Effects of 3,3,3-trifluoropropyl content in poly (dimethyl-methylphenyl-methyltrifluoropropyl) siloxane coating on its antifouling performance

Fluorosilicone polymers with a high fluorinated group content are shielded from their interactions with crosslinking agents and solvents by their closely arranged fluorinated groups on their surface. Herein, a series of poly(dimethyl-methylphenyl-methyltrifluoropropyl)siloxanes (PDPFSs) were synthesized using the hydrolysis–polycondensation method to reduce the shielding effect of the fluorinated groups. Dimethyl dimethoxy silane, phenyl methyl dimethoxy silane, and 3,3,3-trifluoropropyl methyl dimethoxy silane (TFMDS) were the main raw materials. The chemical structure of PDPFS and the thermal stability, surface properties, mechanical properties, and antifouling properties of the PDPFS coating were characterized. When the TFMDS content increased from 0 to 40 wt%, the number average molecular weight of PDPFS decreased from 43,380 to 38,433 g/mol and the chemical crosslinking rate of the PDPFS coating decreased from 81.25 % to 68.09 %. An analysis of the surface properties of the PDPFS coating revealed a decrease in surface free energy from 24.22 to 13.19 mJ/m² and an increase in roughness from 0.013 to 0.048 μm. The mechanical properties were examined, indicating that the Young's modulus of the PDPFS coating increased from 0.10 to 0.46 MPa and the average molecular weight between crosslinking points increased from 24,795 to 3285 g/mol. Experimental results revealed that the anti-adhesion efficiency and removal efficiency of the PDPFS coatings was mainly related to the TFMDS content. The anti-adhesion efficiency and removal efficiency were proportional to roughness, Young's modulus, and crosslinking density and inversely proportional to number average molecular weight and surface free energy. Further analysis of the comprehensive antifouling ability of the PDPFS coatings revealed that the antifouling efficiency of the PDPFS coating gradually increased from 16.83 % to 62.12 % with increasing TFMDS content. However, the 3,3,3-trifluoropropyl group exhibited an adverse effect on the hydrolysis–polycondensation and crosslinking reactions when the TFMDS content exceeded 35 wt%. Hence, PDPFS with a TFMDS content of 35 wt% was selected for further research.