Shinzo Kohjiya

High ionic conductivity of new polymer electrolytes based on high molecular weight polyether comb polymers

High molecular weight polyether comb polymers, poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] P(EO/MEEGE), have been used as matrixes of polymer electrolytes. The high molecular weight (>10 6 ) polymers give self-standing and elastic polymer electrolyte films without chemically cross-linked structures at room temperature, when complexed with electrolyte salts. With increasing the composition of MEEGE in the copolymers, the degree of crystallinity of the polymer electrolytes decreases, and the ionic conductivity appreciably increases. The increase in the conductivity cannot be explained only by the crystallinity decrease, the increase in the number of highly mobile ether side chains with the increase in MEEGE composition contributes to achieving the high conductivity. The fast ion transport would be realized in cooperation with the fast side chain motion. The polymer electrolytes complexed with lithium his(trifluoromethylsulfonyl)imide (LiTFSI) exhibit higher conductivity than those complexed with a conventional salt, lithium perchlorate. The polymer electrolytes, P(EO/MEEGE) containing 9 mol% of MEEGE complexed with LiTFSI, exhibit high ionic conductivities of 10 -4 S cm -1 at 30°C and 10 -3 S cm -1 at 80°C. An electrochemically stable potential window, established by solid state cyclic voltammetry using microelectrodes, is at least 4V from the Li/Li + potential.

The Effect of Bis(3-Triethoxysilylpropyl) Tetrasulfide on Silica Reinforcement of Styrene-Butadiene Rubber

Abstract Bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) was found to affect the curing characteristics and the physical properties of styrene-butadiene (SBR) gum rubber and xin situ silica-filled SBR vulcanizates. Silica incorporated by the in situ sol-gel reaction of tetraethoxysilane with TESPT showed a much higher reinforcing efficiency than did conventional mechanical mixing and the in situ method without TESPT. The higher reinforcing efficiency is attributed to the formation of a silica-rubber network, which also changed the dynamic mechanical behavior of the SBR vulcanizates. Transmission electron microscopy observations showed in situ silica incorporation of very fine particles in comparison to the sol-gel process without TESPT.

Reinforcement of General-Purpose Grade Rubbers by Silica Generated In Situ

Abstract The use of the sol—gel process on general-purpose grade rubbers is reviewed in the absence or presence of silane coupling agents. The sol—gel reactions of tetraethoxysilane (TEOS) in epoxidized natural rubber (ENR), styrene—butadiene rubber (SBR) or butadiene rubber (BR) vulcanizates produced silica generated in situ. This silica was found to be a good reinforcing agent by investigating tensile and dynamic mechanical properties and morphology observation by transmission electron microscopy (TEM). The amount of silica formed was limited by the degree of swelling of the rubber vulcanizate by TEOS which was the precursor of the silica. However, the dispersion of silica generated in situ was better than conventionally added silica due to its formation in place. Also, it was noted that the diameter distribution of in situ silica was monodispersed. Silane coupling agents, such as mercaptosilane, aminosilane, and bis(3-triethoxysilylpropyl) tetrasulfide, were compounded in the vulcanizates and their eff...

Structural development of natural rubber during uniaxial stretching by in situ wide angle X-ray diffraction using a synchrotron radiation

Structural development of natural rubber during uniaxial stretching was examined by an in situ wide angle X-ray diffraction measurement using a synchrotron. During stretching, the amorphous part showed little change, i.e. an amorphous halo remained clear even at 500% strain. The fraction of induced crystals was very small, though a clear crystalline pattern was observed at 400% strain. Some polymer chains were oriented and crystallized, but most of the chains were not oriented at all in spite of large deformations of the specimen. Only a small amount of polymer chains contributes to the stress and hysteresis loss during elongation.

In situ formed silica particles in rubber vulcanizate by the sol-gel method

In situ silica filling of butadiene rubber (BR) was carried out by the sol-gel process using tetraethoxysilane (TEOS). BR was sulfur-cured, and the resultant crosslinked BR was subjected to soaking in TEOS at 30°C for 48 h. The swollen vulcanizates were kept in the aqueous solution of n-butylamine at 30°C for 24 h, followed by standing at 50°C for 72h to conduct the in situ sol-gel reaction of TEOS. The resultant vulcanizates contained silica particles which were prepared by the in situ filling technique. They were subjected to tensile and dynamic mechanical measurements, differential scanning calorimetry and transmission electron microscopic observation. The in situ formed silica was dispersed homogeneously in the rubbery matrix. The size of in situ silica was influenced by the crosslinking density, probably because it was formed in the crosslinked rubber networks. Compared to the conventional silica-filled BR vulcanizate, which was prepared by mechanical mixing of the silica particles, the new vulcanizates with the in situ formed silica showed better mechanical properties.

