Shoji Suehiro

Ordered structure and critical phenomena of a semidilute solution of polymer mixtures under shear flow

A semidilute solution of a polymer mixture with a nearly critical composition was studied by using the small‐angle light scattering method as a model system to study ordered structures and critical phenomena of mixtures under shear flow. The experimental studies revealed that there are five regimes in the shear‐rate dependence of the concentration fluctuations of the solution, as discussed in the text, including the regime in which the ‘‘shear‐induced homogenization’’ takes place. The results were interpreted, as much as possible, with the theories developed for binary mixtures of simple liquids and, when necessary, with a theory proposed here for polymer systems. Unique features of polymer dynamics in comparison with the dynamics for the critical mixtures of simple liquids were presented in the text, e.g., the shear‐rate (S) dependence of the cutoff wave number being proposed to be given by qc,S∼(Dcξ20)−1/4 S1/4 rather than qc,S∼(6πη/kBT)1/3S1/3 for the simple liquids.

The 6 m Point-Focusing Small-Angle X-ray Scattering Camera at the High-Intensity X-ray Laboratory of Kyoto University

A new multipurpose X-ray small-angle scattering camera system consisting of a rotating-anode X-ray generator, a double-focusing collimator and a two-dimensional position-sensitive detector has been developed at the High-Intensity X-ray Laboratory of Kyoto University. The overall camera length is 6 m, and the sample-to-detector distance can be varied in 0.5 m increments up to 3 m to cover scattering angles ranging from 0.001 to 0.18 rad. The collimator consists of a pair of crossed-plane total-reflection mirrors of 40 cm in length. The mirrors, which are mechanically bent to form cylindrical surfaces, provide point collimation free of collimation error. General-purpose sample holders equipped with a programmable temperature controller are provided for both transmission and scattering measurements; the temperature is maintained within ± 0.1 K in the range of 223–573 K. A cryostat for measurements down to 20 K, a dynamic sample deformation apparatus, and a temperature-jump equipment are also available. The multi-wire delay-line position-sensitive proportional counter has an active area of 128 × 128 mm with a spatial resolution of 0.5 × 1.0 mm. The data acquisition is controlled by a real-time front-end processor through a CAMAC interface. The data are recorded in a dual-port histogramming memory of 32 bit × 1 Mwords, which enables direct access to the data from the main computer for real-time monitoring and analysis. The performance of the camera is demonstrated with some selected examples: diffraction patterns from carp lateral line nerve myelin and chicken-tendon collagen fibrils, a Guinier plot of the scattering from polystyrene in dilute solution, and time-resolved measurements of polypropylene during the annealing process.

Time-resolved detection of x-ray scattering for studies of relaxation phenomena

Abstract An instrument for time-resolved detection of small-angle and wide-angle x-ray scattering is described. The apparatus consists of a 12-kW rotating-anode x-ray generator, a linear position-sensitive detector, a two-parameter multichannel analyzer to record the time-dependence of x-ray scattering patterns, a servo-controlled hydraulic sample deformation device, a temperature-controlled environmental chamber, a programmable function generator, a programmable timer and a microcomputer. The programmable function generator is used to control the mechanical or thermal stimulus on the sample under variable conditions and to synchronize the x-ray data acquisition with the stimulus. The environmental chamber allows temperature control of the sample between −100 and 300°C. Two experimental methods, involving transient and oscillatory experiments, for time-resolved studies with this apparatus are discussed. Experimental studies on kinetics of oriented crystallization of cross-linked polybutadiene and on lamellar deformation of tubular-extruded poly(1-butene) films are presented as typical applications of time-resolved x-ray scattering technique.

Quasielastic light scattering studies of swollen and stretched polymer gels

Cooperative diffusion D of polyacrylamide gels in water was investigated by quasielastic light scattering both under the isotropically swollen state and under the uniaxially stretched and swollen state. The concentration (Ce) dependence of D for the isotropic gels having equilibrium degrees of swelling was measured by systematically changing crosslinking density of gels. The results yielded D=(3.4±0.5)×10−6 C0.76±0.03e cm2/s, in accord with a scaling prediction. For each of the gels prepared and having a given Ce, the uniaxial stretching was applied, and the values D were investigated as a function of extension ratio α and direction β with respect to the stretching direction. The results gave D (α,Ce)=(3.4±0.5)×10−6 αx Cye cm2/s, where x=2/3 for β=0° and −1/4 for β=90°, and y=0.76, independent of α and β. The results clearly indicate that upon increasing α, D increases and decreases, respectively, in the direction parallel and perpendicular to the stretching direction, implying suppression and enhancement...

