Poly(vinylidene fluoride) Containing Phosphonic Acid as Anticorrosion Coating for Steel

Vinylidene fluoride (VDF)-based copolymers bearing pendant phosphonic acid function for potential application as anticorrosion coatings were synthesized via free radical copolymerization of VDF with a new phosphorus containing 2-trifluoromethacrylate monomer, (dimethoxyphosphoryl)methyl 2-(trifluoromethyl)acrylate (MAF-DMP). MAF-DMP was prepared from 2-trifluoromethacrylic acid in 60% overall yield. Radical copolymerizations of VDF with MAF-DMP initiated by tert -amyl peroxy-2-ethylhexanoate at varying ([VDF] 0 /[MAF-DMP] 0 ) feed ratios led to several poly(VDF- co -MAF-DMP) copolymers having different molar percentages of VDF (79–96%) and number-average molecular weights ( M n ’s) up to ca. 10 000 g mol –1 in fair yields (47–53%). Determination of the composition and microstructure of all the synthesized copolymers was done by 1 H and 19 F NMR spectroscopies. The monomer reactivity ratios of this new VDF/MAF-DMP pair were also determined ( r VDF = 0.76 ± 0.34 and r MAF-DMP = 0 at 74 °C). The resulting poly(VDF- co -MAF-DMP) copolymers exhibited high melting temperature (162–171 °C, with respect to the VDF content), and the degree of crystallinity reached up to 51%. Finally, the pendant dimethyl phosphonate ester groups of the synthesized poly(VDF- co -MAF-DMP) copolymer were quantitatively hydrolyzed, giving rise to novel phosphonic acid-functionalized PVDF (PVDF-PA). In comparison to hydrophobic poly(VDF- co -MAF-DMP) copolymers (the water contact angle, WCA, was 98°), the hydrophilic character of the PVDF-PA was found to be surprisingly rather pronounced, exhibiting low WCA (15°). Finally, steel plates coated with PVDF-PA displayed satisfactory anticorrosion properties under simulated seawater environment.