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Preparation and Assessment of Chitosan Encapsulated Menthol Microcapsules for Leave-on Conditioners 108 The Journal of the Royal Institute of Thailand Vol. 37 No. 4 Oct-Dec 2012 Abstract Preparation and Assessment of Chitosan Encapsulated Menthol Microcapsules for Leave-on Conditioners Jaruwan Krongsin Multidisciplinary Program of Petrochemistry and Polymer Science, Faculty of Science, Chulalongkorn University Roongkan Nuisin Department of Environmental Science, Faculty of Science, Chulalongkorn University Supaporn Noppakundilograt Department of Imaging and Printing Technology, Faculty of Science, Chulalongkorn University Suda Kiatkamjornwong Associate Fellow of the Academy of Arts, The Royal Institute, Thailand The chitosan/menthol emulsion was prepared via Shirasu Porous Glass (SPG) membrane with an average pore size of 5.2 µm to give the average emulsion drop size of 19.6 ± 2.3 µm with a coefficient of variation (CV) of 11.5%. Another set of 1.5% w/w chitosan emulsion was prepared by dispersing at 14,000 rpm for 90 s. The two emulsions were mixed and the tripolyphosphate-crosslinked chitosan gave the microcapsule size of 27.6 ± 7.2 µm with 26.3% CV. A leave-on hair conditioner was prepared and its rheological property was investigated for application on hair. The chitosan microcapsules, the conditioner base and the leave-on conditioner exhibited a pseudoplastic behavior with a thixotropic hysteresis. Tan delta (G″/G′) as a function of applied temperature of less than 1 indicated that the conditioner was elastic and stable which could be used up to 40˚C. The hair conditioner exhibited a much larger thixotropic hysteresis for at least three cycles. Keywords: SPG membrane, emulsion, conditioner base, leave-on conditioner, viscosity