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Abstract: We report the dielectric study of dynamical heterogeneity in miscible polymer blends composed of four kinds of polyethers, i.e., poly(butylene oxide) (PBO), poly(isopropylglycidyl ether) (PiPGE), poly(n-butylglycidyl ether) (PnBGE), and poly(t-butylglycidyl ether) (PtBGE). All polyethers exhibit both the dielectric normal mode relaxations due to fluctuation of the end-to-end vector and the segmental mode due to local motions. In blends composed of polyethers, the loss curves for the segmental modes are unimodal but are asymmetrical when the composition becomes asymmetrical, namely 75/25 and 25/75. The asymmetrical loss curve indicates that the loss curve consists of the fast and slow modes. We have resolved the loss curves into the fast- and slow modes by curve fitting assuming that the segmental modes are composed of two ε″ curves. Thus we have estimated the separation of the fast and slow modes. The separation is approximately proportional to the difference of the glass transition temperatures of the components. [Copyright &y& Elsevier]

Abstract: We report dielectric relaxation behavior in blends of sodium montmorillonite particles (MM) with a series of polymers (i.e., polyisoprene (PI), poly(propylene glycol) (PPG), and poly(butylene oxide) (PBO)). These polymers are known to exhibit the dielectric normal mode due to the fluctuation of the end-to-end vector as well as the segmental mode due to local, segmental fluctuations. The data indicate that all blend systems exhibit an additional relaxation process at a temperature region below the glass transition temperature, T g, of the pure polymer component. The intensity of the new relaxation process increases with the content of MM and hence the relaxation process can be assigned to the segmental motion of the chains intercalated in the interlayers of MM. On the other hand, the relaxation time of the normal mode reflecting the fluctuation of the end-to-end vector is the same as the neat polymers but the intensity of the relaxation process increases due to enhancement of the internal electric field by MM. [Copyright &y& Elsevier]

Abstract: We report the dielectric properties of poly(styrene oxide)s (PSO) in bulk and concentrated solution states. Since the structure of PSO is asymmetric along the backbone, the repeat unit of PSO is expected to possess the non-zero component of the dipole moment pA parallel to the chain contour as well as the perpendicular component pB. The former and latter cause the dielectric normal mode and segmental mode relaxations, respectively. Contrary to the above mentioned expectation the temperature dependence of ε″ exhibits only the primary (α) relaxation and weak secondary relaxation (β) in the glassy state. No loss peak due to the normal mode relaxation was observed in the frequency region expected from the viscoelastic terminal relaxation in bulk and toluene solutions. The dielectric behaviours of the α relaxation in the bulk state were analyzed in detail and the parameters of the Vogel–Fulcher and the Havriliak–Negami equations were determined. The Kirkwood correlation factor was determined to be 0.36. The 13C NMR spectra indicate that the present PSO samples contain about 2% head-to-head linkages. This cannot be the origin of the disappearance of the normal mode. We conclude that pA of PSO is too small to be detected. The pA calculated with molecular orbital methods supports this conclusion. [Copyright &y& Elsevier]

Abstract: We studied the relationship between segmental dynamics of matrix polymers and tracer diffusion of low mass compounds by the use of forced Rayleigh scattering and dielectric spectroscopy. Specifically poly(methyl acrylate), poly(ethyl acrylate) and poly(n-butyl acrylate) were used as the polymer matrices and six azobenzene derivatives with various substituents as the diffusant. The temperature dependence of the tracer diffusion coefficient D was measured on methylyellow (MY)/polyacrylate blends at the MY concentration of 1wt%. The results indicate that the temperature dependence of D is weaker than the dielectric loss maximum frequencies f m for the α processes of the matrices. The effect of volume of the dye molecules on D was also investigated at 305K. Comparison of the tracer diffusion coefficients among various dye/polymer systems indicates that log D in the same matrix decreases linearly with the molar volume of the dyes. [Copyright &y& Elsevier]

