Design,Synthesis,characterization And Application Of Comb-like Polymeric Fluorinated Surfactants With Short Fluoroalkyl Chains

Fluorosurfactant is a surfactant in which the hydrogen atoms in the hydrophobic chain of hydrocarbon surfactants are replaced with fluorine atoms in whole or in part.It usually has the characteristics of high surface activity,high thermal stability,high chemical stability,and is both hydrophobic and oleophobic.It can be used as excellent emulsifying,foaming,wetting and dispersing agent,and has many practical applications in production,especially in the fields of pesticide and medicine.Toxicity studies have shown that long-chain perfluoroalkyl derivatives containing more than six CF_n units are bio-persistent,bio-accumulative,and highly toxic,which causing greater environmental hazards.Therefore,it is urgently needed to research and develop new eco-friendly fluorosurfactants.The comb-like polymeric surfactants have the characteristics of easy structure adjustment and good dispersibility and flocculation.Thus,in this paper,we carried out the following three parts of work.（1）Eighteen comb-like fluorosurfactants were prepared by free radical polymerization using different molecular weight poly（ethylene glycol）methyl ether methacrylates（PEGMEMAs）as the hydrophilic monomers and different fluorocarbon chain lengths fluorinated methacrylates（FMAs,（CF₂）_n,n≤6）as the hydrophobic monomers.Their structures were characterized by nuclear magnetic resonance spectroscopy(¹H NMR,¹⁹F NMR),fluorine content determination,and weight determination by gel permeation chromatography（GPC）.（2）The performance,including static surface tension,dynamic surface tension,microscopic characteristics and acute toxicity,of comb-like fluorosurfactants with different compositions and structures was systematically studied,and the structure-activity relationship among composition,structure and surface activity was established.For the first time,it was discovered that the length of the fluorocarbon chain is not the decisive factor of surface activity（capacity and efficiency）.But the surface activity can be tuned by changing the types and feeding ratio of hydrophilic and hydrophobic monomers.The comb-like structure can adjust the structure within a certain range while taking into account surface activity and environmental safety.Acute toxicity experiments showed that this series of surfactants were of low toxicity.The research not only reveals the structure-activity relationship of fluorosurfactants,but also opens up a new direction for the research of short-chain fluorosurfactants.（3）The application of representative comb-like fluorosurfactants b1（both hydrophilic and hydrophobic groups are the shortest chain）,b7（highest surface activity）,b9（both the hydrophilic and hydrophobic groups are the longest chain）as dispersants and commercial dispersants in pesticide water suspensions was compared,where the suspensions included Etoxazole（acaricide）,Indoxacarb（insecticide）,Iprodione（fungicide）,Mesotrione（herbicide）and the new drug,Chloroindolohydrazine（antiviral agent）.The structure-activity relationship between the structure of surfactants and the properties as well as biological activity of water suspension agents was explored through the determination of biological activity and physiochemical properties such as suspension rate,particle size morphology,water dispersion,fluidity,and stability.The results showed that after low temperature,heat storage and freezing storage,the suspension agents had no water separation and no stratification,had good fluidity.Their physical and chemical properties and biological activity were qualified and could meet the requirements of commercial dispersants.