LIQUID CRYSTALLINE ACHIRAL FERROELECTRIC MATERIALS E. A. Soto Bustamante*, R. Vergara-Toloza, C. M. González Henriquez, G.A. Rodriguez Leyht, D. Saldaño Hurtado Universidad de Chile, Facultad de Ciencias Químicas y Farmacéuticas, Departamento de Química Orgánica y Físico Química Ferroelectricity at the very beginning Lyngourion or Tourmaline (Na,Ca)(Li,Mg,Al)·(Al,Fe,Mn)6 Theophrastus, 2400 BC, Greek philosopher 1707, Curiöse Speculationen bey Schlaflosen Nächten Curious Speculations during sleepless Nigths Johann Georg Schmidt Bring it to Europe from Ceylon 1703 Attracts straw and bits of wood in fire OH O KO ONa O OH K Na (C4H4O6 ) x 4 H2O, 1675 (Elie Siegnette) Town of La Rochelle, France. D. Brewster, “Observation of Pyroelectricity of Minerals”, Edinburgh, J. Sci., 1, 208-14 (1824) KDP,KH2PO4 G. Busch, P Scherer, “A new Seignette- Electric Substance”. Naturwiss., 23, 737-38, TGS Triglycine sulphate 1935. (H2N-CH2-CO2H)3 H2SO4 B.T. Matthias, C.E. Miller J.R. Remeika, Phys. Rev., 104, 849, 1956. 1830, Gustav Rose CaTiO3 Count Lev Aleksevich von Perovski E. Wainer, N. Salomon, Electrical report Titanium Alloys Manufacturing Division Nantional Lead Co. 1938-1943 A. Von Hippel 1945 a b -fase -fase antiparallel dipoles In 1969, induced piezoelectric effects were reported in fluorinated polymers due to strong applied electric field PVDF NO POLEADO POLEADO - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + - - - - - - + - + + + + + - - - - - - - - - - + - + - + + + + - - + + + - - - - - - - - - - + + + + + + + + + + Poled un-poled Ferroelectricity 32 Crystal Classes where 11 are Centrosymmetrics Ferroelectrics 10 with at least a polar 20 non-centrosymmetrics axe Piezoelectrics Pyroelectric Thermodynamic equilibrium where a material can be organized in two different directions Boths directions posses similar energy The ferroelectric state must be defined empirically Ferroelectricity Antiferroelectricity LIQUID CRYSTALS, THE BEGINNING 1888-1935 Cholesteryl Chloride and benzoate Friedrich Reinitzer Otto Lehmann 1888, Uni Prage RO Uni Aachen George Friedel 1922 Daniel Vorländer Nematic: Smectic: Soapy Cholesteric: Uni. Halle thread like (nema, greek) (smegma, greek) from cholesteryl derivatives Nematic Smectic A Smectic C Side Chain liquid crystalline polymer Mesogenic units incorporated in the main chain MCLCP Through aliphatic spacers as side chain liquid crystal polymers SCLCP . Technological applications, nematics 1960-1975 George Heilmeier. 1967 Radio Corp. Of America and James Fergason at Westinghouse Corp. Working temp: 80 °C p,p’-dialcoxybenzoates Hans Kelker, Hoechst, 1969 synthesized MBBA p-methyl-oxybenzilidene-p’-butoxyaniline: Nematic between 20 and 41 °C 1971 Symmetrically and asymmetrically substituted Phenylbenzoates (University of Halle and Merck) p-methoxy-p’-n-butylazoxybenzene. Non-stable material ligth sensitive 1971 James Fergason (Kent State University) Martin Schadt, Wolfgang Helfrich, Switzerland TN Cell or twisted nematic cell 1973 George W. Gray, University of Hull, GB Ciano-biphenyls and –terphenyls Stable nematic untill room temperatures Realibel molecules In 1974, the first FLC (ferroelectric liquid crystal) was reported by Mayer y col. Later on, tousands of new materials appeared O N O O O CH3 H C Polymeric materials were firstly 3 O O C2 H10 O O C 2 H5 reported on 1984 by Shibaev et O O O al. It combines the FLC approach in a SCLCP. After the discovery of the Bistable switching in surface stabilized liquid crystal cells in the 80’s by Clark and Lagerwall and other electrooptics, effects a new brand for technological applications of LC begun. Pseudoferroelectric Sc Methacrylate group and Aromatic Rigid Core (R) Alkoxy Flying Tail (k) Aliphatic spacer (Mn) In 1996 we informed for the first time about a liquid crystalline system without chirality and exhibiting unusual electrical properties based on a low molecular weigth methacrylic monomer mixed in a 1:2 ratio with its polymer Monomer Aromatic rigid core O OH N OCm H 2m+1 OC H O n 2n+1 Alcoxi terminal chain Alifatic spacer H Polymer HO O H C O N PMnRm 2m+1 m OCn H2n+1 O H M O R OH m N O n Cm H 2m+1 OC H O x n 2n+1 P H Liquid crystal laboratory DTA MLP X-Ray Diffraction Small angles region Wide angle region the smectic A or C phase Liquid ot crystal like behaviour 2500 1 2000 1 2 1500 1000 2 ] a.u. [ Intensity Intensity [ a.u. ] a.u. [ Intensity 3 500 3 5 10 15 20 25 30 0 2 [ ° ] 0 2 4 6 8 2 [ ° ] Modulated Pyroelectric Technique Poled samples By cooling without electric field With applied electric field By cooling and heating Piezoelectric technique 3 1 4 1 3 2 2 4 Pyroelectric modulated technique Pyroelectric measurements in PM6R8 mixtures By cooling under an applied electric field Pyroelectric curve Macroscopic polarization 4 500 33 33 3 400 K 300 2 2 2 40 , nC/cm , 200 P, nC/cm P, 51 1 26 26 100 40 51 72 72 0 0 0 50 100 150 200 0 50 100 150 200 Temperatura, °C Temperature, °C Electric field influence O O O O O O O O O H O O H O N N N N N H N H O O O H H H O O O N N N H H O O O O O O O O O -E E=0 +E Mesofase structure .