A new series of siloxane liquid crystalline dimers exhibiting the antiferroelectric phase

• In this paper, we report the study of a new series of symmetric chiral liquid crystalline siloxane dimers, their related monomers, and two of those monomers with heptamethyltrisiloxane attached. All the dimers coupled with a trisiloxane show the SmCA phase, which in several cases has a large tilt angle greater than 40° over a wide temperature range, as well as high spontaneous polarisation in the field-induced ferroelectric state. Spacer lengths of 3-6 and 11 carbons between the siloxane central unit and the mesogenic cores were used. Monomers with 3-6 carbons in the spacer showed only orthogonal phases while the monomer with an 11-carbon spacer, as well as the monomers with siloxane attached, have a high tilt angle ferroelectric phase. The materials were characterized by means of DSC, NMR, X-ray diffraction, electro-optical methods (tilt angle and texture characterization) and polarization measurements.

Ämnesord

NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

NATURVETENSKAP  -- Kemi -- Polymerkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Polymer Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

Nyckelord

siloxane

liquid crystals

dimers

antiferroelectric

ferroelectric

tilt angle

ferroelectric

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