Present work was aimed to investigate supercritical solvent impregnation of thymol into cellulose acetate in order to explore the possibility of developing a new functionalized solvent-free material with antimicrobial properties. Impregnation experiments were carried out with supercritical carbon dioxide at 10, 15 and 20 MPa, and at 35 and 50 degrees C. The time of impregnation was varied from 2 to 44h. Samples of impregnated cellulose acetate were tested against selected microorganisms. Thymol release kinetic studies were performed and obtained results were correlated. The impregnation yield varied from 4.51% to 72.26% depending on the operating conditions and impregnation time. Morphology of the samples changed significantly with the high impregnation yields, implying the impact of thymol on the cellulose acetate. The rate of impregnation was dependent on the impregnation conditions. Strong antimicrobial effect of impregnated samples against Escherichia colt, Staphylococcus aureus and Candida albicans strains with microbial reduction up to 99.9% was observed. Depending on the impregnation yield, samples of impregnated cellulose acetate have continuously released thymol in period from 2 to 21 days. (C) 2014 Elsevier B.V. All rights reserved.