Polymerization kinetics and morphology changes of thermo-responsive polymer

Application Note #161

SPR peak minimum position shifts to the right due to growth of the polymer chain. The total internal reflection (TIR) angle does not change and thus confirms that no changes in liquid composition (bulk) are occurring during the process.

Multi-Parametric Surface Plasmon Resonance (MP-SPR) measures surface changes in real-time. High sensitivity and minute volumes make the measurement method excellent for thin film characterization providing layer thickness and refractive index. Thermo-responsive poly(N-isopropyl-acrylamide) (PNIPAM) polymerization kinetics was measured during atom transfer radical polymerization (ATRP) in real-time using MP-SPR. Polymer growth was linear with a rate of ~20 nm/min up to 100 nm after which chain termination gradually reduced the growth rate. Brush height during the polymerization was determined without the need to estimate the refractive index. Additionally, brush conformation at different temperatures was studied, showing collapsed polymer at 40°C (69 nm) and extended at 22°C (243 nm).

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