Introduction Titania pigment dispersion properties are very important for consumer industries, such as paints, papermaking and plastics. If aggregates are present, the end-use properties, including gloss, opacity, tint strength, colour distribution and storage stability, will be highly affected. Dispersion properties can be improved by addition of a dispersant with the dispersant selection largely controlled by its functional group composition. The functional groups are required to interact with the pigment surface as well as to contribute to the repulsion between particles. The interaction between titania pigment and a variety of dispersants has been investigated extensively over the last few years [1–4]. Polyacrylic acid and polyacrylamide homopolymers and copolymers are used as dispersants in a wide range of industries, including mining, water treatment, ceramics, paints and pigments. The use of polyacrylic acid to disperse oxide minerals such as titania and alumina is well established and documented [1, 5, 6]. Adsorption of polyacrylamide on mineral oxides [7], anionic polyacryl- amide onto titania [8–10] and also polyacrylamide copolymers onto talc particles [11] has been studied individually. The aim of this study is to investigate the interaction between polymeric dispersant functional Progr Colloid Polym Sci (2004) 128: 216–220 DOI 10.1007/b97077 Ó Springer-Verlag 2004 Saeed Farrokhpay Gayle Morris Daniel Fornasiero Peter Self Role of polymeric dispersant functional groups in the dispersion behaviour of titania pigment particles S. Farrokhpay Æ G. Morris (&) D. Fornasiero Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia e-mail: gayle.morris@unisa.edu.au Fax: +61-8-83023683 P. Self Adelaide Microscopy, University of Adelaide, Adelaide, SA 5005, Australia Abstract The adsorption of poly- meric dispersants onto titania pig- ment particles has been investigated at pH 9.5 as a function of the type of polymer functional group, using polyacrylic acid and modified poly- acrylamides. The polyacrylamides include homopolymer and copoly- mers with either hydroxyl groups or carboxylate and hydroxyl groups. The experimental methods used were adsorption isotherm, zeta potential, particle size measurements and rhe- ology. The anionic dispersants in- creased the magnitude of the titania pigment particle zeta potential, while the nonionic dispersants had a neg- ligible effect. Both polyacrylic acid and polyacrylamide copolymers al- tered the titania pigment dispersion behaviour, reducing the suspension yield stress and the mean pigment particle size, while the polyacryl- amide homopolymer had a negligi- ble effect on the pigment dispersion properties. Generally the optimum dispersion effect (minimum particle yield stress and particle size) coin- cided with the polymer adsorption density; however, for polyacrylic acid, the maximum dispersion effect occurred prior to maximum adsorp- tion. Acrylamide polymer functional groups adsorbed onto the pigment surface but they were unable to influence the pigment particle dis- persion properties; however, adsorption and dispersion properties were enhanced in the presence of hydroxyl groups. Keywords Titania pigment Æ Polyacrylamide Æ Rheology Æ Zeta potential Æ Polymer functional groups