Synthesis And Self-Assembly Of Fluorinated Acrylates Block Copolymers With Topological Structures

Block copolymers with different topological structures can form a series of self-assembly structures due to their thermostability,water and oil repellency and surface properties,and they could be used in many areas such as drug delivery,luminescent material,nanodevice,biosensor.Synthesize and self-assembly of fluoropolymers with different topological structures need further investigation now.At this background,we synthesize amphiphilic block copolymers containing fluoropolymers and poly(ethylene glycol)(PEG),and star-shaped fluorinated acrylates copolymers include polyhedral oligomeric silsesquioxane(POSS)via atom transfer radical polymerization(ATRP).What's more,the self-assembly of the fluorinated acrylates copolymers are investigated through breath figure(BF)and Langmuir-Blodgett(LB)methods.First of all,the PEG macroinitiator with terminal group of bromine is prepared with PEG and 2-Bromopropionyl bromide through substitution reaction.The structure of the PEG macroinitiator is characterized by Fourier Transform Infrared Spectrometer(FTIR)and Nuclear Magnetic Resonance(NMR).Herein,using the PEG macroinitiator as the initiator,the fluorinated acrylate pentablock copolymers of poly(trifluoroethyl methacrylate)-b-poly(methyl methacrylate)-b-poly(ethylene glycol)-b-poly(methyl methacrylate)-b-poly(trifluoroethyl methacrylate)(PTFEMA-b-PMMA-b-PEG-b-PMMA-b-PTFEMA)has been synthesized through ATRP.The structures of the copolymers are characterized by FTIR,NMR and X-ray photoelectron spectroscopy(XPS).Gel permeation chromatography(GPC)is applied to determine the molecular weight and molecular weight distribution of the copolymers,and the polydispersities are in the range of 1.49-1.58.Thermal properties are investigated by thermo gravimetric analyzer(TGA)method,and it is found that the thermal stability enhanced with the increasing content of fluoropolymer chains and hydrophobic chains.It is found that the flat films obtained from the three copolymers had excellent hydrophobic and oleophobic properties,and with the increase of the content of fluoropolymer chains,the hydrophobic and oleophobic properties are increased.The star-shaped fluorinated acrylates copolymers containing POSS are synthesized through ATRP and characterized by FTIR,NMR and XPS.In addition,the fluorine contents of the three star-shaped fluorinated acrylates copolymers are also obtained.Secondly,the three pentablock copolymers used as film-forming materials are prepared to fabricate honeycomb structured porous films through BF method.Several critical influence factors such as macromolecular structures,solvent properties,copolymer concentrations and substrates are investigated to control the morphology of the pores.It is found that the copolymer structures have a great influence on the morphologies of the pores.The three pentablock copolymers can form regular porous films,and the pore sizes of the porous films are increased by enhancing the molecular weigh of the copolymers.The solvent affects the formation of the morphology of the pores.It is found that the chloroform is the best solvent for the formation of the regular pores.In addition,the honeycomb porous films can be prepared in a large concentration range(15-60 mg/m L)through BF method,and an increase in the copolymer concentration leads to a decrease in the pore size.Solid substrates such as silicon wafer,stainless steel and ITO glass could influence the pore structures,which ascribes to the different affinity of water and copolymer solutions with different substrates.With respect to the silicon wafer,the ice substate can form larger pores but the pores are not regularity.When the dimethyl silicone with different viscosity used as the substrate,the pore size is increased with the increasing viscosity.In addition,the porous structures prepared on various liquid substrates are related to the surface tensions and viscosities of the liquid solvents.The pore size is increased by enhancing the viscosity and decreasing the surface tension of the liquid solvents.It is found that with the increase of the content of fluoropolymer chains,the hydrophobic property of the porous and peeled films is increased.Additionally,the peeled films have excellent water-adhesion ability.The water droplet impact behaviour is also explored on the flat,porous and peeled films from liquid substrates.It is found that the rebounding tendency of water droplet becames more and more obvious with the increasing hydrophobic properties.Then,the self-assembly of the pentablock copolymers is investigated at the air-water interface.It is found that the additive amounts,solution concentrations,and copolymer structures can influence the surface pressure isotherms.With the same additive amount and concentration,the two pentablock copolymers with higher molecular weights have four regions: gas,liquid,solid and collapse regions.On the other hand,the copolymer with lowest molecular weigh does not have collapse region.On the same mean molecular area,the surface pressure is higher with the increasing molecular weight.Compare the addition method with compression method,it is found that the the surface pressure in the compression is higher than that of in the addition method.Furthermore,the compression modulus in the compression and addition methods show a trend of decrease after the first increase,and the modulus in the compression method is higher than in the addition method.And then,the relaxations of the copolymers on the three different regions are investigated,and it is found that the relaxation is apparent with the increasing surface pressure,and the relaxation time is higher.The relaxations in the liquid region and solid region are affected by two different kinds of physical processes.A relaxation process is proposed that related to the adsorption–desorption exchange of molecules and polymer segments on the surface(fast relaxation process)and the reconformation of the adsorbed macromolecules inside the adsorption layer(slow relaxation process).However,the first region is affected by only one physical process.It can obtain the dilational modulus from the relaxation isotherms,and it is found that in the same mean molecular area the compression modulus is higher than the dilational modulus.In addition,the LB films prepared at different surface pressures from the three copolymers are scanned by atom force microscopy.Finally,the packing model of the structure evolution for the pentablock copolymer aggregates at the air–water interface is proposed.Finally,the rheology and aggregation behavior of three star-shaped fluorinated acrylates copolymers are investigated at the air-water interface.It is also shown four regions in the surface pressure isotherms,and appeared a pseudoplateau region which is different from the pentablock copolymers.The three copolymers show two peak values in the compression modulus isotherms,which is related to the phase transformation and variation tendency of the surface pressure.In addition,the hysteresis is not happened in the beginning of the compression due to there is no conformation change.On the other hand,the hysteresis is clear in the solid region.Meanwhile,it is found that the relaxation time is larger with the compression.In the end,the surface morphologies of the LB films are scanned by AFM,and the formation mechanism is also proposed.