Aqueous foam, in the form of biphasic (air/liquid) dispersions, is a metastable system. Amphiphilic molecules/particles are needed to reduce the air/liquid interfacial energy, induce the disjoining pressure in foam film and improve the rigidity of the air/liquid interface, which are crucial to prevent or delay the phase separation. Amphiphilic particles stabilized aqueous foams, kwon as Pickering foams, have the highest stability due to against air bubble disproportionation and coalescence. Regardless of the widely studied inorganic particles (i.e., silica) stabilized foams, bio-based particles, such as cellulose nanocrystals (CNC), have attracted increasingly high interests for Pickering foams requiring applications with biocompatibility and biodegradability. However, due to the intrinsic hydrophilic nature of CNC, CNC have to be partial hydrophobized by chemical reaction or with the addition of other substances. In our study, we have found that chitin nanocrystals (ChNC), with a similar dimension and geometry to CNC, are capable of producing Pickering foams without additional chemical modifications or additives. The presence of amino and acetyl groups on ChNC surfaces are hypothesized to bring ChNC to the air/water interface. Due to the presence of amino groups, the surface chemistry of ChNC is pH dependent. We produced aqueous foams with ChNC of different acetylation degrees and in the presence of different ionic strength. By comparing the foam properties and the packing of ChNC at air/water interface, the role of ChNC in stabilizing Pickering foams will be discussed. The results can serve as a fundamental platform for potential applications of foams in food and drug delivery, as well as for understanding the liquid crystal behavior of ChNC in confined geometries.

Role of chitin nanocrystals in aqueous foam stabilization

2019 Spring National Meeting

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