4-pentyl-4′-cyanobiphenyl. (K15) and 4-heptyl-4′-cyanobiphenyl (K21) as thermo tropic liquid crystals were purchased from Merck Co (Darmstadt, Germany). guncotton membranes (pore size zero.22 μ m, diameter forty nine metric linear unit, and thickness 137 μ m) were obtained from What man (Maidstone, UK). Paracetamol and Methimazole (USP 25) were kindly given by Sobhan pharmaceutical company Co. (Iran) and Alhavi pharmaceutical company Co. (Iran), severally. All alternative solvents and reagents used were of analytical grade.