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Acta Polymerica 38 (1987) Nr. 5 260 DONTH, KRETZSCHMAR e t al. : Influence of the chain-end mobility on the melt crystallization GOWSKI, T. M., KRYSZEWSKI, M., and PVCHERZ, J . : Acta Cryst. C 42 (1986) 172. ,Carl Schorlemmer" Leuna-Merseburg, Sektion Physik, DDR-4200 MerseburgHindering and final blocking of the normal melt crystallization in central ethylene oxide (EO) blocks by methyl methacrylate (MMA) end blocks of increasing lengths in ABA type triblock copolymers synthesized anionicallg in a new way are investigated by differential scanning calorimetry and X-ray scattering. Experimental studies of glass transitions, low temperature nucleation, and the morphologic ten-nanometer structure are included. Low percentage amounts of long homo-PEO chains can crystallize in a n ABA matrix which otherwise is not normally crystallizable. It is concluded from the experiments that in our systems with PEO molecular masses up to 50000 g/mol t h e motion of the chain ends is necessary for melt crystallization under normal conditions. DONTH, KRETZSCHMAR et al.: Influence of thr chain-end mobility on the melt crystallization Actr Polymerica 38 (1987) Nr. 5 261 EinfluP der Kettenendenbeweglichkeit auf die Schmelzkristallisation von Ethylenoxid-(B)-Sequenzen in Systemen, die Diblock AB-und Triblockcopolymere ABA mit Methylmethacrylat (A) enthaltenDie Behinderung und letztliche Blockierung der normalen Schmelzkristallisation von zentralen Ethylenoxid( E 0 ) -Blocken durch Methylmethacrylat-(MMA)-Endblocke ansteigender Lange in Triblockcopolymeren vom Typ ABA, anionisch auf einem neuen Weg synthetisiert, wurden mit Hilfe der differentiellen Scanning-Calorimetrie und der Rontgenstreuung untersucht. Experimentelle Untersuchungen des Glasiihergangs, der Keimbildung bei tiefen Temperaturen und der morphologischen Zehn-Nanometer-Struktur werden eingeschlossen. Geringe Mengen (Prozentbereich) langer Homo-PEO-Ketten konnen in einer ABA-Matrix kristallisieren, welche sonst normal nicht kristallisierbar ist. Aus den Experimenten wird geschlossen, daB in den untersuchten Systemen mit PEO-Molekiilmassen bis zu 50 000 g/mol eine Bewegung der Kettenenden notwendig ist fur die Schmelzkristallisation unter normalen Bedingungen. Bnufinue not3ewnocmu ?conqoe yened na Kpucmumaaqim qened amuneno~cuda ( B ) e cuemeMax ~~~~J Z O U H I A X (AB) u mpu6nounb~x cono.nu&epoe A B A c Memuwfiemalcpmamo~ ( A )npOBeAeH0 H3YYeHMe 3aMeAJleHHR R OKOHYaTeJIbHOrO IIpeKpaWeHHH HOpMaJIbHOfi KpHCTaJIJIH3aqMM TpEI6jIOYHbIX COIIoJIRMepOB 3THJIeHOKCHAa (30) M MeTHJIMeTaKpRJIaTa (MMA) IIpH yBeJIR9HBaIOqHXCH AJIHHaX KOHeYHbIX ~JIOHOB C IIOMOqbIO MeTOAa EI PaCCeHHHFI PeHTreHOBCKHX JIyYefi. 06pa31(ar CHHTe3HpOBaJIHCb IHHOHHbIM c11oco6oM. npOBeneH0 3KCIIepHMeHTaJIbHOe H3y9eHHe IIpOUeCCa CTeKJIOBaHHH, HH3KOTeMIIepaTypHofi HyKJleaVRH Ei MOp@OJIOI'H-YeCKOfi CTPYKTYPbI B 06nac.r~ 10 HM. &IHHHbIe UenEI r o~o -n a o IIpR HH3KOM PIX COAepWaHHH MOryT HpHCTaJIJIEI30-BaTbCH B MaTpHqe ABA, KOTOPaFI 0 6~9~0 He KpHCTaJIJIH3yeTCH. CAeJIaH BbIBOA, 9 T O B HalIIHX o6pasqax, COAepWaWkiX n30...

We investigate experimentally and theoretically the isothermic growth of two spherulites of different modification into a supercooled isotactic polypropylene film. The faster growing 3-spherulite grows around the cr-spherulite, and finally the cr-spherulite is symmetrically and completely included in 3. In contrast to literature but in agreement with experimental evidence we find that the grain boundary between the teardropshaped ce-spherulite and the surrounding B-spherulite consists of two parts, where one is always an arc of a logarithmic spiral. This a-spherulite ends always in a vertex. Its angle depends on the ratio of the two growth rates only. Behind the vertex an intrinsic/~-3grain boundary exists, degenerating to a channel in bulk material. The growth fron of the 3-spherulite, which ends on the logarithmic spiral or on the intrinsic grain boundary during growth, consists of an arc of a circle continued by an arc of a logarithmic spirial, too.

Crazes were produced and analyzed in unnotched tensile bars of poly(styrene-co-acrylonitrile) (SAN) and polycarbonate (PC) in creep experiments above TVF (the Vogel temperature). The craze microstructure was investigated as a function of temperature (T) and load (0) by means of small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Contrary to expectation, the scattering vector of maximum intensity ( s , , , ) , which is inversely proportional to the distance between the fibrils of crazes, was not linearly dependent on cr at constant temperature. At the highest stresses (regime III), s , , , was independent of stress, and the average distance between the fibrils reaches a minimum value. At intermediate stresses (regime II), a strong increase of fibrillation energy r w a s detected as the temperature was reduced. In the vicinity of Tw, rreached values of the order of the polymer chain fracture energy. At the lowest stresses (regime I), the energy of fibril formation was independent of temperature and corresponded to the van der Waals surface energy. The molecular motions during fibril formation may be linked to local stress-induced flow processes of polymer chains (regime I) and a-relaxations (regime 11). Increasing stress restricts the range of mobility of macromolecules to shorter and shorter units and a transition from the formation of fibrillated crazes to homogeneous crazes or shear deformation processes occurs at the highest stresses (regime 111). A pressure-temperature diagram was constructed from the transition between the regimes, particularly at negative pressure.

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