Effects of interfacial interactions between rubber matrix and filler surface on the structural changes of rubber matrix upon a tensile deformation of filled styrene-butadiene rubber (SBR) vulcanizates were studied by ESR and pulsed NMR. The interfacial interactions were controlled by using several kinds of surface modified silicas and carbon blacks. For silica filled systems, the degree of chain scission during tensile deformation of the samples could be evaluated from ESR results. Information on the structural changes of rubber matrix upon a tensile deformation for both carbon black filled and silica filled SBR vulcanizates could be obtained from the results of pulsed NMR. The combination of ESR and NMR results revealed that the degree of chain scission was dependent on the strength of interfacial bondings between filler and rubber molecules and the chain scissions are suggested to occur in the interfacial regions between rubber molecules and fillers.

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1,4-Cis-selective and molecular weight control of the polymer in the polymerization of butadiene (Bd) with various metallosalen [metal=Co, Ni, Fe, V, Ti; salen=N,N′-bis(salicylidene)ethylenediamine] in combination with methylaluminoxane (MAO) was investigated. The activity for the polymerization of Bd was influenced by both substituents of the salen ligands and mixing order of reagents. The activity for the polymerization of Bd with metallosalen complexes activated by MAO in the presence of Bd was higher than that in the absence of Bd. By introducing the tert-butyl group in the aromatic ring of salen, the activity for the polymerization of Bd increased, but the microstructure of the poly(Bd) did not change significantly. Among the metallosalen complexes examined, N,N′-bis(3,5-di-tert-butylsalicylidene)ethylenediaminato Co(II) (1-Co) complex in combination with MAO gave the high molecular weight polymer with highest 1,4-cis content. Molecular weight control of the polymer was achieved by the polymerization of Bd with 1-Co/MAO catalyst.

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Mesoporous silica (MPS) was used for poly(ethylene oxide) (PEO)-based solid polymer electrolytes as novel inorganic filler. For improvement in ionic conductivity in solid state, a room temperature ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate, was introduced into periodic nano-tunnels of MPS, and the modified MPS (IL-MPS) was filled with PEO-LiBF₄ electrolyte. Ionic conductivity of neat-MPS-filled composites was approximately 4-fold higher than that of the original electrolyte. On the other hand, the conductivity was more than 11-fold enhanced by addition of IL-MPS, to be more than 10⁻⁶ S/cm at 30°C and at least 10 wt% silica contents. The conductivity increased with increasing IL-MPS contents, to be a maximum value of approximately 3×10⁻⁶ S/cm at 30°C and at 40 wt%. Dynamic mechanical measurements for neat- and IL-MPS composites revealed that the addition of fillers improves storage modulus of PEO-based electrolytes at room temperature. The addition of IL-MPS was able to realize the improvement in both ionic conductivity and storage modulus.

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Poly(ethylene-co-vinylacetate) (EVA) was mixed with sodium montmorillonite (MMT) at 90/10 wt. ratio. EVA was also mixed with an organophilic montmorillonite (o-MMT) prepared by replacing Na⁺ in MMT with trimethylstearylammonium cation. The structure and mechanical properties of the composites were studied by scanning electron microscopy (SEM), transmission electron microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, and dynamic mechanical analysis. In the EVA/MMT composite, MMT particles were poorly dispersed in the order of a few µm. The composite was opaque. By contrast, in the EVA/o-MMT composite, the exfoliated silicate layers were nicely dispersed in EVA matrix. It was a transparent material. The composite showed an interesting reinforcing effect; i.e., the rubbery plateau modulus was retained even above the melting point of EVA. The rubbery modulus seems to originate from a formation of the “house-of-cards” structure of silicate layers.

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A carbon black (CB) filled styrene-butadiene rubber (SBR) compound was investigated by acoustic techniques, scanning acoustic microscopy and longitudinal wave velocitometry.
The CB agglomerates of larger than 5 µm dispersed in the compound mixed by two-roll mill were observed as black spots in acoustic micrographs. On the other hand, the CB agglomerates in the compound mixed by oil-pressure kneader were not observed in the acoustic micrograph, since the particle size of the agglomerates was less than 5 µm.
The density and the longitudinal wave velocity of the compound were measured as a function of the weight percentage of the CB. The density and the velocity increased linearly with the content of the CB. The mass ratio of the bound rubber to the CB in the unvulcanized sample was determined by using toluene extraction and thermo gravimetric analysis. The partial specific adiabatic compressibility of the CB was estimated as (−0.5±0.5)×10⁻¹⁰ Pa⁻¹ on the basis of the three states model. The adiabatic compressibility of the bound rubber was (2.2±0.5)×10⁻¹⁰ Pa⁻¹, and it is half of that of the SBR matrix.

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