed corresponding to the volume alteration of the assembly. The assembly could quickly detect the pH in the surrounding as an optical-signal.