Cross-linked cationic starches N-(2-hydroxyl)propyl-3-trimethyl ammonium starch chloride (CQS chloride), N-(2-hydroxyl)propyl-3-trimethyl ammonium starch iodide (CQS iodide), and N-(2-hydroxyl)propyl-3-trimethyl ammonium starch iodideiodine (CQS triiodide) with the degree of substitution (DS) according to cationic groups from 0.04 to 0.62, as well as cross-linked starchiodine complexes were synthesized and tested as potential antibacterial agents. Cationic starch iodine derivatives were obtained during ion exchange reaction between CQS chloride and iodide or iodideiodine anions in aqueous solutions. CQSDS0.3 chloride can form several types of iodine complexes, such as the blue amyloseiodine inclusion complex and ionic CQS+I center dot(I2)m complex (m 1). The antibacterial activity of modified starchesiodine samples against different pathogenic bacterial cultures and contaminated water microorganisms was evaluated. CQS chloride and CQS iodide were found to be bacteriostatic. A strong antibacterial activity was characteristic of CQS triiodides in which molecular iodine is present in both ionic and inclusion complexes. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013