DIELECTRIC STUDY OF A FERROELECTRIC SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANE WITH A BROAD TEMPERATURE-RANGE OF THE CHIRAL SMECTIC-C PHASE.2. DOPING EFFECT OF A NONLINEAR OPTICALLY-ACTIVE DYE

Dielectric relaxation behaviour of the guest-host mixture of a ferroel ectric side chain liquid crystalline polymer (FLCP) and a nonlinear op tical (NLO) dye has been investigated with broadband dielectric relaxa tion spectroscopy. The liquid crystal (LC) phases of these guest-host materials were characterized with the differential scanning calorimete r, optical polarizing microscopy, and X-ray diffractometer. No phase s eparation is observed when the doping level of the NLO dye is below 10 wt%. The doping of the NLO dye into the FLCP results in the significan t increase of the relaxation intensity and frequency of the Goldstone mode in the chiral smectic C phase (S-C) Moreover, the NLO dye has hi gh relaxation intensity in the LC phase for such guest-host material. On the other hand, the occurrence of phase separation is observed when the doping level of the NLO dye is 30% by weight. The phase separatio n results in the reduction of the relaxation intensity for both the Go ldstone mode of the FLCP and molecular motion of the NLO dye. The rela tionship between the thermal dynamic behaviour and the environment aro und molecules for such NLO active guest-host material was discussed in great detail. (C) 1997 Elsevier Science Ltd.