Fabrication pentablock copolymer/silica hybrids as self-assembly coatings

Novel organic/inorganic hybrid for coating material is prepared by the pentablock copolymer PDMS-b-(PMMA-b-PMPS)₂ (PMMDMM) and SiO₂ nanoparticles. PMMDMM is obtained via atom transfer radical polymerization (ATRP) by using polydimethylsiloxane (PDMS) as bifunctional macroinitiator. Poly 3-(trimethoxysilyl)propyl methacrylate (PMPS) is designed as the end block for facilitating the chemical bond of triethoxysilane (Si(OCH₃)₃) groups with SiO₂ nanoparticles produced by tetraethyl orthosilicate (TEOS), and poly (methyl methacrylate) (PMMA) is designed as the middle block for improving the solubility and the film-forming ability of copolymer. The homogeneous dispersion of SiO₂ nanoparticles in the pentablock copolymer matrix enables PMMDMM/SiO₂ to self-assemble into 210nm SiO₂ core/PMMDMM shell elliptic or spherical micelles in tetrahydrofuran (THF) solution. This self-assembled aggregate could provide the film surface with uniform distribution of SiO₂ nanoparticles, obvious hydrophobicity (101-102° water contact angles), lower surface free energy (22.3-21.8nN/m) and lower viscoelasticity. SiO₂ involved into the copolymer matrix could increase the nanostructures roughness. When TEOS is controlled as 20wt.%, the hybrid performs higher glass transition temperature (T_g=113°C) and excellent thermostability (520°C) than PMMDMM (T_g=87°C, 295°C) due to the introduction of SiO₂ nanoparticles. These excellent properties promise PMMDMM/SiO₂ hybrid as the candidate for coating material.