Ferroelectric LCPs

However, due to the helical structure of the SmC mesophase, no net spontaneous polarization results. Macroscopic nonvanishing polarization is only obtained when the helix is unwound. This requirement has been a severe limitation for the determination of Ps, and we had to wait until 1988 for the first observation of ferroelectric switching in a side chain SmC LCP [65]. Even now, the measurement of remains delicate and its reliability is directly connected to the quality of the uniform alignment achieved. 

Electroclinic behavior has been recognized in few SmA LCPs [77] and response times in the sub-millisecond range have been observed. But, surprisingly, the SmC X phase of polyacrylate V-11 exhibits an electroclinic switching process with a short response time (200 p s) that is changed into a ferroelectric one as the temperature is raised. Moreover, the electroclinic-ferroelectric transition is shifted towards lower temperatures when the voltage is increased (Fig. 20). 

The orientation of liquid crystals can be influenced by an electric field. This property makes LCPs attractive for LCDs. Some liquid crystals undergo a spontaneous electric polarization even in the absence of an external electric field. This phenomenon is referred to as a ferroelectricity. 

Initially, research focused on the possible display properties of smectic A and nematic, linear side-group polysiloxanes however, the very high viscosity inevitably means that the response times will be slow compared with low-molar-mass systems. Recently, ferroelectric polysiloxane and polyacrylate LCPs, such as (22, 5f 30°C 55°C 120°C I and 23, 15°C S 103°C 124°C /), and composites of them... 

A liquid crystal device comprising ferroelectric liquid crystal material aligned by a liquid crystal polymer (LCP) network layer under 20 nm thick, which itself was aligned by a photo-oriented linearly photopolymerized (LPP) layer under 20 nm thick, exhibits low voltage drop over the aligning layer and has a remarkable contrast ratio. 

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