Fabrication And Performance Study Of Self-healing Polymeric Separation Materials

Due to their good flexibility,plasticity and processability,polymer separation materials are widely used in oil/water separation,gas separation,seawater desalination,organic liquid separation,natural organic matter removal,dye separation,etc.Polymer separation materials inevitably suffer physical or chemical damage during use,resulting in loss of separation performance.Combining self-healing capabilities with polymeric separation materials will effectively increase the service life of polymeric separation materials.With the efforts of a large number of scientific researchers,self-healing polymeric separation materials have made considerable improvements.However,the following problems still exist in the current self-healing separation materials:（1）Most of the self-healing separation materials have harsh healing conditions,which require higher temperatures or other conditions（e.g.UV light,solvents,etc.）to assist in the healing process,and most of the materials cannot perform autonomous healing.How to achieve autonomous healing of separation materials under mild conditions is one of the current research challenges.（2）Existing self-healing oil/water separation materials can only accomplish a single type of damage healing after suffering physical damage（cutting,piercing,etc.）or chemical damage（3）Self-healing ionogel separation materials that can be healed autonomously have poor mechanical properties（<1 MPa）,which limits the use of the materials.In this paper,we aimed to optimize the material selection and molecular design to fabricate self-healing polymeric separation materials with compatible self-healing and separation properties to address the above three problems:1.Superhydrophobic porous materials that can simultaneously heal physical or chemical damage and perform oil/water separation have been fabricated.2.High-strength ionogel-based gas separation membrane with high transparency and autonomous self-healing at room temperature have been fabricated.1.In this work,we fabricated a self-healing hydrophobic polyurea（PDMS-PUa）by step type polymerization of bis（3-aminopropyl）-terminated poly（dimethylsiloxane）（H₂N-PDMS-NH₂）with isophorone diisocyanate（IPDI）.PDMS-PUa can restore the loss of hydrophobicity caused by chemical damage through surface reorganization,using polymer migration to the damaged area and hydrogen bond reconstruction to heal the loss of structural integrity caused by mechanical damage.Subsequently,the self-healing superhydrophobic oil/water separation materials（MCNTs/PDMS-PUa）were fabricated by solution casting method using PDMS-PUa as the skeleton,MCNTs as rigid nanofillers,Na Cl as a pore-former agent.MCNTs provided the micro-nano-structure for MCNTs/PDMS-PUa,conferring excellent superhydrophobicity with a water contact angle of 153±0.7°.The photothermal conversion ability of MCNTs enables them to heal the damage quickly and effectively under sunlight irradiation.When MCNTs/PDMS-PUa were pierced by nails or etched by O2 plasma,the damaged structure and surface wettability result in loss of oil/water separation performance.PDMS-PUa,as a polymer skeleton conferred excellent healing ability to MCNTs/PDMS-PUa.MCNTs/PDMS-PUa porous materials healed the chemical damage through surface reorganization.Meanwhile,the large number of double hydrogen bonds in PDMS-PUa and good chain movement ability of PDMS assist the MCNTs/PDMS-PUa porous material to heal the physical damage,thus realizing the repair of MCNTs/PDMS-PUa oil/water separation performance,and the oil/separation efficiency can still reach 97.9%after healing.2.In the second work,we mixed the tetrahydrofuran（THF）solution of O,O’-bis（2-aminopropyl）poly（propylene glycol）-block-poly（ethylene glycol）-block-p oly（propylene glycol）（H₂N-PPG-PEG-PPG-NH₂）and the 1-ethyl-3-methylimidaz olium bis（trifluoromethanesulfonyl）imide salt ionic liquid（[EMIm]TFSI）with th e THF solution of Benzene-1,3,5-tricarbaldehyde（BTC）.The ionogels with high mechanical strength（stress>1 MPa）,excellent transparent（average transmittanc e 92.28%）and room temperature autonomous self-healing ability were obtained by Schiff reaction of-NH₂ and-CHO.The cross-linked network formed by the bis-amino group of H₂N-PPG-PEG-PPG-NH₂ and the tri-aldehyde group of BT C provided mechanical properties for the ionogel.In addition,the cross-linked network can wrap a large amount of ionic liquid without leaking,thereby ensu ring the stability of the ionogel.The reversible dynamic imine bond formed by the Schiff reaction can complete the exchange and reconstruction at room tem perature,which provides a reliable basis for the room temperature autonomous self-healing of ionogel.The ether-oxygen bond of the block polymer H₂N-PPG-PEG-PPG-NH₂ selected in this work has a high philicity for CO₂.Furthermore,the[EMIm]TFSI has a lower viscosity,and Lewis acid-base interaction of TF SI anion with CO₂ can greatly improve the permeability of CO₂ to I-SPN₉₅/IL_n.Based on the excellent gas permeability and self-healing of ionogel,we prepar ed self-healing ionogel that can be used for gas separation,which can still be achieved after healing even after being pierced by a nail.In the work of this chapter,the self-healing ionogel fabricated with dynamic imine bonds based cro ss-linked network and[EMIm]TFSI has excellent self-healing ability,good mec hanical properties and high transparency,which can be applied to CO₂ gas sep aration.