Hydrophilic-hydrophobic transitions using complexation chemistry

Polyelectrolytes (PEs) and their complexes (PECs) as nanometer-thick coating materials have demonstrated versatile functionalities. However, the conventional Layer-by-Layer (LbL) method is laborious thus limits the industrialization. Researchers have been developing simpler method to produce micrometer-thick PEC coatings. Inspired by them, we focus on an evaporative-induced complexation method by using ammonia (NH₃). The addition of NH₃ allows the weak polycation to remain uncharged that a homogenous solution can be formed with a polyanion. This solution then can be cast onto versatile substrates with controlled film composition and thickness. We have showcased PEI/PAA as a promising oxygen barrier material. Fundamentally, we are trying to understand the brittleness of dry PECs. This brittleness is mainly dominated by the strong ionic interaction instead of chain entanglements. We then keep studying in situ film formation and the introduction of different plasticizers.

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