Single-step polyelectrolyte film formation by evaporation-induced complexation

The world consists of all kinds of matter that, chemically, are made of atoms and molecules, interacting through different forces. In the introduction, we discuss a brief history of material science, including the origin of plastics. To explore a new route, reversible interactions, which are individually weaker than covalent bonds, have the potential to cooperatively form a strong network. This thesis, as an example, focuses on electrostatic interactions that allow the formation of polyelectrolyte complexes (PECs). As charged polymers, polyelectrolytes (PEs) are water soluble, but together with oppositely charged PEs, they can form insoluble PECs. Conventionally constructed by layer-by-layer (LbL), polyelectrolyte multilayers (PEMs) show versatile functionalities. However, in our approach, we use an evaporative base to uncharge weak polycations in the solution. In this way, PEC complexation happens during evaporation, allowing the formation of a PEC coating in a single step.
The first successful demonstration of evaporation-induced complexation is the pair: polyethylenimine (PEI) and poly(acrylic acid) (PAA). The resulting films are dense and transparent, while they also show good oxygen barrier properties (