Silica-diblock fluoropolymer hybrids synthesized by surface-initiated atom transfer radical polymerization

Silica/diblock fluoropolymer hybrids SiO2-g-PMMA-b-P12FMA for coatings were synthesized by the silica surface-initiating atom transfer radical polymerization (SI-ATRP) of methylmethacrylate (MMA) and dodecafluoroheptyl methacrylate (12FMA). Silica surface initiator (SiO2-initiator) was obtained by 10-25 nm fumed silica particles grafted hydrosilylated undec-10-enyl, 2-bromo-2-methyl propionate with a density of 0.573 mmol g(-1). The SI-ATRP approach in this paper displays the diagnostic criteria of controlled radical polymerization by the analysis of H-1 NMR, F-19 NMR and SEC-MALLS analysis, after comparing with the conventional initiator of ethyl 2-bromoisobutyrate (EBiB) for the E-PMMA-b-P12FMA diblock copolymer. Three mass ratios of SiO2-initiator/MMA/12FMA as 1/72.50/18.15, 1/72.50/45.38 and 1/181.26/18.15 were used to obtain the SiO2-g-PMMA-b-12FMA hybrids. The hybrids show 25-30 nm core-shell particles in CHCl3 solution composed of a P12FMA core and PMMA shell, but densely twined together as agglomerated particles. The PMMA-b-P12FMA shell grafted onto silica particles obviously increases the surface roughness of the film (50-500 nm), more than the E-PMMA-b-12FMA film (30 nm), and thereby contributes to the hydrophobic (112-118 degrees) and oleophobic (45-78 degrees) properties of the films. Increasing the P12FMA concentration (1/72.50/45.38) could result in stronger migration of the P12FMA segments onto the film surface, and therefore led to a lower surface free energy (10.97 mN m(-1)), increased advancing and receding for water contact angles (112 degrees and 108 degrees) and the highest cetane contact angles (74 degrees and 70 degrees), the lower water absorption and viscoelasticity, but a high thermostability at 420-450 degrees C.