A crosslinking comonomer is essential for producing mechanically stable polyHIPE foams, emulsion-templated polymers with highly interconnected porosities. However, as a result of the large amounts of crosslinking comonomer needed to prevent the collapse of the porous structure, only relatively stiff foams can be produced, in spite of the elastomeric nature of acrylate polymers. The high degree of crosslinking can also interfere with the crystallization of crystallizable monomers. Multifunctional silica nanoparticles, modified using organic alkoxysilanes with polymerizable vinyl bonds, can stabilize water-in-oil high internal phase emulsion (HIPE) templates and crosslink the polymer chains of the resulting polyHIPEs. Localizing crosslinking silica nanoparticles at the oil-water interface in the emulsions has produced a crosslinking density low enough to maintain the highly elastomeric nature or the highly crystalline nature of the resulting polymer foams, but high enough to prevent the porous structure from collapsing.Liquid droplet elastomers (LDEs) were produced using a short-side chain polyacrylate (poly(2-ethylhexyl acrylate)). LDEs are tissue-like elastomeric monoliths that contain around 85% water in the form of individually encapsulated micrometer-scale droplets. Shape memory foams were synthesized by polymerizing (meth)acrylates with crystallizable long side-chains. The nanoparticle crosslinking enables the unrestricted side chain mobility needed for side-chain crystallization/melting, key to their thermo-responsive shape-memory behavior.

Nanoparticle crosslinking in emulsion-templated porous polymers: Toward liquid droplet elastomers and porous shape memory foams

248th National Meeting (2014)

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