Hiroshi Kajioka

Morphology and Growth of Single Crystals of Isotactic Polypropylene from the Melt

Isolated single crystals of isotactic polypropylene (iPP) grown from the melt were studied by optical microscopy and atomic force microscopy (AFM). The single crystals had a well-known rectangular shape when crystallized at high temperatures (Tc) above 155°C. The width increased with decreasing Tc, and the shape became hexagonal below 130°C. The single crystals were sectored with thickness difference between them. The growth rate along the a*-axis, Ga*, agreed well with the growth rate of spherulites, as expected. Ga* had two inflection points on the plots against (TΔT)−1. The lower temperature inflection corresponds to the regime II-III transition, and the higher temperature one is accompanied by an inflection of the growth rate in the b-axis direction, Gb, which has been measured for the first time. The inflection of Gb at the lower inflection temperature of Ga* was much smaller than that of Ga* and may not exist. The crystals are basically surrounded with flat surfaces and no indications of kinetic roughening in the regime III were recognized in the AFM images. The inflections of Ga* and Gb caused a complicated shape change of the aspect ratio, having a minimum at around 135°C.

Kinetics of phase separation and coarsening in dilute surfactant pentaethylene glycol monododecyl ether solutions

We investigated the phase separation phenomena in dilute surfactant pentaethylene glycol monodedecyl ether (C(12)E(5)) solutions focusing on the growth law of separated domains. The solutions confined between two glass plates were found to exhibit the phase inversion, characteristic of the viscoelastic phase separation; the majority phase (water-rich phase) nucleated as droplets and the minority phase (micelle-rich phase) formed a network temporarily, then they collapsed into an usual sea-island pattern where minority phase formed islands. We found from the real-space microscopic imaging that the dynamic scaling hypothesis did not hold throughout the coarsening process. The power law growth of the domains with the exponent close to 1/3 was observed even though the coarsening was induced mainly by hydrodynamic flow, which was explained by Darcys law of laminar flow.