Prediction and Design of Colloidal Matter using Directional Entropic Forces.

self-assembly of convex and concave particles;depletion driven self-assembly;Chemical Engineering;Materials Science and Engineering;Physics;Engineering;Science;Chemical Engineering

Ahmed, Nayaz KhalidLarson, Ronald G. ;

University of Michigan

关键词: self-assembly of convex and concave particles;    depletion driven self-assembly;    Chemical Engineering;    Materials Science and Engineering;    Physics;    Engineering;    Science;    Chemical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/113334/nkahm_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

We study the effect of entropic forces in the preferential binding of colloidal building blocks towards the assembly of target structures. By using methods developed to calculate the potential of mean force and torque, we quantify the interactions between convex facetted particles with increasing depletant concentration and find that pair-wise entropic interactions are up to a few k_BT. We use these interactions to determine the required depletant osmotic pressure to promote specific binding in different systems.We extend the notion of entropic binding from convex facetted particles to concave dimpled particles - geometrically achieved by reducing the radius of curvature of the entropic feature in a particle;;s shape. By understanding the transition between head-to-head and head-to-tail binding in systems with and without depletants, we evaluate that the robustness required of experimental techniques aimed at synthesizing facetted particles can be reduced in the presence of depletants larger that 0.4 diameters of the colloidal particles.We study the assembly of recently developed experimental building blocks that promise reconfigurable structures through their own shape reconfigurability. This study has necessitated the implementation of new overlap algorithms for Monte Carlo simulations of the equilibrium structures of convex and concave spheroidal particles, particles that can be built as a combination of positive and negative spheres. Through the analysis of densest packing and assembly structures of concave spheroidal particles,i.e. multi-dimpled spheres, we generate geometric considerations that help a priori determine these emergent behaviors of entropic colloidal systems. Finally, through the study of packing and assembly of spherical union particles, we develop a paradigm of entropic repulsive patches, necessary for the design of open crystal structures using entropy. We find open rotator face-centered cubic lattices at small protuberance amounts for all families of particles. At higher packing fractions, we find special crystal structures such as a rotator A15 phase with planar tetravalent particles and a hexagonal close packed phase with hexavalent particles.We believe that these assembly studies of spheroidal particles may provide insight into the assembly of protein building blocks, as proteins are complex systems that assemble under various depleting conditions into different open crystal structures.