The Synthesis of Water Soluble Cationic Microgels by Dispersion Polymerization: Their Performance in Kaolin Deposition Onto Fiber Sedat Ondaral, 1 Mustafa Usta, 1 Menemse Gumusderelioglu, 2 Nergis Arsu, 3 Demet Karaca Balta 3 1 Department of Pulp and Paper Technology, Faculty of Forestry, Karadeniz Technical University, Trabzon 61080, Turkey 2 Chemical Engineering Department, Hacettepe University, Ankara 06532, Turkey 3 Chemistry Department, Yildiz Technical University, Istanbul 34210, Turkey Received 26 October 2008; accepted 22 October 2009 DOI 10.1002/app.31665 Published online 17 December 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The water soluble cationic microgels (CMG), intramolecularly cross-linked cationic polymers of acrylamide (Am) and diallyldimethylammonium chloride (DADMAC), were synthesized with dispersion polymer- ization in the mixture of tert-butanol (TBA)/water in the presence N,N 0 -methylene-bisacrylamide (MBA) as the cross-linker, poly(N-vinylpyrrolidone (PVP) as the stabi- lizer and 2,2 0 -azobisisobutyronitrile (AIBN) as the initiator. The effects of monomer, cross-linker, initiator, and stabi- lizer concentration on both particle size and molecular weight of CMG were investigated. The well dispersed polymer particles were produced in the range of poly dis- persity index 1.1–1.4 and the molecular weight distribution with bimodal. Additionally, the efficiencies of two CMGs in the clay deposition on the bleached kraft fibers were investigated and compared with commercially widely used cationic polyacrylamide (CPAM) and poly-diallyldi- methylammonium chloride (poly-DADMAC). The experi- ments showed that the CMGs were found as the effective flocculation agents and their efficiencies depended on their molecular weight and charge density. V C 2009 Wiley Periodi- cals, Inc. J Appl Polym Sci 116: 1157–1164, 2010 Key words: water soluble cationic microgels; dispersion polymerization; clay deposition; acrylamide; diallyldi- methylammonium chloride INTRODUCTION The use of polyelectrolytes has continuously increased in the various industries: papermaking, water purification, waste water treatment, mineral processing, food, cosmetic industries, etc. 1–4 Among the polymers the cationic copolymers of acrylamide with higher molecular weight have been widely used in these applications because of lower cost and higher efficiency. 5–8 To produce cationic polyacryl- amide, acrylamide, and cationic monomer have been polymerized via previously solution polymerization and recently inverse emulsion polymerization. 8–11 Additionally, they have been prepared with the dis- persion polymerization having attractive advantages over these polymerization techniques: to produce micronsized polymer particles having homogeny size distribution in a single step process. 12–14 In this method, the polymerization of monomer is carried out in the presence of polymeric stabilizer in the convenient reaction mixture in which monomer and stabilizer can easily dissolved. But the reaction mix- ture is nonsolvent for the produced polymer. 15 In the literature, there are very few studies about dispersion polymerization of acrylamide. The most of them have been related to homopolymerization of acrylamide carried out successively by using different initiator, stabilizer, reaction mixture, and synthesis conditions. 16–20 Additionally, recently the copolymer of acrylamide and cationic monomer (acryloyloxyethyl dimethylbenzyl ammonium chlo- ride 12 and 2-methylacryloylxyethyl trimethyl ammo- nium chloride 21 ) have been produced by this poly- merization technique. Addition to polyelectrolyte, the water soluble intramolecularly cross-linked poly- mers, named as ‘‘microgel’’ in the literature, have been synthesized by dispersion polymerization. Compared with linear polymers, water soluble microgels can keep their molecular shape even if they can swell due to their compact structure. 22,23 It is also very likely that these polyelectrolytes will keep their 3D conformation once they are adsorbed to a solid surface. In our previous study in which the efficiency of water soluble cationic microgels (CMG) on the fixation of the dissolved and colloidal substances (DCS) to the both fiber and silicon oxide surfaces was investigated, it was found that CMG having higher charge density and molecular weight Correspondence to: S. Ondaral (ondaral@ktu.edu.tr). Journal of Applied Polymer Science, Vol. 116, 1157–1164 (2010) V C 2009 Wiley Periodicals, Inc.