The role of long chains in shear-mediated crystallization was studied by in situ rheo-optical measurements and ex situ microscopic observations. To elucidate the effects of long chains, we prepared model blends in which fractionated isotactic polypropylene (iPP) (denoted L-PP) with high molecular weight (MW) and narrow molecular weight distribution was blended with a metallocene iPP (Base-PP) with lower molecular weight. The concentration of L-PP (c) was varied ranging from 0 to twice the concentration (c*) at which L-PP coils overlap. The crystallization of all blends after cessation of transient shearing was accelerated, while the quiescent crystallization kinetics were not affected by the addition of L-PP. A distinctive change in the development of birefringence after shearing was observed when the wall shear stress (σ w) exceeded a critical value (σ*). Below σ*, irrespective of c, the birefringence after transient shearing increased gradually, reaching a small value at the end of crystallization. Above σ*, a brief interval of shear induced highly oriented growth, manifested in the birefringence after cessation of flow and growing stronger and reaching a large value as crystallization proceeded. Further, the rate of growth of the birefringence exhibited a strong, nonlinear c dependence. The morphology of the skin layer showed a shish kebab type structure observed by TEM for samples subjected to stresses above σ*. The number density and thickness of shish were affected by c and changed drastically at c near the overlap concentration of the long chains. This indicates that the role of long chains in shear-induced oriented crystallization is cooperative (rather than a single chain effect), enhanced by long chain-long chain overlap.

The tricontinuous structure of ABC-type triblock copolymer in bulk at equilibrium was studied by both transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS). Sample is an anionically polymerized isoprene-styrene-2-vinylpyridine triblock copolymer whose volume fraction is 0.22–0.59–0.19 and total molecular weight is 64 000. It was found that computer-simulated images based on tricontinuous structure with two parallel surfaces to the gyroid surface, which is one of the three-dimensionally infinite minimal surfaces agree well with the observed TEM images. Further, calculated diffraction patterns for the same tricontinuous structure well represent the observed SAXS intensity maps on imaging plates. These facts imply that the structure of the present triblock copolymer is the tricontinuous double gyroid structure, whose space group is I4132.

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Miscibility for blends of isotactic polypropylene (PP) and ethylene-d4-propylene random copolymer (EPR)s prepared by copolymerization of propylene and perdeuterated ethylene with metallocene catalyst has been investigated by small-angle neutron scattering (SANS). SANS experiments were conducted for the blends of PP with EPRs containing 19 mol % (D-EPR19) and 47 mol % (D-EPR47) of deuterated ethylene unit at various temperatures. SANS results indicated that most of the blends are in the homogeneous one-phase mixture, and the Flory-Huggins interaction parameter analyzed by the random phase approximation is approximately 5.0 × 10 -3 for the PP/D-EPR47 blend while it is very small and within the range -1.0 × 10 -3 e e 1.0 × 10 -3 for the PP/D-EPR19 blend. It was also revealed that does not change with temperature meaningfully within the temperature range 440 e T e 482 K, while phase separation due to crystallization of PP was observed at 373 K. No domain structure of EPR whose size is in the range of an optical microscope was observed by TEM for the blends quenched from the melt.