External magnetic field effect on the dye-photoinitiated polymerization of acrylamide

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Abstract
Kinetic measurements of acrylamide polymerization in water, ethylene glycol, their binary mixtures, and a water–glycerol binary mixture have been performed dilatometrically. The reaction was photoinitiated by irradiation of methylene blue (D+Cl–) in the presence of triethanolamine as a reducing agent. The application of a moderate external magnetic field (B⩽ 0.1 T) has led to an increase of the polymerization rate in ethylene glycol or glycerol-containing solutions to δ= 3–17%. Photoreduction of D+Cl– in viscous homogeneous and polymer-containing solutions has also been studied by flash photolysis. The application of a magnetic field resulted in the increase of the concentration of transient free radicals, which initiate polymerization. At B= 0.19 T a significant field effect, i.e. two-fold increase of semiquinone free radical DH˙+, has been found. Magnetic-field effects are described within the frame of the hyperfine coupling (HFC) mechanism. Despite having high dynamic viscosity, polyacrylamide solutions are characterized by low microviscosity and exhibit a relatively small magnetic-field effect. Diffusion rates of low molecular weight compounds in polymeric solutions are discussed.

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