Analysis Method Analysis and study of novel terpolymers composed of acrylamide, mono- charged and double-charged cationic monomers Ricardo Losada, Peter Ka ¨uper, Christine Wandrey * Ecole Polytechnique Fe ´de´rale de Lausanne, Laboratoire de Me´decine Re ´ge´ne´rative et de Pharmacobiologie, CH-1015 Lausanne, Switzerland article info Article history: Received 24 March 2009 Accepted 12 May 2009 Keywords: Cationic polyelectrolytes FTIR Water-soluble polymers Terpolymerization Solution properties Counterion activity abstract The composition of novel terpolymers containing acrylamide (A), acryloyloxyethyl- trimethylammonium chloride (Q), and bis-1,3(N,N,N-trimethylammonium)-2-propylme- thacrylate dichloride (M) was analyzed combining FTIR and potentiometric titration. Calibration with A–Q and A–M copolymers of known composition was the prerequisite for the quantitative analysis of the terpolymers by FTIR. The analysis revealed deviations from the initial monomer feed composition resulting from different monomer reactivity. The differences became more pronounced when M increased in the feed. This suggests lowest reactivity for M. Lower intrinsic viscosity [h] for higher fraction of M in the feed confirmed the suggestion. The low reactivity results from the electrostatic influence of the two charges of M on the chain propagation, yielding shorter chains for more double-charged M in the monomer feed. For all terpolymers, the counterion activity was lower than theo- retically expected and did not correlate with the average charge density. Heterogeneous charge distribution was hypothesized as the reason. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Charged macromolecules, polyelectrolytes (PEL), are widely used for a multitude of applications [1]. They are abundantly provided by nature but can also be synthesized. One group of specialty polymers, which have become particularly important, is synthetic cationic water-soluble polymers. Of these, polymeric quaternary ammonium compounds have historically been the most extensively used cationic PEL. The hydrophilic permanently charged quaternary ammonium groups provide good water solu- bility, and the solution properties correspond to those of a strong PEL [2,3]. Cationic monomers can copolymerize with neutral monomers such as acrylamide to produce PEL of higher molar mass [4] which are frequently employed for solid/liquid separation, such as for water, wastewater, or sludge treatment as flocculating agents [5,6]. PEL are essential for maintaining water as a resource, and the improvement of PEL performance in this application field is important for global sustainable development. The overall environmental and economical impact is affected by factors such as the transportation costs or the fuel demand for sludge drying. To optimize the processes and minimize the costs require a detailed knowledge of the interrelations among PEL constitution, solution behavior and application performance based on comprehensive characterization. The PEL supplier has to offer a series of products designed for specific processes and technologies. PEL parameters such as molar mass, type of charge, charge density and polymer architecture should be adaptable for the final applications. In this respect, successful characterization contributes to the optimization of the synthesis technology [7] and the specific application process. However, charac- terization can present a particular challenge, for example, if the high molar mass and polydisperse PEL of interest is composed of more than two monomers possessing a similar chemical structure, such as in the case of the terpolymers of this study. * Corresponding author. EPFL-LMRP2, AAB 042, Station 15, CH-1015 Lausanne, Switzerland. Tel.:þ41 21 693 96 61; fax: þ41 21 693 96 85. E-mail address: christine.wandrey@epfl.ch (C. Wandrey). Contents lists available at ScienceDirect Polymer Testing journal homepage: www.elsevier.com/locate/polytest 0142-9418/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymertesting.2009.05.004 Polymer Testing 28 (2009) 688–695