Study On The Preparation And Properties Of Epoxidized Rubber Crosslinked By Ionic Liquid And Composite Polymer Electrolyte

Ionic liquid?IL?is a molten liquid at room temperature consisting of cations and anions.IL have excellent characteristics such as negligible vapour pressure,non-flammability,non-corrosiveness,high thermal stability,high ionic conductivity and wide electrochemical window,which make them suitable for numerous applications,e.g.as solvents in preparative chemistry and electrolytes in lithium batteries.Functional ionic liquid?FIL?attracts increasing interesting because of the reaction of their functional groups.A novel composite material was prepared by reaction of epoxy group from epoxidized natural rubber?ENR 50?with carboxyl from1-carboxymethyl-3-methylimidazolium bis?trifluoromethylsulfonate?imine?[?HOOC?C₁C₁Im][NTf₂]?.The cross-lingking reaction and cross-linked structure of ENR 50/[?HOOC?C₁C₁Im][NTf₂]were investigated using the Attenuated total reflectance-Fourier transform infrared?ATR-FTIR? spectroscopy,differential scanning calorimetry?DSC?and equilibrium swelling method.The results indicated that the epoxy ring reacted with carboxyl producing hydroxyl and produced ester group at the condition of40°C which caused the glass-transition temperature?T_g?of ENR50/[?HOOC?C₁C₁Im][NTf₂]composite increased by nearly 40°C compared to pure ENR 50.And with increasing content of[?HOOC?C₁C₁Im][NTf₂],T_g shifted down to a lower temperature,and the endotherm peak broadened.DSC and equilibrium swelling method demonstrated that ENR 50/[?HOOC?C₁C₁Im][NTf₂]composite did crosslink.Moreover,non-isothermal DSC method indicated that the reaction order n is close to 1,and the apparent activation energy is 63.79⁷9.28 kJ/mol.ENR 50/[?HOOC?C₁C₁Im][NTf₂]/LiTFSI composite polymer electrolyte?CPE?was prepared through introducing bis?trifluoromethanesulfon?imide lithium salt?LiTFSI?into the ENR50/[?HOOC?C₁C₁Im][NTf₂]composite and the ionic conductivity of the CPE was studied by A.C.Impedance.The results showed that the ionic conductivity increased with the increasing content of both LiTFSI and[?HOOC?C₁C₁Im][NTf₂].Ionic conductivity of samples with[?HOOC?C₁C₁Im][NTf₂]was 2³ orders of magnitude higher than samples without[?HOOC?C₁C₁Im][NTf₂].When added 190 phr LiTFSI and 280 phr[?HOOC?C₁C₁Im][NTf₂],the electrolyte composites reached a maximum ionic conductivity of 3.01×10^-4 S?cm^-1?25°C?in the experimental range.According to the above design concept,the preparation of ENR 50/[BMMIM][NTf₂]composites and ENR 50/[BMMIM][NTf₂]/LiTFSI CPE were successfully synthesized by taking 1-aminopropylimidazolium bis?trifluoromethylsulfonyl?imine ionic liquid?[BMMIM][NTf₂]?instead of[?HOOC?C₁C₁Im][NTf₂],taking advantage of the reaction of carboxyl with amino.The cross-lingking reaction and cross-linked structure of ENR50/[BMMIM][NTf₂]were investigated using ATR-FTIR,DSC and equilibrium swelling method.ATR-FTIR results showed that epoxy ring of ENR 50 and amino of[BMMIM][NTf₂]reacted,producing hydroxyl and imino group at the condition of 40°C which led to the crosslinking of ENR 50/[BMMIM][NTf₂]and an increase of T_g.Non-isothermal DSC method results indicated that the reaction order is close to 1,and the apparent activation energy is 73.03¹18.69 kJ/mol.In addition,A.C.impedance spectroscopy and cyclic voltammetry?CV?were used to study the electrical properties of ENR 50/[BMMIM][NTf₂]/LiTFSI CPE.It was found that when adding 96 phr LiTFSI and 280 phr[BMMIM][NTf₂],the ion conductivity of the system reached a maximum of 2.72×10^-4 S?cm^-1.Meanwhile,CV curves showed the electrochemical window is almost 5.0V.There were four methods to gain epoxidized nitrile rubber?ENBR?by using oxidizing agent to oxidize C=C double bond into epoxy group.FTIR and ¹³C nuclear magnetic resonance spectroscopy(¹³C-NMR)jointly confirmed the occurrence of this reaction and also found that3-chloroperbenzoic acid?mCPBA?has the best effect.Using non-water titration with hydro-bromide/Glacial acetic to test the epoxidation of ENBR,it could be found that the epoxidation degree was about 29 mol%.According to the above design concept,ENBR/[?HOOC?C₁C₁Im][NTf₂]composites and ENBR/[?HOOC?C₁C₁Im][NTf₂]/LiTFSI CPE were successfully prepared.The cross-linking reaction and cross-linked structure of ENBR/[?HOOC?C₁C₁Im][NTf₂]were investigated by FTIR and DSC.The results demonstrated that after epoxidation,T_g of ENBR increased nearly 40°C compared to pure NBR;while adding[?HOOC?C₁C₁Im][NTf₂]could increase T_g of ENBR approximately 51°C.A.C.Impedance showed that when adding 280 phr[?HOOC?C₁C₁Im][NTf₂]and 96 phr LiTFSI,the ionic conductivity of ENBR/[?HOOC?C₁C₁Im][NTf₂]/LiTFSI reached 3.33×10^-5 S?cm^-1.