ORIGINAL PAPER Preparation and study of a thermo-responsive membrane using binary liquid crystal mixtures of cholesteryl cetyl ether and cholesteryl oleyl carbonate Massoumeh Bagheri • Parisa Tahririan Received: 15 June 2011 / Accepted: 31 December 2011 / Published online: 29 February 2012 Ó Iran Polymer and Petrochemical Institute 2012 Abstract A facile method for the synthesis of thermo- tropic liquid crystalline cholesteryl cetyl ether (CCE) was carried out from cholesterol and cetyl alcohol using montmorillonite K-10 as an acid catalyst. The aim of this study was to investigate the use of liquid crystalline blends of CCE and cholesteryl oleyl carbonate (COC) with appropriate crystal to smectic phase temperature (T c–s ) just above body temperature as a temperature-modulated drug permeation system. Using 30/70 mol ratio of COC/CCE, a mixture of desirable phase transition temperature was obtained. The phase transition behavior of COC/CCE binary liquid crystalline mixture was established by dif- ferential scanning calorimetry and polarizing optical microsopy. The COC/CCE-embedded cellulose nitrate membrane was used by an in vitro drug penetration studies. Paracetamol and mesalazine were chosen as hydrophobic and hydrophilic drug models, respectively. Paracetamol permeability through the membrane was higher at tem- peratures above the phase transition of liquid crystal (LC) blends (39 °C) than its permeability below the phase transition temperature of liquid crystal blends (30 °C). The drug penetration through LC-embedded cellulose mem- brane was influenced by the pore size of the membrane and therefore the adsorbed amount of LC. There was no pen- etration of mesalazine through that membrane presumably, due to the differences in hydrophilicity of LC-embedded membrane and permeated drug. Keywords Cholesteryl cetyl ether Á Cholesteryl oleyl carbonate Á Binary liquid crystal mixtures Á Thermo-responsive membrane Á Drug delivery Introduction In recent years, extensive efforts have been devoted to the use of potential pharmaceutical devices such as novel drug- delivery systems (DDS), since it facilitates a suitable means of site-specific and/or time-controlled delivery of therapeutic agents. Most polymeric drug-delivery systems have been designed to deliver active ingredients at constant release rates for a long period of time. Approaches, such as swelling-controlled, biodegradable, stimuli-sensitive poly- mers, have received much attention [1, 2]. Stimuli-sensitive or ‘‘smart’’ polymeric systems are polymers that may overcome dramatic property changes responding to small changes in the environment [3]. Stimuli-sensitive polymers may be fabricated in DDS which respond to stimuli, such as temperature [4–6], pH [7–9], photo-irradiation [10, 11], and chemicals [12]. The most important systems, espe- cially from a biomedical point of view, are those sensitive to pH or temperature. Human body presents variations on pH along the gastrointestinal tract as well as in some specific areas like certain tissues (and tumoral areas) or sub-cellular compartments. Thermosensitive polymers with critical temperatures close to the physiological value, i.e., poly(N-isopropylacrylamide) (PNIPAm) offering many possibilities in biomedical field, are materials of great promise in this area [13]. The rapidly increasing interest in functional materials with reversibly switchable physico-chemical properties has led to significant work on the development of stimuli- responsive membranes, for which mass transfer and M. Bagheri (&) Á P. Tahririan Chemistry Department, Science Faculty, Azarbaijan University of Tarbiat Moallem, 53714-161, Tabriz, Iran e-mail: massoumehbagheri@yahoo.com Iran Polymer and Petrochemical Institute 123 Iran Polym J (2012) 21:157–164 DOI 10.1007/s13726-012-0018-1