Design Of Emulsion-Templated Mesoporous–Macroporous Polyurea Gels and Aerogels AITranslate

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DOI：https://doi.org/10.1021/acsapm.9b00762

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A sol–gel process is used in this work to obtain porous materials with three-dimensional, chemically cross-linked solid networks from polyurea with their meso- and macropores filled with a liquid achieved via an oil-in-oil (O/O) emulsion. These materials are suitable for transport of nutrients with potential applications as tissue scaffolds. The proper design of coexisting, interconnected networks of meso- and macropores is key to success. This paper presents synthesis of polyurea (PUA) gel in dimethylformamide (DMF) from aromatic isocyanate and water mixtures with inherently produced meso- and macropores. In conjunction, a set of pores with diameters of a few tens of micrometers, defined as macrovoids, are introduced via O/O emulsion-templating using n-heptane. The stability of the O/O emulsion is an issue in view of the relatively long gel time of 23–75 min and high volume fraction of n-heptane. This is mitigated by using high concentration of surfactants. The presence of water as a reactant also changes the interfacial conditions. The results show that the polyethylene–polypropylene block copolymer surfactant at high concentration exerts significant influence on gel time, polymer strand size in the gel network, stability of the emulsion, and specific surface area of the solid network. An increase of n-heptane volume fraction leads to an increase of porosity aided by an increase of macrovoid fraction. The scanning electron microscope images reveal open porous interconnects among macrovoids and denser polymer strands at the surfaces of n-heptane droplets.