Olga Maria Schimidt Ritter

Disubstituted 3,5‐isoxazolines. An easy route to polymer liquid crystal materials

The synthesis and phase behaviour are described of new side‐chain liquid crystal polyacrylates (9a–9d) with a 3,5‐isoxazoline ring in their mesogenic core. The new homopolymers were synthesised by free radical polymerisation. Phase transition temperatures exhibited dependence on degree of polymerisation and on terminal groups. The resulting materials exhibited typical smectic A mesomorphism.

Synthesis of liquid-crystalline 3,5-diarylisoxazolines

The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines are presented and discussed. These isoxazoline derivatives have been synthesised by reacting oximes with the appropriate 4-substituted styrene dipolarophiles in the presence of N-chlorosuccinimide and pyridine. The isoxazolines 3a–d and 7a–g prepared by this methodology are used as scaffolds for further molecular derivation through a molecular elongation strategy. The selected scaffolds 3a–b and 7f–g were transformed into liquid crystals (LCs) by the addition of an arylacetylene group at the C3 or C5 carbon atoms on the isoxazoline ring by a Sonogashira reaction. The relevant LC compounds 14a–c, 15, 16, 17 and 18a–c were synthesised in fair to good yields. The final compounds display both nematic and smectic A liquid-crystalline phases.

Synthesis and characterization of new chiral liquid crystalline polyacrylates from L-isoleucine

The synthesis of chiral side chain liquid crystalline polyacrylates with a two-stereogenic centre from L-α-aminoacid is described. The chiral tail is 2-chloroalcohol obtained from L-isoleucine and the spacer group has either four or eleven methylene units. The mesogenic moiety is derived from phenyl benzoate. The stereochemistry of the key intermediate (2S,3S)-(+)-4- [1-(2-chloro-3-methyl)pentyloxy]phenyl benzoate (6) obtained by a Mitsunobu reaction was established by single crystal X-ray analysis. This result indicates that the nucleophilic displacement of chiral diazonium salts proceeds with overall retention of configuration. The liquid crystalline behaviour of polyacrylates P13 and P14 was investigated by DSC, optical microscopy, small angle X-ray scattering and depolarized light scattering. The polyacrylate P13, with eleven methylene units in the spacer, exhibits a chiral smectic A phase whereas the polyacrylate P14, with a spacer containing four methylene units, displays a chiral nematic phase.