Abstract: We studied viscoelastic and dielectric relaxation behavior of poly(vinyl acetate)/poly(ethylene oxide) (PVAc/PEO) blends in the miscible state. Especially for the viscoelastic measurements, we used highly asymmetric molecular weight M W combinations to examine the component dynamics separately. Time–temperature superposition principle did not hold since the two components have different shift factors (a T ). We determined the a T of both components in the blends for the terminal relaxation modes. Concerning the dielectric relaxation, we observed single α-relaxation peak and found that the α-relaxation mainly reflected the segmental motion of PVAc in the blends. The dielectric and viscoelastic a T of the PVAc component showed almost the same temperature dependence compared at the same composition. From these a T data, we determined effective glass transition temperatures (T g,eff) as a function of blend composition for both components. The results were compared with the literature data for a similar miscible blend, poly(methyl methacrylate) (PMMA)/PEO [T.R. Lutz, Y. He, M.D. Ediger, H. Cao, G.Lin, A.A. Jones, Macromolecules 36 (2003) 1724]. The T g,eff’s of PEO in the two blend systems were almost the same at any compositions even though the blend partners have very different glass transition temperatures T g’s: 311K for PVAc and 405K for PMMA. If we use the Lodge–McLeish (LM) model to explain the similar T g,eff’s of PEO in both blends, the self-concentration of PEO should be dependent on the blend partner. This suggests the necessity to take into account the effect of the inter-molecular interaction in the LM model. [Copyright &y& Elsevier]

Fractionated samples of d,l-poly(lactic acid) (PLA) were prepared and the dielectric normal mode relaxation was studied for dilute and semi-dilute solutions of the PLA in a good solvent benzene. Results indicate that in the dilute regime the normal mode relaxation time is proportional to [η]Mw in agreement with the Rouse–Zimm theory, where [η] and Mw denote the intrinsic viscosity and weight average molecular weight, respectively. The dielectric relaxation strength which is proportional to the mean square end-to-end distance 〈r2〉 increases with increasing Mw with the power of 2ν, where ν is the excluded volume parameter determined from [η]. The relaxation time in the semi-dilute regime increases with increasing concentration C due to increases of the entanglement density and the friction coefficient. The relaxation time corrected to the iso-friction state agrees approximately with the dynamic scaling theories. The relaxation strength decreases with increasing concentration indicating that 〈r2〉 decreases on account of the screening of the excluded volume effect. The concentration dependence of 〈r2〉 agrees approximately with the scaling theory proposed by Daoud and Jannink. [Copyright &y& Elsevier]

Abstract: We investigated the interfacial tension γ between poly(ethylene oxide) (PEO) and polystyrene (PS) focusing our attention on the dependence of γ on the molecular weight (M) of PEO and the surfactant effect of poly(ethylene oxide-b-styrene) diblock copolymer [P(EO-b-S)]. Measurements of γ were carried out by observing electric deformation of droplets of PEO suspended in bulk PS or in a concentrated solution of PS in dioctylphthalate (DOP). The results indicate that γ between PEO and PS is almost independent of M of PEO in the high molecular weight region, but exhibits a minimum around M =500. Addition of 1wt% of P(EO-b-S) to the PEO/PS system causes a decrease of γ due to the surfactant effect of the copolymer, but γ is almost independent of further addition of the copolymer. The decrement of the interfacial tension Δγ increases with increasing molecular weight of P(EO-b-S). [Copyright &y& Elsevier]

We investigated ultrasonic attenuation, dynamic Young's modulus, Izod impact strength, and dielectric relaxation of acrylonitrile–butadiene–styrene composite polymers (ABS) in which styrene-co-butadiene rubber particles are dispersed in styrene-co-acrylonitrile random copolymer. High ultrasonic attenuation was observed around 240 K and the intensity of attenuation increased with increasing rubber content. Temperature dependence curves of dielectric loss in the frequency range from 12 Hz to 200 kHz and temperature range from 80 to 420 K exhibited four relaxation processes designated as the α, β′, β, and γ. From the relaxation map produced for the mechanical and dielectric relaxations, the ultrasonic absorption was attributed to the β and β′ processes. It was deduced that inter-grain thermoelastic process, also contribute to the ultrasonic attenuation. Correlation was found between the ultrasonic absorption and the Izod impact strength indicating that the high impact strength of ABS is partly due to the effective absorption of impact energy through those relaxation processes. [ABSTRACT FROM AUTHOR]