Flexible Transparent Hydrophobic Coating Films with Excellent Scratch Resistance Using Si-Doped Carbonized Polymer Dots as Building Blocks

Flexible transparent hydrophobic coating films with excellent scratch resistance have important applications in many fields, especially for optical materials. Herein, a hydrophobic composite coating film was prepared and used as a polymer film protective material by combining 3-glycidyloxypropyltrimethoxysilane (GPTMS)-modified Si-doped carbonized polymer dots (Si-CPDs) with mono-trimethoxysilyl-terminated poly(dimethyl siloxane) (PDMS). The Si-CPDs derived from tetramethyl disiloxane propylamine tetraacetic acid and multi-amino oligosiloxanes were successfully prepared via one-step hydrothermal method and then grafted by GPTMS to obtain modified Si-CPDs (mSi-CPDs). Among them, mSi-CPDs act as a matrix layer, and PDMS acts as a low-surface energy layer. Cross-linking the Si-O-Si network of the coating film was formed through sol-gel chemistry. Driven by the hydrophilic-hydrophobic effect, PDMS trends to aggregate at the film surface, thus avoiding the phase separation which can affect transparency. The highly cross-linked network and the presence of hard silica core provide a high hardness to stand the steel-wool scratch. Flexible polymer chains impart the coating film an outstanding bendability. Introduction of PDMS makes the coating film possess hydrophobicity and anti-graffiti function.