Effect of molecular weight of side chain liquid crystalline polymers on properties of liquid crystal physical gels

A series of side chain liquid crystalline polymers (SCLCPs) poly[omega-4'-cyano-(1, 1'-biphenyl)] acrylate (POACB) with different molecular weight were prepared and used as gelator to fabricate liquid crystalline physical gels (LCPGs). The relationship between molecular weight of side chain liquid crystalline polymers and the properties of liquid crystalline physical gels were also discussed in detail. Testing results showed that when the molecular weight of polymers was less than 3.61 x 10(4), the minimum gelation concentration (MGC) of liquid crystalline physical gels decreased from 3 wt% to 0.2 wt% and gel-sol phase transition temperature (T-Gs) increased from 99 degrees C to 185 degrees C with increasing molecular weight. The driving voltage and contrast ratio increased obviously and the off state response time decreased with increasing molecular weight. However, when the molecular weight of polymers was greater than 3.61 x 10(4), the stability and the electro-optical response properties of the liquid crystalline physical gels basically unchanged. The mechanical properties of liquid crystalline physical gels were affected significantly by the molecular weight of polymers. The energy storage modulus of liquid crystalline physical gels increased from 1.6 x 10(3) Pa to 3.1 x 10(4) Pa with increasing molecular weight when the gelator concentration is 6.0 wt%.