Synthesis,Structure-activity Relationship And Application Of Branched Fluorinated Surfactants

PFOA/PFOS is one of the most prominent fluorosurfactants and these compounds have the widest applications.However,such fluorocarbon surfactants have been listed as one of the most difficult to degrade organic pollutants in nature.Developing a new class of highly efficient and environmentally friendly fluorosurfactants to replace PFOS/PFOA fluorocarbon surfactants has become an urgent theoretical issue.Perfluoro-2-methyl-2-pentene(D2)was used as starting material to introducing fluorinated branch for synthesizing non-bioaccumulable alternatives.Cationic,zwitterionic,anionic fluorosurfactants were synthesized using D2 as material,the structure of them were comformed by NMR,MS and FT-IR.The surface performances were measured and the relationship between their structure and properties were discussed in detial.One of the prepared fluorinated surfactant with good surface activities was chosen to mix with other hydrocarbon surfactants,and an aqueous film-forming foams(AFFF)formula was successfully developed.One kind of fluoropolymers was synthesized by solvent polymerization and emulsion polymerization using D2 as material,and the prepared fluoropolymers were successfully applied to fabricate superhydrophobic coatings.Fluorinated surfactants containing CF3CF2CF2C(CF3)2-group and alkyl chains as linkage were successfully synthesized using D2 as starting material.All the steps were easy work-up and reaction conditions were mild.The surface tension tests showed the headgroups have the biggest influence on the surface properties in aqueous solution,with the best being the ammonium oxide.The effect of the length of the linkage on the surface activity varies with the types of hydrophilic groups.Changing the sizes of the same species of headgroup is a useful method for adjusting the properties of surfactants.The cmc value of the fluorinated surfactant with ammonium oxide as headgroup was about 1.73 × 10-2 mol/L and the surface tension in water was 19.93 mN/m at the cmc.A clear synergism was found when it was mixed with APG0810,the use of fluorocarbon surfactant can be reduced by a factor of 100,whereas the surface tension is basically unchanged.Fluorinated surfactants with double hydrophobic chains and containing CF3CF2CF2C(CF3)2-group were successfully synthesized using D2 as starting material.All the values of surface activities of the four novel surfactants were lower than that of sodium perfluorooctanoate.The fluorinated surfactants with double hydrophobic chains showed much better surface activities than the fluorosurfactants with single chain.After add an alkyl chain,the cmc could be reduced more than 200 times to 6.30×10-5 mol/L,and the surface tension is 18.66 mN/m.When add a fluorinated chain,the cmc could be reduced more than 8000 times to 1.74×10-6 mol/L,and the surface tension is 18.42 mN/m.When the alkyl chain length is 7,the surfactant has the same ability with the double fluorinated chain one to reduce the surface tension.Fluorinated surfactants containing CF3CF2CF2C(CF3)2-group and benzene ring as linkage were successfully synthesized using D2 as starting material.The surface tension test showed that the benzene ring as a rigid group can make up for the shortcomings of the shorter fluorocarbon chain less rigid than the long fluorocarbon chain.The introduction of aromatic spacer unit can promote micellization in aqueous solution and packing at the air-water interface,thus improved the efficiency and the ability to reduce the surface tension in water.The introduction of a benzene ring in the linking group is a very effective strategy for improving the surface activity of this type of fluorine-containing surfactants.Toxicity prediction results show that this type of structural fluorocarbon surfactant is low in toxicity and has no carcinogenic and mutagenic potential.An acrylate monomer containing CF3CF2CF2C(CF3)2-group was successfully synthesized using D2 as starting material.Copolymers of the monomer with other hycrocarbon acrylate were prepared through solvent polymerization method and emulsion polymerization method.The water repellence results showed the fluorinated-polyacrylate(PFA)prepared by solvent polymerization have good performances,the water contact angle(WCA)were between 110° to 115°.The fluorinated-polyacrylate(PFA)prepared by emulsion polymerization with core-shell structure showed a larger WCA to 123°.These latex particles have good thermal stability as the T10 is upon 326.4?.Then the PFA emulsion was directly mixed with hydrophilic nano-SiO2 in water and hydrophobic coatings of PFA-SiO2 nanocomposite was fabricated by spraying.The coatings have micro/nano multi-dimensional structure and showed superhydrophobicity.The fabricated films are antifouling and anticorrosion and the fabricated nylon mesh has the function of oil-water separation.One fluorinated surfactant containing CF3CF2CF2C(CF3)2-group and aromatic spacer unit was chose to mix with several commercial hydrocarbon surfactants,all the mixed system showed an excellent synergistic effect.An AFFF fomula was developed by discussing the surface properties,foaming abilities and foaming stabilities of the mixed system.The physicochemical properties and the fire extinguishing performance of the formula were discussed too.The result showed the formula meet the requirements of?GB/T 15308-2006?.The fire extinguishing time is 50 s,burn back time is 12 min,this fomula reached to class IA.The AFFF fomula designed in this article can be used as a substitute of PFOS/PFOA-based AFFF.On the basis of all these encouraging results,we believe that using the carbon-carbon double bond in D2 as the active site to prepare branched fluorinated surfactants is an effective strategy for the development of alternatives to PFOS and PFOA.