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Thermosensitive polymers are gaining increasing interest due to their possible applications as drug delivery systems, flotation agents in mineral ore processing or flocculants in wastewater treatment. Lower Critical Solution Temperature (LCST) is a crucial parameter of thermoresponsive polymers. In this work the comparison of four different methods of LCST determination, i.e. transmittance, viscosimetric, Dynamic Light Scattering (DLS) and pH measurement, are presented. They are found to be complementary and each of them is shown to fail under certain condition. For the purpose of this research a cationic copolymer of poly(N-isopropylacrylamide) with diallyldimethylammonium chloride was synthesized. Moreover two reference polymer samples were investigated. [ABSTRACT FROM AUTHOR]

Abstract: Flocculation process based on water soluble polymers as flocculating agents is still intensively researched nowadays, despite the introduction of these materials about fifty years ago. Dual polymer flocculation or application of new, more sophisticated macromolecules is proposed as a new approach. Simultaneously, more detailed mathematical models of flocculation are developed. The employment of polymer degradation model in population balance equations (PBE) is proposed in the paper. The suspension of chalk in distilled water was flocculated using three types of ultrasonically conditioned commercial flocculants. The experiments were performed using an apparatus for on-line determination of particle size distribution (PSD). The obtained results were compared with simulations using the Class Method. It was proved that the kinetic constant in the aggregation kernel can be described by a function similar to the one showing a change of mean molecular weight of polymer with sonication time. [Copyright &y& Elsevier]

Abstract: The impact of suspension heating method on the flocculation process using thermosensitive polymer is reported in this paper. In experiments a model suspension of chalk in RO water (purified by Reverse Osmosis) was destabilized using a copolymer of N-isopropylacrylamide (NIPAM) andcationic diallyldimethyl ammonium chloride (DADMAC). The measurements were made using a laboratory setup consisting of a mixing tank with four baffles, Rushton turbine, laser particle sizer Analysette 22 by Fritsch and a system of pump and thermostating devices. Two different modes of heating were used. In the first case the temperature of the system was gently raised above the Lower Critical Solution Temperature (LCST) using an electrical heater placed inside the tank, while in the second case the system temperature was rapidly raised by an injection of hot water directly into the tank. It was proven that heating method as well as the polymer concentration was crucial to the shape and size of created flocs. [Copyright &y& Elsevier]

Abstract: The influence of temperature on particle size distribution of chalk suspension in the presence of a thermosensitive flocculant based on N-isopropylacrylamide and 3-(acryloyloxy)propanoic acid was investigated. No aggregation was observed at room temperature upon the addition of the polymer. When the system was heated, flocculation took place and the mean particle diameter was found to be temperature dependent. The polymer dosage influence on the process was examined. In higher polymer concentration the investigated process was fully reversible, i.e. aggregates broke upon cooling. The possibility to control particle size by temperature adjustment is discussed and the process'' model is proposed. [Copyright &y& Elsevier]