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Mileva D.,Martin Luther University of Halle Wittenberg | Androsch R.,Martin Luther University of Halle Wittenberg | Funari S.S.,German Electron Synchrotron | Wunderlich B.,200 Baltusrol Rd.
Polymer | Year: 2010

Wide-angle X-ray scattering has been employed for evaluation of the crystal structure of cold-crystallized random copolymers of propylene with 1-butene. The crystallization procedure included the formation of a metastable mesophase at ambient temperature by quenching the quiescent melt, and the reorganization of the semimesomorphic structure into a semicrystalline structure on subsequent heating/annealing. Research was performed to gain information about incorporation/exclusion of 1-butene chain defects into the crystalline phase when formed via the intermediate step of mesophase formation. The X-ray data suggest that 1-butene co-units up to a concentration of at least 11. mol-% are incorporated into both the mesophase formed on quenching and crystals formed on subsequent heating/annealing according to their concentration in the chain. This observation is in agreement with results obtained on samples which were crystallized directly from the supercooled liquid state, indicating that incorporation of 1-butene co-units into the crystalline phase is not kinetically controlled. Furthermore, information about the α/γ polymorphism and the kinetics of the transition from the semimesomorphic into semicrystalline structure are provided. © 2010 Elsevier Ltd. Source


Mileva D.,Martin Luther University of Halle Wittenberg | Androsch R.,Martin Luther University of Halle Wittenberg | Zhuravlev E.,University of Rostock | Schick C.,University of Rostock | Wunderlich B.,200 Baltusrol Rd.
Molecular Crystals and Liquid Crystals | Year: 2012

A short review about the structure, condition of formation, and reorganization behavior of the mesophase of isotactic polypropylene, summarizing recent work of the authors, is provided. Emphasis is put on the presentation of data collected by novel analysis techniques like fast scanning chip calorimetry (FSC), temperature-resolved X-ray analysis, or temperature-resolved atomic force microscopy (AFM), for quantitative characterization of the kinetics of the liquid-mesophase transition and of the conversion of the mesophase into crystals. In addition, the impact of crystallization of polypropylene via intermediate formation of a mesophase on engineering properties will be highlighted. © Taylor & Francis Group, LLC. Source


Mileva D.,Martin Luther University of Halle Wittenberg | Androsch R.,Martin Luther University of Halle Wittenberg | Zhuravlev E.,University of Rostock | Schick C.,University of Rostock | Wunderlich B.,200 Baltusrol Rd.
Thermochimica Acta | Year: 2011

The perfection, reorganization, and isotropization of the mesophase of isotactic polypropylene were investigated by fast scanning calorimetry (FSC). The analysis was made at different heating rates, to evaluate the isotropization temperature of the initially grown mesophase and of mesophase which has been perfected or even reorganized into crystals. Mesophase formation is paralleled by formation of a rigid-amorphous fraction which was about twice the mesophase content. While the isotropization temperature of the initially grown mesophase is controlled by the temperature of its formation, the isotropization temperature of perfected or reorganized mesophase was independent on the condition of prior formation. Absence of exothermic heat flow during heating suggests that the mesophase converted gradually into crystals due to the fast heating rate. The discussion of data includes new ideas about nucleation, growth, and perfection of the mesophase, involving nanophase to microphase and rigid-amorphous fraction to mesophase transitions. © 2011 Elsevier B.V. All rights reserved. Source


Mileva D.,Martin Luther University of Halle Wittenberg | Androsch R.,Martin Luther University of Halle Wittenberg | Zhuravlev E.,University of Rostock | Schick C.,University of Rostock | Wunderlich B.,200 Baltusrol Rd.
Polymer | Year: 2011

Fast scanning chip calorimetry (FSC) has been employed to study the kinetics of formation of the mesophase of random copolymers of propylene and 1-butene from the glassy amorphous state and its reorganization on heating. The experiments performed consistently prove a distinct decrease of the rate of mesophase formation with increasing concentration of 1-butene chain defects. The time required for isothermal mesophase formation at 300 K is of the order of 0.1 s in case of the homopolymer, while it is prolonged by one order of magnitude to 1 s in the copolymer with 11 mol-% 1-butene. Similar, cold-ordering of amorphous structure on continuous heating at 1000 K s-1 is only completed in the homopolymer while it is almost completely suppressed in the random copolymer containing about 11 mol-% 1-butene. The perfection of the mesophase and/or its reorganization into crystals is faster in the homopolymer than in copolymers containing 1-butene. The critical heating rate for complete inhibition of perfection and reorganization is reduced from about 40,000 K s-1 in the homopolymer to about 10,000 K s-1 in copolymers. The reduced rate of mesophase formation in random copolymers of propylene and 1-butene is attributed to the decrease of the thermodynamic driving force for the phase transformation. © 2010 Elsevier Ltd. All rights reserved. Source

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