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Ferroelectric liquid-crystalline side chain polymers containing polyacrylate or polysiloxane main chains, a mesogenic unit of three aromatic cores and chiral end groups were synthesized and characterized by D.S.C., optical microscopy, and X-ray diffraction. Polyacrylates with a flexible spacer of eleven methylene groups exhibit fast bistable switching in oriented samples (2 to 4pm cells) with response times of some ms at low D.C. voltages, making these polymers interesting for the fabrication of electrooptical devices. Somewhat longer response times were found for the first switchable polysiloxanes. In this case some problems in obtaining well orientated samples have to be solved. IntroductionFerroelectricity in liquid crystals has gained considerable attention in the last few years in both basic research and potential technological applications. The development of bistable fast switching displays exhibiting response times in the range of some p s has created considerable interest in the synthesis and investigation of new ferroelectric materials with high spontaneous polarization. The extraordinary properties found in low molar mass ferroelectric liquid crystals posed the question, as to whether liquid crystalline polymers exhibiting chiral smectic C* phases may also show short switching times. The switching times of nematic liquid-crystalline polymers due to their high viscosity are known to be in the range of seconds, that means two to three orders of magnitude higher compared with low molecular weight liquid crystals. For this reason, the applicability of polymers in high performance fast switching devices seemed to be less promising.Are shorter switching times to be expected in ferroelectric liquid-crystalline polymers because the orientational change of the mesogenic side group in the S,* phase requires only motion on a cone over the double tilt angle? The aim of this work was to find an answer to this question: There are few reports on liquid-crystalline polymers exhibiting chiral smectic C phases [ 1-1 01. Ferroelectric properties, e.g. spontaneous polarization in these polymers, have been established in two types of substances [l, 5, 6, 91. In one case switching times have been reported [9]. To succeed in the synthesis of ferroelectric liquid-crystalline polymers we choose two approaches.

1.2.4‐Triazine werden mittels Zinkstaubs in Eisessig/Alkohol in Dihydrotriazine übergeführt, aus denen bei weiterer Hydrierung keine höher hydrierten Triazine, sondern unter Ringverengung Imidazolderivate entstehen. Bei der katalytischen Hydrierung treten die gleichen Reaktionsprodukte auf. Durch Natrium in Alkohol werden aromatisch substituierte 1.2.4‐Triazine praktisch gar nicht angegriffen, während der aliphatisch substituierte 1.2.4‐Triazinring dadurch zerstört wird. — Bei den hydrierten Triazinen handelt es sich mit größter Wahrscheinlichkeit um 1.2‐Dihydroverbindungen.

Die chiralen cis-und trans-Azoverbindungen 8 ad und 9ad mit para-bzw. ortho-standigen chiralen Seitenketten sowie die trans-Azoxyderivate 17a -d und 18ad werden synthetisiert. Die Asymmetriezentren befinden sich an den C-Atomen 1, 2, 3 oder 4 der Seitenketten. Der EinfluR sowohl der Molekulgeometrie als auch der Entfernung des chiralen Zentrums vom aromatischen Kern auf den Drehsinn und die GanghUhe induzierter cholesterischer Phasen wird untersucht. Bei den cis-Azoverbindungen 9 c und d treten Atropisomere auf.The chiral cis-and frans-azo compounds 8ad and 9 ad with paraor orfho-standing chiral side chains as well as the trans-azoxy derivatives 17a-d and 18a-d are synthesized. The influence of the molecular structure and the distance of the chiral centre from the aromatic nucleus on screw sense and pitch of induced cholesteric phases is investigated. The cis-azo compounds 9 c and d show atropisomerism.. In nematischen Fliissigkristallen lassen sich durch Zusatz von chiralen Verbindungen helixartige, sog. cholesterische Strukturen induzieren'). Enantiomere erzeugen Helixstrukturen gleicher GanghGhe (pitch), aber entgegengesetzten Schraubungssinnesz). In jiingster Zeit wurden Methoden entwickelt, auf einfache Weise den Drehsinn derartiger induzierter Helixstrukturen zu b e~t i m m e n~-~) . Korte, Schrader und Mitarbb. 3, fanden eine Korrelation zwischen der absolutenKonfiguration einer Anzahl chiraler Verbindungen und dem durch sie induzierten Helixdrehsinn. Danach l a t sich aus dem gemessenen Helixdrehsinn die absolute Konfiguration chiraler Verbindungen (mit einem Asymmetriezentrum) ableiten. Hierzu war eine Rangordnung der Liganden am Chiralitatszentrum erforderlich, die von der Raumerfiillung der Liganden ausgeht. Demgegenuber beobachteten Gray und McDonneN4) sowie Heppke und Oestreicher5) an unterschiedlichen aromatischen Systernen mit chiraler Seitenkette ein Alternieren des Helixdrehsinns bei schrittweiser Entfernung des Chiralitatszentrums vom aromatischen Ring, obwohl alle Verbindungen der untersuchten Reihen die gleiche absolute Konfiguration hatten.

Coloured ferroelectric liquid-crystalline side chain copolymers containing 5 per cent and 15 per cent of an azo dye were synthesized and characterized by DSC, GPC and optical microscopy. Order parameters, S, of the azo compound exceeding 0.8 were measured in the frozen smectic phase for the 5 per cent copolymer. The copolymers exhibit fast electrooptic switching in the range of a few hundred microseconds to milliseconds in the S$ phase. Both linear (i.e. electroclinic-like) and ferroelectric switching have been observed. Tilt angles of -19" and spontaneous polarization of -300nCcm-' have been recorded in the S$ phase. IntroductionResearch in ferroelectric liquid crystals has been intense over the past few years. One important advantage of ferroelectric displays compared with the well-known and widely used twisted nematic or supertwist nematic displays is the fast electrooptic switching which is in the range of microseconds. Recently the first examples of switchable ferroelectric liquid crystal side chain polymers have been reported [ 1-41. In favourable cases [3,4] we found response times in the range of some hundred microseconds. Because of the relatively poor anti-shock characteristics of surface stabilized low molar mass ferroelectric display devices fast switching ferroelectric liquid crystal polymers, which form robust films, may find future applications using various birefringent or absorption based electrooptic effects.Coloured liquid crystal displays applying the guest host effect of dichroic dyes dissolved in a nematic liquid crystal were developed some years ago [S]. Recently the guest host effect of dichroic dyes in a ferroelectric liquid crystal [6] and, for the first time, in ferroelectric liquid crystal polymers has been investigated [7]. One drawback to this effect is the poor solubility of dyes in both low molar mass and polymeric liquid crystal materials. By copolymerization of dye monomers a higher percentage of dye content has been achieved in nematic polymers [S]. Ferroelectric liquid crystal dye copolymers, hitherto unknown, might be expected to have both fast switching properties, associated with the ferroelectric phase, and high colour contrast in thin films, because of the higher order parameter and solubility of suitable dyes in the smectic S z layers.