Characterization of comb-shaped high molecular weight poly(oxyethylene) with tri(oxyethylene) side chains for a polymer solid electrolyte

Structure and properties of high molecular weight comb-shaped poly(oxyethylene)s with tri(oxyethylene) segments as side chains (TECs) were evaluated as a polymer solid electrolyte. The weight-average molecular weights of the TECs were in the order of 10 6 , and the contents of the side chain were 5, 11 and 18 mol%. The presence of tri(oxyethylene) side chains decreased the crystallinity of oxyethylene segments, i.e., TECs with higher side chain content showed lower crystallinity. The crystallite size of oxyethylene units in TEC films did not change, but the amorphous phase content became higher by the introduction of tri(oxyethylene) side chains. The crystalline structure in TECs was found to be Form I monoclinic system and a 7:2 helical structure. When LiClO4 was doped in the TECs at the concentration of [Li]:[O]0.05, TECs with 11 and 18 mol% tri(oxyethylene) segments showed the ionic conductivities in the order of 10 4 Sc m 1 at 30°C and 10 3 Sc m 1 at 80°C, respectively, which were a class of the highest ionic conductivity reported. TECs doped with the salt formed very elastic self-standing film without crosslinking. Salt-doping at the concentration of [Li]:[O] 0.05 decreased the crystallinity of polymers, but the crystallite sizes were almost equal with those of the non-doped films.

A study on the structural changes during uniaxial drawing and/or heating of poly(ethylene naphthalene-2,6-dicarboxylate) films

The structural changes in the uniaxial drawing process of an unoriented amorphous film of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) and in the heating process of an oriented amorphous film of PEN were studied using X-ray diffraction apparatus equipped with imaging plates. This apparatus allows us to record a time-resolved series of two-dimensional patterns of wide-angle X-ray diffraction in rapid succession, and, therefore, we can follow the structural changes during uniaxial deformation and/or thermal treatment processes. The results are as follows: (1) When an unoriented amorphous PEN film was stretched below Tg (= 117 °C), it could be elongated up to a draw ratio (DR) of 4–5 via neck formation and became an oriented amorphous film. (2) In the heating process of the oriented amorphous film (DR = 3.6, 65 °C), crystalline reflections started to appear near 120 °C, accompanied by streaks on the off-equatorial layer lines. The existence of these streaks on such layer lines indicates a lattice distortion due to the axial shift of neighbouring chains along the chain axis with respect to one another. Finally the film exhibited a fibre structure (transverse isotropy). (3) When an unoriented amorphous PEN film was drawn at 150 °C, the film exhibited a fibre structure accompanied by a lattice distortion that is similar to that mentioned above, and thereafter frequently showed so-called double orientation (uniplanar axial orientation: (10)[001]) in which naphthalene rings in the main chain are preferentially aligned parallel to the film surface despite the fact that the film was deformed in the mode of uniaxial free-width drawing.

In situ filling of silica onto "green" natural rubber by the sol-gel process

Abstract The sol—gel reaction of tetraethoxysilane produced the fine and well-dispersed in situ silica particles in the “green” natural rubber (NR) matrix before curing. This new method was developed for a NR/silica composite material, and a good reinforcement effect of in situ silica was observed on the NR vulcanizate. The method is expected to be an industrially practical technique. The in situ silica did not much inhibit the accelerated sulfur curing. Thus, it is estimated that the concentration of silanol groups on the in situ silica surface was smaller than those on the conventional silica surface. The silica—silica interaction of in situ silica seems to be weaker to result in better dispersion in the rubber matrix compared with the conventional silica. Atomic force microscopy suggested that the wettability of NR onto in situ silica was higher than that onto conventional silica. The hardness, modulus at 50% elongation and the storage modulus at room temperature of in situ silica-filled NR vulcanizate...

Effect of silane-coupling agent on natural rubber filled with silica generated in situ

The effect of silane coupling agent was investigated for the novel in situ silica loading to the natural rubber (NR) matrix. The silica was generated in situ by the sol-gel reaction of tetraethoxysilane in the NR matrix before its crosslinking. γ-mercaptopropyltrimethoxysilane (γ-MPS) significantly prevented the delay of sulfur curing and increased the wettability of NR onto in situ silica, which resulted in the increase of reinforcement effect for the NR vulcanizate. γ-MPS decreased the interaction between the in situ silica particles followed by dispersing the in situ silica particles homogeneously and decreasing the hardness, compression set, hysteresis loss and storage modulus at the rubbery state of in situ silica-filled NR vulcanizate. The NR/in situ silica composite with γ-MPS is a promising material for a high performance rubber product.

Reinforcement of styrene–butadiene rubber vulcanizatebyin situsilica prepared by the sol–gel reaction oftetraethoxysilane

In situ silica reinforcement of styrene–butadiene rubber (SBR) has been achieved by a sol–gel process using tetraethoxysilane (TEOS). SBR was sulfur-cured and the sol–gel reaction of TEOS was carried out in TEOS or in a TEOS–tetrahydrofuran (THF) mixture. The in situ silica was filled homogeneously in the rubber matrix and the size of the in situ silica was influenced by the cross-linking density of the SBR vulcanizate. n-Butylamine was effective for the method using TEOS only, whereas both hydrochloric acid and n-butylamine worked as catalysts under the experimental conditions using THF for the in situ polymerization of TEOS in the SBR vulcanizate. From the viewpoint of the reinforcement of in situ silica and the size stability of the SBR vulcanizate, the method using only TEOS was found to be better than the mixture system. This conclusion was based on the results of tensile tests, dynamic mechanical measurements, optical and transmission electron microscopies.