Role of Carbon Bridge Length of Organosilicate Precursors on the Atmospheric Plasma Deposition of Transparent Bilayer Protective Coatings on Plastics

We demonstrate the deposition of transparent organosilicate protective bilayer coatings on poly methyl methacrylate (PMMA) substrates with different carbon chain length dipodalsilane precursors using atmospheric plasma deposition in ambient air. The bottom adhesive layer was a hybrid organosilicate coating deposited using either only carbon bridge organosilicate precursor or accompanied with a ring structure 1,5-cyclooctadiene precursor. The top layer was a dense silica coating with high elastic modulus and hardness deposited with only carbon bridge precursor. The adhesion energy of bottom layer increased with increasing carbon bridge length of precursors while the density, hardness, and elastic modulus of top hard layer decreased. The deposited bilayer structure showed similar to 3 times the adhesion energy and four times the elastic modulus of commercial polysiloxane sol-gel coatings.