A Mössbauer Temperature Study of 1,1′-Diacetylferrocene in a Cold Smectic A Liquid Crystal

Abstract

Abstract Fe-57 Mössbauer Effect (ME) measurements were obtained from a 0.2% (by weight) solution of 1,1′- diacetylferrocene in the liquid crystalline material 4-n-octyloxyphenyl-4′-n-nonylbenzoate (8-09). The ME parameters were determined as a function of temperature for the temperature range 110-290K in the crystalline solid phase and 110-240K in the cold smectic A liquid crystalline solution. The “cold smectic A” is defined as the smectic A glass and the supercooled smectic A phase. The ME spectrum was composed of two quadrupule split doublets. The outer doublet was the usual DAF resonance. For T<200 the In recoil-free intensity (f) vs T data for this doublet yielded a Mössbauer-Debye temperature (θLc) of 45 ± 3K which was about 5K lower than for the crystalline phase. Further, it was independent of the direction of a 9KG aligning magnetic field. The smectic A glass-supercooled smectic A transition was determined to be 210K via the deviation of the In f vs. T data from linear behavior. The inner doublet was much less intense than the outer doublet. The angular dependence of the intensity ratios from the two doublets yielded low order parameters (S) of opposite sign. S=0.08 for the outer doublet and S = −0.14 for the inner doublet. The negative value of S suggests that the DAF molecules which contributed to the inner doublet intensity had interacted chemically with the host 80-9 molecules.