Delamination by osmotic swelling of layered materials is generally thought to become increasingly difficult, if not impossible, with increasing layer charge density because of strong Coulomb interactions. Nevertheless, for the class of 2:1 layered silicates, very few examples of delaminating organo-vermiculites were reported in literature. We propose a mechanism for this repulsive osmotic swelling of highly charged vermiculites based on repulsive counterion translational entropy that dominates the interaction of adjacent layers above a certain threshold separation. Based on this mechanistic insight, we were able to identify several organic interlayer cations appropriate to delaminate highly charged, vermiculite-type clay minerals. These findings suggest that the osmotic swelling of highly charged organoclays is a generally applicable phenomenon rather than the odd exemption.
Biodegradable, high‐barrier, flexible and transparent food packaging are required to replace current multilayered, metal‐ or halogen‐containing packaging that is nonrecyclable and nondegradable. An “all‐green” solution for food packaging made of a polylactic acid (PLA) foil (25 µm) furnished with a glycol chitosan‐clay nanocomposite coating (1.4 µm) is presented here that surpasses state‐of‐the‐art high‐performance materials like metallized poly(ethylene terephthalate) or poly(vinylidene chloride) even at harsh conditions (OTR = 0.17 cm3 m−2 day−1 bar−1 at 75% relative humidity). While the barrier side of the foil inhibits bacterial colonization, the uncoated PLA side assures biodegradability. Such a Janus feature in combination with the superb barrier performance renders this waterborne bio‐nanocomposite coating a valuable alternative to conventional less eco‐friendly food packaging materials.
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