Polymerized pickering HIPEs: Effects of synthesis parameters on porous structure

Abstract

A polyHIPE is a highly porous polymer synthesized from monomers within the external phase of a high internal phase emulsion (HIPE). The large amount of difficult to remove surfactant needed for HIPE stabilization can affect the properties of the resulting polymer. A Pickering emulsion is a surfactant‐free emulsion stabilized by solid particles that preferentially migrate to the interface. In this article, the synthesis of crosslinked polyacrylate polyHIPEs based on Pickering HIPEs stabilized using silane‐modified silica nanoparticles is described and the effects of the synthesis parameters on the porous structure are discussed. The silane chemistry, silane content, and nanoparticle content had significant effects on the size of the polyhedral, relatively closed‐cell polyHIPE voids that resulted from aqueous‐phase initiation. Increasing the mixing intensity reduced the wall thickness and produced a more open‐cell structure. The locus of initiation had a significant effect on polyHIPE morphology. Organic‐phase initiation yielded larger, more spherical voids from the more extensive coalescence before the structure could be “locked‐in” at the gel point. Most significantly, the nanoparticles were located within the polymer walls rather than at the interface, as might be expected. The void walls were shown to be an assembly of nanoparticle agglomerate shells that become embedded within the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1516–1525, 2010

Tailoring morphological features of cross-linked emulsion-templated poly(glycidyl methacrylate)

“…Besides the viscosity, [28] the increase in mixing speed influences an increase in shear stress, which causes the formation of smaller droplets of internal phase and also reduces the thickness of the interfacial film, causing more interconnected morphology after polymerisation. [23,29,30] This can be nicely seen from the BET measurements listed in Table 2, where the surface area is increasing with increased stirring rate. Similar results have already been observed previously for MMA polyHIPE material.…”

“…[22][23][24][25] Initiators can be put in either organic or water phase or also in both phases [22,26] and can be induced by thermal decomposition, redox reactions, photolysis, etc. In the case of water-in-oil emulsions (O/W), where monomers and initiator are both soluble in organic phase, the initiation takes place inside the continuous phase, and when initiator is soluble in water phase, the polymerisation starts at the interface of both phases.…”

New composite separator pellet to increase power density and reduce size of thermal batteries

“…Researchers have shown that variables such as emulsion composition (Arditty et al, 2003;Binks and Whitby, 2004;Sturzenegger et al, 2012), mixing speed (Gurevitch and Silverstein, 2010;Sturzenegger et al, 2012), and particle size (Binks and Lumsdon, 2001) have impacts on the Pickering emulsion properties such as porosity and microstructure. When magnesium oxide is used to stabilize the emulsion, processing variables additionally influence the amount of brucite that is created during the sample preparation.…”

“…Pickering emulsion properties such as drop size and porosity are adaptable by varying processing conditions. For example, mixing speed (Gurevitch and Silverstein, 2010;Sturzenegger et al, 2012), particle concentration (Arditty et al, 2003;Binks and Whitby, 2004;Sturzenegger et al, 2012), particle wettability (Akartuna et al, 2008b;Bachinger and Kickelbick, 2010;Chuanuwatanakul et al, 2011;Haase et al, 2011), particle aspect ratio (Vandebril et al, 2010), particle roughness (San-Miguel and Behrens, 2012), and particle size (Binks and Lumsdon, 2001) have all been studied. Such wet emulsions can be shaped, extruded into forms or coated into sheets because of their measurable yield stress Chen et al, 2012).…”

Achieving Interconnected Pore Architecture in Injectable PolyHIPEs for Bone Tissue Engineering

“…Recently, the Silverstein group published studies describing the effect of the locus of initiation on pore architecture and properties. [33][34][35][36] The authors proposed that organic-phase initiation resulted in larger, spherical, interconnected pores and an increased loss modulus relative to aqueous-phase initiation. 34 However, a mechanistic description of the effect of locus of initiation on the resulting macromer densification forces and the corollary effect on interconnect formation was not described.…”