Effect of number of –CF3 groups in tails of polyester on surface wettability of coatings: synthesis and characterization of PFPE based polyesters with three -CF3 groups in tails

Perfluoropolyethers-based (PFPE) oligomeric polyesters (FOP) with fluorinated tails have emerged as highly stable and nontoxic materials for water and oil repellency, specifically as low surface energy additives to engineering thermoplastics. To investigate the effects of number of –CF3 groups in tails of polyesters on oleophobicity of coatings, FOP with three –CF3 groups in tails (PFoxa) was synthesized via polycondensation reaction of isophthaloyl acid chloride with PFPE alcohols. A model, FOP with a –CF3 group in tails (P3) was used for comparison. To obtain oleophobic surfaces, FOP polyesters were blended with oleophilic polyethylene terephthalate (PET) at different concentrations. The morphology and surface wettability of surfaces were determined by atomic force microscopy and contact angle measurements, respectively. It was demonstrated that when FOPs were added to PET film, they bring significant water and oil repellency to the thermoplastic boundary. By comparing PET/PFoxa with PET/P3 films, it was found that the wettability of films significantly affected by number of –CF3 end-groups. More groups reduce the oil and water repellency due to their conformational entropy penalty on the surface.