Swift
Janitor: Efficient Absorption of a Minor Component from the Mixtures
of
Immiscible Liquids by Thermoresponsive Macroscopic and Microscopic
Hydrogels
posted on 2022-12-13, 17:04authored byElena
Yu. Kozhunova, Galina A. Komarova, Mikhail V. Anakhov, Rustam A. Gumerov, Igor I. Potemkin
Polymer hydrogels are known to be
efficient absorbents
of various
aqueous solutions. Along with the hydrophilicity of the polymer network,
the presence of specific functional groups is required for the absorption
of respective solutes. Alternatively, a selective uptake can be realized
without any specific attraction of solutes to the network, which is
shown in this paper. By combining experimental and simulation approaches,
we demonstrated that thermoresponsive poly(N-isopropylacrylamide)
gels and microgels in compositionally strongly asymmetric water/1-octanol
mixtures selectively uptake the minor (1-octanol) component. Initially
swollen in water, the gels substitute water by the organic solvent
upon the addition of its small fraction into aqueous solution. In
turn, for microgels, it was shown that the single particles could
absorb the amount of the organic liquid more than two times higher
than their mass while preserving the colloidal stability. At the same
time, the accumulation of 1-octanol in the networks “switches
off” the temperature response. The mesoscopic computer simulations
revealed a physical reason and molecular picture of the phenomenon.
Absorption of the minor component by the gels is caused by the decrease
in water/1-octanol interfacial tension due to the formation of the
dense polymer layer at the interface. The simulations allowed tracking
the evolution of the size and the internal structure of the single
microgels with changing 1-octanol concentration.