Heinrich Kapitza

Field dependent soft and goldstone mode in a ferroelectric liquid crystal as studied by dielectric spectroscopy

Abstract Broadband dielectric spectroscopy (frequency range 10 -1 –10 7 Hz and temperature range 100 to 450 K) was used to analyze in detail the frequency and temperature dependence of the soft and the Goldstone mode in a ferroelectric liquid crystal.

Orientability of Crosslinked and of Chiral Liquid Crystalline Polymers

Abstract Crosslinked liquid crystalline (l.c.) polymers can be reversibly oriented in the l.c. phase by small mechanical strains. This property makes it very interesting to investigate chiral l.c. phases with a helical superstructure (cholesteric and chiral smectic C*). These phases can e.g. be realized with new combined main chain / side group polymers. In order to give a high spontaneous polarization to the polymers in the chiral smectic C* phase, polymers with a dipole moment at the chiral center were synthesized.

Softmode at the ferroelectric/non ferroelectric phase-transition in a liquid crystalline polymer

Abstract Broadband dielectric spectroscopy covering the frequency range from 10−1 to 107 Hz was used to analyse the softmode at the phase transition from a ferroelectric highly ordered and tilted smectic phase to the smectic A—phase in a combined side group main chain liquid crystalline polymer.

Anomalous current and electrooptic response in a polyacrylate ferroelectric liquid crystal with large spontaneous polarization

Abstract A side-chain polymer exhibiting a chiral smectic phase was investigated. Due to its anomalous current and electrooptic responses, we discuss the possibility of antiferroelectric order in the polymer, and compare its behaviour with a low-molar mass antiferroelectric substance. In particular, we study the birefringence modulation resulting from the field induced antiferroelectric-to-ferroelectric transition, and determine the induced polarization by the field reversal method.

A molecular gyroscope based on the goldstone mode in ferroelectric liquid crystals

Abstract Based on the analysis of the molecular assignment of the dielectrically observable Goldstone mode in ferroelectric liquid crystals (FLC) with a chiral smectic c(S ∗ c ) phase, a planar, four-electrode microstructure was developed. It allows one to realize, driven by phase-locked, 90° shifted rotating electrical fields, a molecular gyroscope of rotation frequencies up to 5 kHz, providing new FLC applications.

Field dependent Goldstone-mode in ferroelectric liquid crystalline polymers

Abstract Broadband dielectric spectroscopy covering the frequency range from 10−1 to 107 Hz was used to analyze the two ferroelectric modes, Goldstone– and soft—mode, in polymeric liquid crystals. The Goldstone mode can be continuously suppressed by the application of a DC bias field in close analogy to low molar mass systems.

Characterization of a novel blend consisting of a liquid crystalline polymer and a photopolymerized crosslinked acrylic matrix

Abstract A blend of a novel soluble main chain liquid crystalline (LC) copolymer with a low molecular weight photopolymerizable trifunctional acrylate was formed. X-ray diffraction studies revealed that the structure of the mesophase was disrupted upon addition of the monomeric acrylates. However, once the blend was exposed to ultraviolet radiation and post-cured, a densely crosslinked semi-interpenetrating network of the second kind (semi-IPN-II) was formed, and the original structure of the mesophase was restored. The unique feature of this crosslinked blend is that the LC copolymer can undergo transitions from its LC to isotropic phase in the presence of the densely crosslinked acrylate matrix. In addition, this blend has mechanical integrity at temperatures well above the LC to isotropic transition region.