Inorganic-organic hybrid material coatings by using multifunctional epoxides and twin polymerization

The complex reaction cascade of 2-(3-amino-n-propyl)-2-methyl-4H-1,3,2-benzodioxasiline (APSI) with the tetra-functional epoxide reactant 4,4′-methylenebis(N,N-diglycidylaniline) (MDGA) has been applied to coat polyethylene terephthalate substrates with a nanostructured inorganic-organic hybrid layer. APSI is suitable to undergo twin polymerization and step growth polymerization processes to both poly(3-aminopropyl methyl)siloxane and phenolic resin as well as epoxy resin moieties, simultaneously. The molecular structure formation of the hybrid material formed is proven by solid state 13C and 29Si nuclear magnetic resonance spectroscopy of reference samples prepared as bulk materials. The formation of three polymer structures during one procedure allows the accurate adjustment of the surface morphology that is strongly determined by the ratio of reactant quantities used. In the coatings, at higher MDGA contents, increasingly larger areas of segregated polymer phases up to the micro scale occur. With increasing APSI amount, the surface becomes smoother and more homogeneous. This has a positive effect on the optical properties of the coatings. With a pure APSI layer, a transmission increase of 2% could be achieved.