Creating Honeycomb Structures in Porous Polymers by Osmotic Transport

Abstract

Understanding why honeycombs are shaped the way they are has moved biologists, physicists, chemists, and mathematicians alike. It was only recently that the honeycombs' shape "at birth" was included in the ongoing discussions: at birth, the cells are spherical but then transform into the well-known hexagons. It was proposed that a flow of wax-driven by surface tension effects-is the reason for this transformation. Our recent work on synthetic polymer foams with honeycomb-like structures points towards a very different mechanism. Just like in honeycomb cells, we observe that a spherical "initial state" transforms into a hexagon-shaped "final state" during polymerization. We have experimental evidence that a concentration gradient arises during polymerization, which transports monomers such that the spherical template becomes a honeycomb structure with walls of homogeneous thickness. The knowledge about this mechanism suggests promising strategies for the development of lightweight materials with optimized mechanical properties.

Toward Functionally Graded Polymer Foams Using Microfluidics

“…The monodisperse foams follow the model by Gibson and Ashby, [31] while the value for the graded foam is lower than predicted by the model. (left) Normalized Young's modulus of polystyrene foams synthesized via foamed emulsion templating plotted against the relative density.…”

Emulsion and Foam Templating—Promising Routes to Tailor‐Made Porous Polymers

“…Chemie statement of Williams et al [30,31] An approach for the production of monodisperse polystyrene foams was presented by Quell et al [9,38,40,41] In these studies,m onodisperse waterin-styrene emulsions were generated by means of am icrofluidic device.T he resulting template was then polymerised and am onodisperse polystyrene foam was obtained. It was shown that the shape of the pores (polyhedral or spherical) can be controlled by the locus of initiation of the polymerisation [38] and that an additional porosity within the pore walls can be produced by initiating the polymerisation within the continuous organic phase.…”

Emulsions‐ und Schaumtemplatierung – vielversprechende Methoden zur Herstellung maßgeschneiderter poröser Polymere

“…Außerdem berichteten sie,d ass das Styrol-zu-DVB-Verhältnis und die Te nsidkonzentration die Porengrçße beeinflussen. [9,38,40,41] In diesen Untersuchungen wurden monodisperse Wasser-in-Styrol-Emulsionen mithilfe der Mikrofluidik gebildet. [4]).…”

“…Ein Wegz ur Herstellung monodisperser Polystyrolschäume wurde von Quell et al vorgestellt. [9,38,40,41] In diesen Untersuchungen wurden monodisperse Wasser-in-Styrol-Emulsionen mithilfe der Mikrofluidik gebildet. Das hieraus resultierende Te mplat wurde anschließend polymerisiert, und man erhielt einen monodispersen Polystyrolschaum.…”