Fabrication Of High-performance Fluoro-porous Polymer Via High Internal Phase Emulsion Stablized By Multi-factor

Porous polymer foams play an important role in a wide range of applications such as rapid oil/water separation,supporting materials for growth of tissues,catalyst attachment,controlled release matrices,separation membranes,heavy metal ion collectors,and other application.Recently,highly porous polymer materials prepared by high internal phase emulsion?HIPE?templating appeal to many researchers.HIPE template serves as a method to produce polymer materials with a porous structure.Monomers?oil?are used as the external phase and water as the internal phase and the volume fraction of the internal phase may range from 0.74-0.99 with respect to the total emulsion volume.Candidate monomers for HIPE include styrene,acrylate,divinylbenzene,glycidyl methacrylate and so on.Recently,the introduction of fluoro-monomers into the polyHIPE system has shown that polymer monoliths can be given the advantages of e.g.chemical/oxidative stability,thermal/environmental stability and excellent surface properties.Although fluoro-HIPEs are available in this method,further efforts are required to improve the stability of fluorinated emulsion.Currently,the pore size of the polymer materials based on HIPE templates,including fluoro-polyHIPE,is much larger than 10?m,resulting in a low specific surface area and poor mechanical properties.In this paper,a method of fabricating fluoro-porous material was studied.The effects of various factors on the stability of fluoro-HIPE were explored.After the polymerization,a fluorine-containing porous material having more excellent properties was obtained.Fluoro-porous materials and fluorosilicon hybrid materials with excellent mechanical properties and high specific surface area were prepared by the synergistic action of polylactic acid regulation and further etching of polylactic acid?PLA?and tetraethoxysilane?TEOS?hydrolysis.The main content of this paper are showed as follows:?1?In the first part,according to our previous work,the stability of the the fluoro-emulsion only stabilized by surfactant Hypermer-B246 is poor.The porous material prepared by B246 has a large pore size and poor mechanical properties.In here,we selected PLA as a co-stabilizer to improve the stability of the fluoro-HIPE by increasing the viscosity of the continuous phase while decreasing the interfacial tension between oil phase and water.The effects of concentration and molecular weight of PLA on the pore morphology of fluoro-polyHIPEs were thoroughly investigated.Polylactic acid has good compatibility with fluoromonomers.High internal phase emulsions?HIPEs?with excellent stability and the porous PolyHIPE materials with enhanced mechanical properties are prepared.Besides that,this type of porous fluorinated-foams has excellent oleophilicity and hydrophobicity,with water contact angles?WCA?up to 148.4°?nearly superhydrophobic?.Compared with porous materials without adding PLA,the mechanical properties are significantly improved,the compression performance is improved by 275%,and the compressive strength is as high as4.43 MPa,which is superior to many engineering foam materials.?2?In the second section,due to the different properties of fluoro-monomers and non-fluorinated monomers?such as styrene-based monomer?,the traditional surfactants,e.g.Hypermer series?A70?or span series?span-60,span-80,span-85?and tween series?tween-20,tween-60,tween-80?are used alone,were unable to prepare a stable fluoro-emulsion,and it was difficult to obtain a complete porous polymer monolith.In order to solve this problem,we put our eyes on the investigation of composite stabilizers.In this part,we find that polylactic acid?PLA?can be used together with traditional surfactants span-80 to synergistically stabilize the fluoro-HIPE.After polymerization,porous foams with controllable and adjustable pore morphology can be obtained.Firstly,the effects of span-80 or PLA concentration were investigated separately,and it was found that the pore size of porous materials decreased with the increase of PLA content.However,when the content of surfactant span-80 increased,the pore structure of the poyHIPE becomes broken and incomplete.This phenomenon showed the importance of PLA in stabilizing polylactic acid.What's more,multi-stage porous fluoro-material with high specific surface area can be prepared by selectively etching PLA.The number of nano-sized pores and sub-micron-connected pores throat on the pore wall was increased after etching PLA.Several characterizations were applied to indicate removal of PLA such as gravimetric analysis,infrared analysis and thermogravimetric testing.The BET results demonstrated the increase in specific surface area after etching PLA.And the increased specific surface area was positively correlated with the amount of PLA.Oil-water separation experiments show the multi-stage pore polyHIPE had a faster adsorption rate and a higher adsorption capacity.?3?In third section,to overcome some of the limitations of fully organic polyHIPE,hybrid organic-inorganic composite porous polymers are particularly attractive.Here,hybrid fluorosilicon porous polymer SiO₂-Poly?TFEMA/DVB/MPS?was preparated based on hydrolysis and polycondensation of tetraethoxysilane?TEOS?and HIPE template.The effect of the hydrolysis of TEOS on the morphology of polyHIPE under different acid or base environments was studied.The introduction of TEOS increases the mechanical strength and thermal stability of the material.The new fluorosilicone porous materials have low thermal conductivity and can be used in several fields such as thermal insulation materials.