TY - CHAP

T1 - The Films of Poly(-N-isopropylacrylamide) Nanoparticles on the Water Surface Studied by Surface Rheology

AU - Akentiev, A.V.

AU - Lin, S. Y.

AU - Noskov, B.A.

PY - 2018/9/14

Y1 - 2018/9/14

N2 - The interest in properties of adsorbed and spread micro- and nanoparticles at the liquid-fluid interfaces is mainly caused by their ability to stabilize foams and emulsions. Soft particles (microgel) formed by cross-linked nonionic polymers have attracted special attention. Unlike solid nanoparticles, the soft particles can swell or be contracted under the impact of external conditions. The most of results on the behaviour of cross-linked polymers at the liquid surface have been obtained by the interfacial tensiometry. It was shown that the kinetic and concentration dependences of the interfacial tension have inflection points associated with possible phase transitions in the surface film. The methods of dilatational surface rheology are more informative in respect to conformational transitions in the layers of macromolecules. In this study the dilatational dynamic elasticity of cross-linked poly(N-isopropylacrylamide) microparticle films at the water/air interface was determined as a function of the surface concentration. Two maxima of the surface elasticity close to the surface pressures of about 6 mN/m and 35 mN/m were discovered on the experimental dependency. In the region of the second maximum this dependence is determined by the way of the monolayer formation. At surface pressures above 25 mN/m the compression of the film leads to the formation of a metastable monolayer while an equilibrium and stable layer is formed in the case of consecutive addition of microparticles. In the region of surface pressures corresponding to the second maximum of the surface elasticity the slow relaxation processes occurs in the system with a characteristic time considerably exceeding 10 s. The collapse of the film at surface pressures above 35 mN/m is due to the displacement of microgel from the water surface.

AB - The interest in properties of adsorbed and spread micro- and nanoparticles at the liquid-fluid interfaces is mainly caused by their ability to stabilize foams and emulsions. Soft particles (microgel) formed by cross-linked nonionic polymers have attracted special attention. Unlike solid nanoparticles, the soft particles can swell or be contracted under the impact of external conditions. The most of results on the behaviour of cross-linked polymers at the liquid surface have been obtained by the interfacial tensiometry. It was shown that the kinetic and concentration dependences of the interfacial tension have inflection points associated with possible phase transitions in the surface film. The methods of dilatational surface rheology are more informative in respect to conformational transitions in the layers of macromolecules. In this study the dilatational dynamic elasticity of cross-linked poly(N-isopropylacrylamide) microparticle films at the water/air interface was determined as a function of the surface concentration. Two maxima of the surface elasticity close to the surface pressures of about 6 mN/m and 35 mN/m were discovered on the experimental dependency. In the region of the second maximum this dependence is determined by the way of the monolayer formation. At surface pressures above 25 mN/m the compression of the film leads to the formation of a metastable monolayer while an equilibrium and stable layer is formed in the case of consecutive addition of microparticles. In the region of surface pressures corresponding to the second maximum of the surface elasticity the slow relaxation processes occurs in the system with a characteristic time considerably exceeding 10 s. The collapse of the film at surface pressures above 35 mN/m is due to the displacement of microgel from the water surface.

UR - https://proxy.library.spbu.ru:3693/item.asp?id=42645784&pff=1

M3 - Conference abstracts

SN - 9785965111732

SP - 93

BT - V International Conference on Colloid Chemistry and Physicochemical Mechanics

PB - Издательство Санкт-Петербургского университета

CY - SPb

T2 - V International Conference on Colloid Chemistry and Physicochemical Mechanics

Y2 - 10 September 2018 through 14 September 2018

ER -