Tailored fluorinated oligo-polystyrene as efficient additive for the hydrophobicity/oleophobicity improvement of styrenic polymers

Abstract

• Perfluorinated polystyrene copolymers were designed and developed as functional additives. • Various fluorinated additives with fluorinated monomer content were synthetized. • The functionality of all synthetized copolymers was validated. • Significant Improvement of hydrophobic and oleophobic surface properties of polystyrene. The surface properties improvement results from both the presence of fluorine and the morphology. • The additive with 19 mol.% of fluorinated monomer has a homogeneous morphology. • The additive with 19 mol.% allows the achievement of higher contact angles. The hydrophobic and oleophobic surface properties of polystyrene can be improved by using specific perfluorinated polystyrene copolymers as additives. In this work, an efficient synthetic route consisting in chemical modification via nucleophile substitution of chlorinated copolymers precursors was optimized. FTIR, 1 H NMR, 13 C NMR and 19 F NMR spectroscopic techniques were used to verify the overall conversion of reactions, characterize the chemical structures and quantify the composition of fluorinated part in the synthetized copolymers. Additionally, the thermal characterizations performed by Differential Scanning Calorimetry and the microstructure revealed by Optical Microscopy and X-ray diffraction, evidenced that the copolymer based on 19 mol.% of fluorinated monomer exhibits a singular properties and seems closer to a periodic copolymer conformation. These singular properties would originate from an interpenetrating conformation and explain the homogeneous morphology for all formulations based on this copolymer in comparison with copolymers based on 4 and 37 mol.% of fluorinated monomer. Finally, the functionality of the synthetized copolymers was evaluated, by measurement of water/oil static contact angles, and also in blend with a commercial polystyrene matrix at various wt.% of additives ranging from 100 ppm to 100 %. The effects of nature and content of copolymers on the hydrophobic and oleophobic surface properties were investigated. For all copolymers, the more the additive content increases, the more the surface properties are improved, obeying a threshold behavior for 4 and 37 mol.% and a quasi-linear behavior for 19 mol.%. Finally, it was evidenced that the surface properties improvement results both from the presence of a critical percentage of fluorine in the polymers blends and its consequence on the morphological properties. The additive based on 19 mol.% of fluorinated monomer allowing the achievement of higher static contact angles even with very low percentages of additive was identified as an optimal additive for improvement of polystyrene surface properties.