Articles in 2013

In this paper, we have provided the first conclusive evidence that the Ni particle dispersed poly(methylmethacrylate) (PMMA) composites, which do not exhibit melting phenomenon, exhibit the positive temperature coefficient (PTC) effect when Ni content were 20 and 25vol.%. In particular, the composite with Ni content of 25vol.% exhibited PTC effect comparable to that of composites composed of crystalline polymer, and it demonstrated conductor/insulator transition. We assumed that these composites have few conductive paths, and so disconnection of conductive path occurred from slight volume expansion of PMMA by temperature rising.

Polydimethylsiloxane (PDMS) films were doped with 1% perfluoroether to lower the surface energy. Although the surface energy was lowered, the peel force did not decrease. It was found that peel force was linearly related to adhesive energy of films, and adhesive energy was inversely related to Young’s modulus. Films with low Young’s moduli evened out against surfaces easily and made good contact, which increased the adhesive forces, making the release hard. Comparatively, films with higher Young’s moduli had low peel force.

A series of novel photoactive high-performance polyamides bearing different functional group, such as CF₃, substituted imidazole and carbazole rings in their backbone, were prepared in direct polycondensation using ionic liquid media and triphenyl phosphate as an activating agent.

The particle scattering function (structure factor) P(q) of a two-dimensional flexible macromolecule (2D-FM), such as thin graphite oxide and graphene oxide, was calculated. The geometrical model used for shrinking the 2D-FM particle was the developable double corrugation surface (Miura folding) of a disk. This model described a three-dimensionally foldable and re-extendable shape and spontaneously exhibited self-avoiding condition inside a single particle. The obtained P(q) varied greatly according to the shape of the particle, which can change from a flat extended state to a three-dimensionally isotropic and dense shrunken state.

Isolated molecules of cyclic polymers were directly observed by atomic force microscopy. Interdiffusion of cyclic polystyrene/cyclic deuterated polystyrene bilayer films were investigated as functions of temperature and molecular weight by dynamic secondary ion mass spectroscopy.

Photopolymerization of thin layers of a 75/25 (w/w) Bis-GMA/TEGDMA mixture exposed to a 465-nm monochromatic light radiation was first investigated. The final methacrylate conversion was measured by FTIR spectroscopy for different light intensities I₀. Then, the variation of the light flux intensity φ inside thick samples of the previous mixture containing mineral nanofillers (Al₂O₃ or ZrO₂) was calculated by means of a numerical model by taking into account the light scattering induced by the fillers. The obtained results permit the determination of the conversion profiles inside the loaded material and the maximal thickness that can be photopolymerized without consequent alteration of the polymerization yield and of the mechanical properties.