Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Crystallization, Nucleation and Self Assembly I (joint session CPP, DY)
CPP 6.4: Vortrag
Montag, 16. März 2015, 10:30–10:45, PC 203
Experimental test of Tammann's nuclei development approach in crystallization of macromolecules — •Evgeny Zhuravlev1, Jürn W.P. Schmelzer1, and Alexander S. Abyzov2 — 1University of Rostock, Rostock, Germany — 2Kharkov Institute of Physics and Technology, Kharkov, Ukraine
A first attempt to probe the size distribution of homogeneously formed nuclei in polymers was realized employing Tammann's two-stage crystal nuclei development method and fast scanning calorimetry. A transfer heating rate of 500,000 K/s prevents nuclei growth on heating in poly(ε-caprolactone). The employed temperature profile was adapted from Tammann's two-stage crystal nuclei development method implying formation of nuclei at large undercooling (low temperatures) and following their isothermal growth at higher temperatures. Fast scanning calorimetry allowed us to reach the deep supercooling of the melt at 100,000 K/s avoiding heterogeneous and homogeneous nuclei formation and growth. Then crystal nuclei were allowed to form isothermally at the temperature corresponding to the maximum of the steady-state nucleation rate for homogeneous nucleation (210 K for PCL, Tg = 209 K), where both the effect of heterogeneous nucleation and the growth rate are low. The presence of these crystal nuclei and its effect on crystallization was probed by heating the sample to higher temperatures and observation of the overall crystallization process, determining the crystallization half-time. A theoretical explanation of the observations was developed.