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SynopsisAs an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.

The spherulitic growth rate of isotactic polystyrene has been measured in a wide range of temperature by means of a polarizing microscope provided with a hot stage. It was possible to fit the experimental data to theory by choosing a value of 75 for the constant C2 of the WLF equation. The growth rate parameters were compared with those of polyethylene and polychlorotrifluoroethylene. The slowness of crystallization of isotactic polystyrene is mainly a consequence of the lower mobility of the molecules caused by the bulky phenyl groups.

Using X-ray diffraction the structure of crystalline poly(p-phenylene oxide), 9 has been determined. The unit cell is orthorhombic, with the dimensions: a = 8.07 A, b = 5.54 A, and c (fiber axis) = 9.72 A. The unit cell contains four monomeric units. TWO molecular chains pass through a unit cell, one through the center, the other through a corner. Two monomeric units are contained in the fiber identity period. The space group is Pbcn -0:;. The oxygen atoms and the centers of gravity of the phenylene groups are at special positions. The oxygen atoms of one molecular chain are arranged in a zig-zag manner in the (100) plane. The oxygen bond angle is about 124'. The rotation angle of the phenylene groups round the 0-0 axis has been determined by comparing calculated and observed intensities. ZUSAMMENFASSUNG: Die Struktur von kristallinem Poly(p-phenylenoxid), -[ -0 -0 -] , 9 wurde mit Hilfe von Rontgenstrahlbeagungsmethoden ermittelt. Die Einheitszelle ist orthorhombisch; die Dimensionen sind folgende: a = 8,07 A, b = 5,54 A und c (Faserachse) = 9,72 A. Die Einheitszelle enthalt vier monomere Einheiten. Zwei Molekiilketten laufen durch eine Elementarzelle, eine durch das Zentrum und eine durch eine Ecke. Die Periode in der Richtung der Faserachse enthiilt zwei monomere Einheiten. Die Raumgruppe ist Pbcn -Dit. Die Sauerstoffatome und die Zentren der Phenylengruppen befinden sich an speziellen Stellen. Die Sauerstoffatome einer Molekiilkette sind in der (100)-Ebene im Zickzack angeordnet. Der Sauerstoffvalenzwinkel betrkigt etwa 124'. Der Rotationswinkel der Phenylengruppen um die 0-0-Achse herum wurde durch Vergleichen von berechneten und beobachteten Intensitaten ermittelt. *) Part of this paper was presented a t the Microsymposium on Structure of Organic Solids, Prague, Czechoslovakia, 1968, Communication C 4. -[--(r>-O-],

The influence of various thermal pretreatments on the nucleation of isotactic polystyrene has been studied quantitatively by dilatometry. A distinction can be made between nuclei still present above the melting point (“resistant” nuclei) and nuclei created by severe supercooling (“induced” nuclei). The number of spherulites formed has been determined for different combinations of supercooling and crystallization temperatures. The results are interpreted in a satisfactory manner by assuming that in severe supercooling induced nuclei are created, which may grow into effective nuclei at higher temperatures. The crystallization of a severely supercooled polymer is completely governed by these induced nuclei, because they outnumber the resistant nuclei by some orders of magnitude. The number of induced nuclei can be decreased by purifying the polymer (removing catalyst residues). When cooled polymer is heated to temperatures just above the melting point, the induced nuclei are destroyed (“reversible melting”), so that only the resistant nuclei, which are few in number, remain. These resistant nuclei govern the crystallization behavior of a polymer which has not previously been cooled. Their number decreases on heating to temperatures far above the melting point.