Regensburg 2013 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 41: Colloids and Complex Liquids I
CPP 41.10: Vortrag
Donnerstag, 14. März 2013, 12:45–13:00, H40
Phase behavior of plate-like block copolymer single crystal suspensions — Chunbo Jiang1, Haiying Huang1, Cungui Ma1, Tianbai He1, and •Fajun Zhang2 — 1State Key Laboratory of Polymer Physics and Chemistry, CIAC, CAS, China — 2Institut für Angewandte Physik, Universität Tübingen
We have studied the influence of particle size and tunable lateral interaction on the isotropic-nematic phase transition of a plate-like colloidal system. The particles are single crystals of a block copolymer PS-b-PLLA prepared using a self-seeding procedure in solutions [1]. These lozenge shape crystals have uniform thickness and narrowly distributed lateral size. The phase behavior is characterized under crossed-polarizers for all systems with size ranging from 500 to 4000 nm. It is surprising to see that the I-N transition occurs at a much lower volume fraction than the theoretical predicted value. However, if adding ethanol into the solution the I-N transition is significantly suppressed. These results demonstrate the existence of a lateral attraction between crystals and it is most likely due to the polar interaction between the crystalline PLLA. Because of the sandwich structure of the crystals, the confinement by the amorphous PS layers renders the attraction highly orientation dependence. In this way, larger plate-sheets are formed via lateral attraction and give a much lower critical volume fraction. To further demonstrate this highly orientational attraction, we have further prepared a composite single crystal with a PLLA homopolymer. Indeed, the resulting liquid crystalline phases show much less horizontal ordering. [1] Jiang C. et al. Langmuir 2011, 27, 4351