Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 8: SYMPOSIUM: Polymer networks and beyond: From molecular structure to materials and biological functions III

CPP 8.2: Hauptvortrag

Samstag, 5. März 2005, 14:45–15:15, TU C243

Liquid Crystal Elastomers: Mechanics and Optics — •Heino Finkelmann — Institut für Makromolekulare Chemie, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg

Rubber elasticity is a unique feature of polymer networks or elastomers formed from long polymer chains connected to one another by crosslinkages. An implanting of rod-like mesogenic monomer units into the network chains can induce the liquid crystalline state of the elastomers. The interplay between network chain conformation and liquid crystalline phase creates material with remarkable properties. Detailed investigations proved a direct coupling between chain conformation and anisotropic state of order of the liquid crystalline phase. Depending on the liquid crystalline phase structure eceptional properties are observed: Nematic networks change their macroscopic dimensions when the state of order is modified by external stimuli. This effect can be applied to novel thermo- and opto-mechanical actuators. Chiral nematic (cholesteric) elastomers, because of their birefringence and periodic, helicoidal structure, are 1-d photonic band-gap materials which enable mirrorless lasing. Mechanical deformation of the networks couples to the phase structure and causes a shift of the emission wave length.