Fractal dimension analysis of polyacenic semiconductive (PAS) materials

Abstract The fractal dimensions D of the pristine and the Li-doped polyacenic semiconductive (PAS) materials have been analyzed by small-angle X-ray scattering (SAXS) and compared with that of graphite. It has become clear that the Li doping generally makes D smaller, which suggests fixation effect of the nanopores on the surface of the material by the doped Li atoms. It is pointed out that the fractal dimension analysis affords an alternative picture to the conventional N 2 adsorption and rather new technique using 129 Xe nuclear magnetic resonance method in discussion of the surface structures for general amorphous carbon particularly when it is doped or mixed with binders.

Fractal properties of polymer crystals

Small angle x‐ray scattering is performed on the crystals of polyethylene and polytetrafluoroethylene up to Porod’s region. The scattering intensity I obeys a power law for the magnitude of the scattering vector q for large values of q: I∼q−α. The exponent α is smaller than 4 given by Porod’s law. If it is assumed that the folded chain crystals and the extended chain crystals have the fractal surface, the fractal dimension is from 2.2 to 2.8 depending on the crystallizing condition.

Rheo-optical studies on the deformation mechanism of semi-crystalline polymers. IX. Dynamic birefringence behaviour of a high-density polyethylene film having row nucleated crystalline texture of c-axis orientation☆

Abstract The dynamic birefringence behaviour of a high-density polyethylene film having a row-nucleated crystalline texture of cylindrites oriented along the machine direction of fabrication was investigated over frequency and temperature ranges covering the α mechanical dispersion of this material. The results are discussed in combination with the dynamic X-ray diffraction behaviour of the material so as to explore the structural origins of the α mechanical dispersion, not only for this particular material, but also for bulk-crystallized polyethylene having a spherulitic texture. Two deformation processes contribute to the α 1 mechanism, corresponding to the lower temperature relaxation process in the α mechanical dispersion; i.e. (i) a lamellar detwisting process involving the rotation of crystal grains within the crystal lamellae or of lamellar segments around the crystal b -axis or the lamellar axis, which predominates in the MD (machine direction) specimen, and (ii) lamellar shearing associated with the rotation of the crystal grains or the lamellar segments around the crystal a -axis, which is accentuated in the TD (transverse direction to fabrication) specimen. An additional deformation process, lamellar bending, is also observed in the MD specimen as being likely elastic in the dynamic response, and its contribution is found to be substantial, not to the α dispersion, but rather to the β dispersion of this material. The α 2 mechanism corresponding to the higher temperature relaxation process in the α mechanical dispersion is observed to be more pronounced in the TD than in the MD specimen. The apparent dynamic crystal lattice compliance shows a definite dispersion during activation of the α 2 mechanism, but a slight dispersion during activation the α 1 mechanism, suggesting that the α 2 mechanism must be related to an intracrystal relaxation process whereas the α 1 mechanism must be associated with an intercrystal relaxation process at their boundaries.

Static and dynamic deformation mechanisms of a high-density polyethylene having rownucleated crystalline texture of a-axis orientation as observed by orientation distribution function of crystallites

Abstract The rheo-optical properties of a high-density polyethylene having a row-nucleated crystalline texture of a -axis orientation were investigated in the machine direction (MD) and transverse direction (TD) of fabricating the specimen. The tensile complex dynamic compliance function J∗ displays two dispersions designated as the α 2 and α 2 mechanical retardation processes with activation energies of about 21 and 35 kcal mol −1 , respectively, for both MD and TD specimens, and the complex dynamic stress-optical coefficient function M∗ exhibits a single discrete dispersion designated as the α optical retardation process with an activation energy of about 24 kcal mol −1 for both specimens over the same frequency and temperature ranges as those covered for the dynamic mechanical measurements. The real and imaginary components of M∗ converge from positive values to almost zero at the highest frequencies and lowest temperatures covered for both specimens, with the exception of the real component of the MD specimen which converges to a small but definitely negative value. The analysis of this anomalous behaviour of the MD specimen in terms of the optical retardation time spectrum has ascribed the negative convergence to a negative form birefringence that arises from a dynamic lamellar splaying or bending process responding in phase with the dynamic bulk stress. The dynamic X-ray diffraction studies have revealed the α optical dispersion and possibly the α mechanical dispersion to be mostly attributed to the crystal orientation dispersions involving intralamellar shearing processes, i.e. detwisting and tilting processes of the lamellar segments for the MD and TD specimens, respectively. The optical dispersion, if any, associated with the lamellar splaying or bending process may be expected at higher frequencies or lower temperatures than those covered here to assign the β mechanical dispersion to the interlamellar shearing process.