Flocculation properties of a series of cationic polysaccharides, with N-alkyl-N,N-dimethyl-N-(2-hydroxypropyl)ammonium chloride pendent groups attached to a dextran backbone, were evaluated in clay dispersions with respect to length of the alkyl substituent, molar mass, the charge density, and polycation dose. According to turbidimetric results, the alkyl chain length greatly influenced the optimum polymer dose as well as the width of the flocculation window since both increased from an ethyl to a butyl group and decreased for when octyl or dodecyl group was present. The residual turbidity values also varied with the charge density but no dramatic effect was observed with the molar masses investigated. These findings together with the negative value of the zeta potential at the optimum polymer dose and floc size measurements, point to contributions from both patch and bridging mechanisms for the flocculation process. (C) 2010 Elsevier Ltd. All rights reserved.