Scotti A, Pelaez-Fernandez M, Gasser U, Fernandez-Nieves A
Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany.
Department of Condensed Matter Physics, University of Barcelona, 08028 Barcelona, Spain.
Phys Rev E. 2021 Jan;103(1-1):012609. doi: 10.1103/PhysRevE.103.012609.
We determine the osmotic pressure of microgel suspensions using membrane osmometry and dialysis, for microgels with different softnesses. Our measurements reveal that the osmotic pressure of solutions of both ionic and neutral microgels is determined by the free ions that leave the microgel periphery to maximize their entropy and not by the translational degrees of freedom of the microgels themselves. Furthermore, up to a given concentration it is energetically favorable for the microgels to maintain a constant volume without appreciable deswelling. The concentration where deswelling starts weakly depends on the crosslinker concentration, which affects the microgel dimension; we explain this by considering the dependence of the osmotic pressure and the microgel bulk modulus on the particle size.
我们使用膜渗透压测定法和透析法测定了不同柔软度微凝胶悬浮液的渗透压。我们的测量结果表明，离子型和中性微凝胶溶液的渗透压是由离开微凝胶外围以最大化其熵的自由离子决定的，而不是由微凝胶本身的平动自由度决定的。此外，在给定浓度以下，微凝胶在能量上有利于保持恒定体积而不会明显溶胀。溶胀开始的浓度对交联剂浓度的依赖性较弱，交联剂浓度会影响微凝胶尺寸；我们通过考虑渗透压和微凝胶体积模量对颗粒大小的依赖性来解释这一点。
