Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Crystallization, Nucleation and Self Assembly II

CPP 9.6: Vortrag

Montag, 31. März 2014, 16:45–17:00, ZEU 260

Stability of crystal nuclei in poly(e-caprolactone), studied by fast scanning calorimetry — •Evgeny Zhuravlev, Andreas Wurm, Jürn Schmelzer, and Christoph Schick — Universität Rostock, Institut für Physik, Rostock, Germany

Thermal stability of crystal nuclei was tested in poly(e-caprolactone) at increasing temperatures. The DFSC allows controlled fast heating and cooling of the sample and determination of its heat capacity at scanning rates up to 100,000 K/s. The possibility to change the temperature so rapidly that there is no time for significant recrystallization of the crystals (or nuclei), allows successive isothermal studies of melting, reorganization and recrystallization. Comparison of isothermal crystallization with and without pretreatment at lower temperatures can be realized. The key question we are trying to answer is up to what temperature the various structures can influence on a successive crystallization after disordering. The structures range from configurations having practically unmeasurable latent heats of disordering (melting) to being clearly-recognizable, ordered species with rather sharp disordering endotherms in the temperature range from the glass transition to equilibrium melting for increasingly perfect and larger crystals. Preliminary experiments show, that the PCL nuclei, formed at 210 K (homogeneous nucleation) significantly speeds up crystallization at 250 K, but do not exist anymore at 300 K (Tm = 343 K).