Liquid single-crystal elastomers nematic

Static mechanical properties in the vicinity of the nematic-isotropic transition in liquid single crystal elastomers (LSCEs) have been investigated [10, 11]. In Fig. 5 the deformation L/Lq (mon) is plotted as a function of the reduced temperature red- Here Lo(mon) denotes the length of the LSCE at the phase transition temperature of the nematic-isotropic phase transition and... 

Ultrasonic experiments using laser induced phonon spectroscopy have been performed in a nematic liquid single crystal elastomer [48]. The experiments reveal a dispersion step for the speed of sound and a strong anisotropy for the acoustic attenuation constant in the investigated frequency range (100 MHz -1 GHz). These results are consistent with a description of LCEs using macroscopic dynamics [54-56] and reflect a coupling between elastic effects and the nematic order parameter as analyzed in detail previously [48]. 

Kiipfer J, Finkelmann H. 1991. Nematic liquid single crystal elastomers. Makromol Chem Rapid Commun 12 717 726. 

The ability to form monodomain structures makes LC elastomers of interest for a number of optical applications where the optical axis of the polymer must be macroscopically and uniformly aligned. Kuepfer and Finkelmann have reported in detail the formation of what was termed nematic liquid single crystal elastomers [29], which are optically similar to organic or inorganic single crystals. 

Kundler, L Finkelmann, H., Strain-Induced Director Reorientation in Nematic Liquid Single Crystal Elastomers. Makromol. Rapid Commun. 1995,16, 679-686. 

Cordoyiannis G, Lebar A, Rozic B, Zalar B, Kumjak Z, Zumer S, Brdmmel F, Krause S, Finkehnann H (2009) Controllmg the critical behavior of paranematic to nematic transition in main-chain liquid single-crystal elastomers. Macromolecules 42 2069-2073... 

First, the phase transitions of liquid crystals in microcavities of submicrometer size are strongly affected by finite size effects. The nematic-to-isotropic phase transition, for instance, has been shown to become continuous [105, 106, 111]. This phenomenon can be explained by Landau-type models [105-107, 111, 114, 115]. The same effect of a continuous nematic-to-isotropic transition was also observed in bulk liquid single crystal elastomers [116, 117] (see Chap. V of Vol. 3 of this Handbook), whereas the corresponding linear polymer shows a discontinuity of the order parameter at the phase transition. For the elastomers, both a confinement due to the crosslinking and an internal mechanical field, resulting from a second crosslinking performed under mechanical stress, may explain the continuous character of the nematic-to-isotropic transition. 

Komp A, Ruhe J, Finkelmann H (2005) A versatile preparation route for thin fiee-standing liquid single crystal elastomers. Macnnnol Rapid Commun 26 813—818 Ktipfer J, Finkelmann H (1991) Nematic liquid single elastomers. Makromol Chem Rapid Commun 12 717-726... 

Lebar A, Kutnjak Z, Zumer S, Finkelmann H, Sanchez-Ferrer A, Zalar B (2005) Evidence of supercritical behavior in liquid single crystal elastomers Phys Rev Lett 94 197801 1-4 Martinoty P, Stein P, Finkelmann H, Pleiner H, Brand HR (2004a) Mechanical properties of monodomain side-chain nematic elastomers. Eur Phys J E Soft Matter 14 311-321 Martinoty P, Stein P, Finkelmann H, Pleiner H, Brand HR (2004b) Reply to the commentary by Teientjev EM, Warner M on Mechanical properties of monodomain side chain nematic elastomers . Eur Phys J E 14 329-332... 

Fig. 18.3 Thermo- (a) and photo-mechanical (b) effect in LSCEs. Representative opto-mechanical experiment (c) in nematic liquid single crystal elastomers increase of the internal stress generated in the network upon irradiation with UV light (c, left) and decrease of the stress with the time in the dark at a constant temperature, T (c, right)...

---