Dresden 2017 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 40: Focus: Polymer Crystallization - from Model Systems to New Materials II
CPP 40.8: Vortrag
Mittwoch, 22. März 2017, 17:30–17:45, ZEU 222
Interplay between the Relaxation of the Glass of Random L/D Lactide Copolymers and Homogeneous Crystal Nucleation: Evidence for Segregation of Chain Defects — •Christoph Schick1,2 and Rene Androsch3 — 1Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock — 2Kazan Federal University, 18 Kremlyovskaya street, Kazan 420008, Russian Federation — 3Center of Engineering Sciences, Martin Luther University Halle-Wittenberg, 06099 Halle/Saale
Random L isomer rich copolymers of poly(lactic acid) containing up to 4% D isomer co units have been cooled from the molten state to obtain glasses free of crystals and homogeneous crystal nuclei. The kinetics of enthalpy relaxation and the formation of homogeneous crystal nuclei have then been analyzed using fast scanning chip calorimetry. It has been found that the relaxation of the glass toward the structure/enthalpy of the supercooled liquid state is independent of the presence of D isomer co units in the chain. Formation of homogeneous crystal nuclei in the glassy state requires the completion of the relaxation of the glass. However, nucleation is increasingly delayed in the random copolymers with increasing D isomer chain defect concentration. The data show that the slower formation of homogeneous crystal nuclei in random L/D lactide copolymers, compared to the homopolymer, is not caused by different chain segment mobility in the glassy state but by the segregation of chain defects in this early stage of the crystallization process.