Phase stability of dispersions of hollow silica nanocubes mediated by non-adsorbing polymers
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THE EUROPEAN PHYSICAL JOURNAL E
Regular Article
Phase stability of dispersions of hollow silica nanocubes mediated by non-adsorbing polymers ´ Gonz´ F. Dekker1 , A. alez Garc´ıa1,2 , A.P. Philipse1 , and R. Tuinier2,a 1
2
Van ’t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute for Nanomaterials Science, Utrecht University, Padulaan 8, 3584 CH, Utrecht, The Netherlands Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry & Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands Received 4 May 2020 and Received in final form 27 May 2020 Published online: 19 June 2020 c The Author(s) 2020. This article is published with open access at Springerlink.com Abstract. Although there are theoretical predictions (Eur. Phys. J. E 41, 110 (2018)) for the rich-phase behaviour of colloidal cubes mixed with non-adsorbing polymers, a thorough verification of this phase behaviour is still underway; experimental studies on mixtures of cubes and non-adsorbing polymers in bulk are scarce. In this paper, mixtures of hollow silica nanocubes and linear polystyrene in N ,-N dimethylformamide are used to measure the structure factor of the colloidal cubes as a function of nonadsorbing polymer concentration. Together with visual observations these structure factors enabled us to assess the depletion-mediated phase stability of cube-polymer mixtures. The theoretical and experimental phase boundaries for cube-depletant mixtures are in remarkable agreement, despite the simplifications underlying the theory employed.
1 Introduction Ordered structures prepared from functional colloids have multiple applications, and are expected to play an important role in the development of new technologies. Colloidal solids obtained from micron-sized particles exhibit a photonic bandgap [1], while plasmonic nanoparticle solids can be applied as highly sensitive sensors [2]. There are different methods to prepare colloidal solids [3, 4], but most of the available techniques require high particle concentrations or operate under out-of-equilibrium conditions [3,5,6]. To form assemblies with desired structural properties, a delicate control over the colloidal interactions is required. Particle-particle interactions are affected by the addition of non-adsorbing polymers, often termed depletants [7]. Due to configurational entropy loss of the depleted polymer chains near the surfaces of the colloidal particles, the polymer segment density close to the colloidal particles is lower than in bulk [8]. The polymer concentration profile defines the depletion zones around colloidal particles in presence of non-adsorbing polymers [9, 10]. Whenever overlap of depletion zones occurs, there is an osmotic pressure difference between the bulk and the overlapping volume, leading to a net attraction between the colloidal particles. This depletion attraction a
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between colloidal particles is, to a certain degree, tuneable via the depletant co
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