Study On The Surface Properties Of Fluorinated(Methyl)Acrylate Copolymer

Perfluoroalkyl(meth)acrylate copolymer has a very low surface energy,and resulting in its special surface transport properties.It can effectively cover the-CF3 group on the surface of the material.Thus,the very low fluorine content of such copolymer allows the material to obtain very excellent surface properties.Also,the low surface energy properties of fluoropolymers can give the material better water repellency,oil repellency,anti-fouling properties and anti-adhesion properties.It has been found that poly(perfluoroalkyl acrylates)containing long side perfluoroalkyl chains(greater than 7 carbon atoms),such as perfluorooctanoic acid(PFOA)and perfluorosulfonic acid(PFOS),are difficult to degrade,and have bioaccumulation and longer biological half-life.Thus,the use of monomers with short side perfluoroalkyl chain to replace long chain length monomers is an inevitable trend.The effect of comonomer with short side chain perfluoroalkyl on the surface energy and surface reorganization of fluorine-containing(meth)acrylate copolymer was systematically studied to find a method for obtaining a stable fluorocopolymer with low surface energy.In the field of basic research,we explored how the comonomer structure affected the surface energy and surface reorganization of the copolymer.In the application research,the microemulsion polymerization was selected to prepare the fluorinated(meth)acrylate fine emulsion,and achieved industrial applications.Also,the comonomer structure was optimized in the microemulsion polymerization.The present work can be summarized as follows.(1)Surface free energy and surface reorganization of perfluorohexylethyl methacrylate/n-alkyl(meth)acrylate copolymers.In this work,we report on surface energy and surface reorganization behaviors of a series of fluorinated copolymers poly(perfluorohexylethyl methacry late)-co-poly[n-alkyl(H or methyl)acrylate],abbreviated as P13FMA-co-P(AnA)or P13FMA-co-P(AnMA),as a function of the lengths of non-fluoroalkyl group in the pendent groups of the comonomers and the presence of hydrogen(-H)or methyl(-CH3)in the ?-position of comonomers.Although the different copolymers that were derived from various comonomers formed different fluorine-enriched concentrations on the gas-solid interface,the increasing chain lengths of the alkyls have less impact the surface energy of the fluorinated copolymers.The methyl at the ?-position of methacrylate monomer results in the significant increase of surface energy.The dynamic contact angle measurements show that the surface reorganization of the fluorinated chains are directly associated with the Tg or Tm of these copolymers.For P13FMA-co-P(AnMA)system,it has higher Tg and lower surface reorganization.However,when the carbon numbers(n)of the alkyl in comonomers are larger than 12,P13FMA-co-P(AnA)shows higher Tm and smaller hysteresis contact angle,as well as more stable low surface energy,compared to those of P13FMA-co-P(AnMA).(2)Effect of groups at ?-position and side-chain structure of comonomers on surface free energy and surface reorganization of fluorinated methacrylate copolymer.Surface free energy and surface reorganization,two essential properties for low surface free energy materials,have been researched by studying the effects of the groups(-H or-CH3)at ?-position and the side-chain structures(flexible or rigid)of alkyl(meth)acrylate on a series of fluorinated copolymers poly(perfluorohexylethyl methacrylate)-co-poly[alkyl(meth)acrylate].The static contact angle,X-ray photoelectron spectroscopy(XPS),and surface tension studies indicate that both the groups at ?-position and the side-chain structures of alkyl(meth)acrylate can significantly influence the arrangement of perfluoroalkyl chains at the interface,resulting in different fluorine-enriched concentrations on the interface,which will finally affect the surface free energy of the copolymer.The dynamic contact angle measurement shows that the surface reorganization of the fluorinated chains are directly associated with the Tg of these copolymers,and decrease with the increasing Tg.All these results show that the copolymers containing-H at the ?-position and flexible side-chain in comonomer have lower surface free energy and higher surface reorganization,while the steric hindrance effects of a-methyl groups and/or rigid side-chain in comonomer allow to the copolymers having higher surface free energy and lower surface reorganization.(3)Effect of sequence structure on wetting behaviors of fluorinated methacrylate polymers based on perfluorohexylethyl methacrylate and stearyl acrylate.In this study,we prepare a series of random copolymers poly(perfluorohexylethyl methacrylate)-co-poly(stearyl acrylate)(P13FMA-co-PSA)and block copolymers poly(perfluorohexylethyl methacrylate)-b-poly(stearyl acrylate)(P13FMA-b-PSA),and systematically investigate the effects of the sequence structure and the content of 13FMA of the fluorinated copolymers on surface free energy and surface reorganization.Static/dynamic contact angle goniometry and water/oil repellency analyses demonstrate that the random polymer P13FMA-co-PSA could not achieve low surface free energy and low surface reorganization at the same time.In contrast,for the block copolymer P13FMA-b-PSA,both low surface free energy and low surface reorganization are acquired simultaneously.The results of X-ray photoelectron spectroscopy(XPS),dynamic contact angle goniometry and differential scanning calorimetry(DSC)reveal the above-mentioned properties.The consecutive 13FMA segments improve the surface fluorine density,whileas the consecutive SA chains enhance the crystallinity of the SA segments,and further hinder the surface reorganization of the perfluoroalkyl groups.Therefore,P13FMA-b-PSA exhibits a higher utilization efficiency of fluorine atoms and a better structural stability than that of P13FMA-co-PSA.