Synthesis of protective coatings on steel by surface spontaneous polymerization: 2. Studies of the chain propagation mechanism

We have previously reported a new method for applying protective coatings on metal surfaces, the surface spontaneous polymerization process. Polymerization occurs spontaneously on the substrate upon immersion into a monomer solution, forming a layer of uniform coating in situ. A redox mechanism was proposed to explain the spontaneous initiation [1]. In this paper, we report studies of the propagation mechanism involving several monomer systems. It was found that propagation via both a charge transfer complex and addition of free monomers is possible, and also that both mechanisms can be operating at the same time. This is the case for the 4-carboxyphenyl maleimide (4CPMI)/styrene/acrylonitrile system, in which the donor monomer, styrene, forms a charge transfer complex with the strong acceptor monomer, 4CPMI, and copolymerizes alternatingly while the other acceptor monomer, acrylonitrile, is incorporated randomly. The surface spontaneous polymerization process can therefore be used to copolymerize a wide variety of monomers to yield coatings with desired properties.