Dynamic elasticity of films formed by poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) microparticles on a water surface |
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Authors: | A V Akentiev G S Rybnikova A A Novikova K A Timoshen I M Zorin B A Noskov |
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Institution: | 1.St. Petersburg State University,St. Petersburg,Russia |
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Abstract: | Surface dilatational dynamic elasticity ε of films formed by cross-linked poly(N-isopropylacrylamide) microparticles on a water/air interface has been determined as a function of polymer surface concentration Γ. The experimental dependences exhibit two maxima of ε at surface pressures π of nearly 6 and 35 mN/m. In the region of the second maximum, the pattern of the dependence is governed by a method used to vary Γ. At π > 25 mN/m, film compression leads to the formation of a metastable monolayer, while the gradual addition of a microparticle dispersion results in the establishment of equilibrium between the monolayer and surface aggregates. In the region of π values corresponding to the second maximum of ε, slow relaxation processes with a characteristic time substantially longer than 10 s occur in the system. At π > 35 mN/m, the film collapses due to the displacement of microgel particles from the water surface. |
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