Second Generation ACOMP (SGA) is used to measure, during synthesis, the LCST of copolymers of N-isopropyl acrylamide (NIPAM) and Acrylamide (Am). The polymers are synthesized in aqueous solution below the LCST via a redox-coupled initiation. The instrument consists of a series of temperature controlled light scattering flow cells attached to a custom-built ACOMP system (automatic continuous online monitoring of polymerization reactions). In this work, the ACOMP detector stream provides copolymer composition, molecular weight, viscosity, etc. SGA provides light scattering detection of LCST, allowing correlation of LCST behavior with polymer characteristics as they evolve during the reaction. Light scattering is highly sensitive to aggregation: the absolute Raleigh scattering ratio (I,abs, left-hand side of the figure) indicates LCST almost immediately in the reaction.Several authors have demonstrated that the copolymer system of N-isopropyl acrylamide and Acrylamide is very low drift, and have measured the variation of LCST with composition within this system.The temperature probes of SGA operate on a time scale much faster than the reactions used in this work. As a result, SGA can measure LCST very precisely via a sweep of the temperature controller during the reaction (right-hand side), while the polymer properties remain essentially unchanged. Offline reactions measure the effect of salt on the resulting copolymers.

LCST of NIPAM-Am copolymers: During synthesis characterization and salt effects

245th National Meeting (2013)

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