This is an integrated experimental and theoretical study of the dynamics and rheology of self-crosslinked, slightly charged, temperature responsive soft Poly(N-isopropylacrylamide) (pNIPAM) microgels over a wide range of concentration and temperature spanning the sharp change in particle size and intermolecular interactions across the lower critical solution temperature (LCST). Dramatic, non-monotonic changes in viscoelasticity are observed with temperature, with distinctive concentration dependences in the dense fluid, glassy, and soft-jammed states. Motivated by our experimental observations, we formulate a minimalistic model for the size dependence of a single microgel particle and the change of interparticle interaction from purely repulsive to attractive upon heating. Using microscopic equilibrium and time-dependent statistical mechanical theories, theoretical predictions are quantitatively compared with experimental measurements of the shear modulus. Good agreement is found for the nonmonotonic temperature behavior that originates as a consequence of the competition between reduced microgel packing fraction and increasing interpar-ticle attractions. Testable predictions are made for nonlinear rheological properties such as the yield stress and strain. To the best of our knowledge, this is the first attempt to quantitatively understand in a unified manner the viscoelasticity of dense, temperature-responsive microgel suspensions spanning a wide range of temperatures and concentrations.
Phase behavior of thermoresponsive colloids drives re-entrant plasmon coupling
Institute for Complex Systems, National Research Council（国家研究委员会复杂系统研究所）；Sapienza University of Rome（罗马第一大学）；Synchrotron SOLEIL（SOLEIL同步辐射中心）；Laboratoire Charles Coulomb, CNRS–Université de Montpellier（蒙彼利埃大学-CNRS夏尔·库隆实验室）；Istituto Nazionale per l’Assicurazione contro gli Infortuni sul Lavoro（国家工伤事故保险研究所）
A solvent-flux theory for nonequilibrium swelling dynamics of thermoresponsive microgels
University of Granada（格拉纳达大学）；Institute Carlos I of Theoretical and Computational Physics, University of Granada（格拉纳达大学卡洛斯一世理论与计算物理研究所）；Faculty of Engineering, University of Deusto（德乌斯托大学工程学院）；Center for Nanoscience and Sustainable Technologies (CNATS), and Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide（巴勃罗·德·奥拉维德大学纳米科学与可持续技术中心及物理、化学与自然系统系）
