Structure–property relationships of ‘diluted’ ferroelectric polysiloxanes

Liquid‐Crystalline Colloidal Particles

“…Many LC-acrylate monomers which give rise to nematic phases are known, however, only very few acrylate monomers to obtain chiral smectic C* phases (the precondition for the ferroelectric phase) are known because research on this topic had nearly exclusively focused on ferroelectric polysiloxanes. [7][8][9][10] Concerning the phase sequence, we were aiming at LC-polymers with a T g -value above room temperature. If ferroelectric LC-phases were encountered, a moderate transition temperature between smectic C* and smectic A phase and a high spontaneous polarization was desirable.…”

Cyclic Co-oligomeric Ferroelectric Liquid Crystals with Fast Switching Properties, Wide SmC*Temperature Range and de Vries-type SmA*-SmC*Transition

“…In particular, oligomeric siloxanes possessing pendant mesogenic groups attracted lots of interest, [21][22][23][24][25][26][27][28][29][30][31][32][33] since the siloxane moieties readily give rise to a nano-phase-separated structure as is well known for liquid crystalline polysiloxanes. 11,12 As a result, the temperature range of the smectic phase becomes enlarged, whereas the switching times stay relatively short, due to their oligomeric nature.…”

“…Although these problems can be minimized with polymeric ferroelectric liquid crystals (PFLCs), they limit the switching time and present serious difficulties in the fabrication process due to very high viscosities of polymeric materials. [4][5][6][9][10][11][12] Another problem associated with the use of FLCs are the "Chevron instabilities", 13 which result as a consequence of the smectic layer shrinkage at the smectic A -smectic C* transition. A possible solution for this problem can be liquid crystalline materials with a de Vries-type phase transition, in which the transition happens with a negligible layer shrinkage.…”

Photoresponsive Ferroelectric Liquid‐Crystalline Polymers

“…In mixtures of azobenzenes and a smectic liquid crystal the isomerization process can be accompanied by a segregation of the cis isomers between two smectic layers as described by Lansac et al [7] This however seems impossible in the side-chain polysiloxanes used in our work. Because of their microphase separated structure, [8,9] the cis isomers are "trapped" in the smectic layers, which prevents the segregation. In our previous work we showed that shifts of the phase-transition temperature of up to 17°C can be induced by this photochemical isomerization process (see Fig.…”