Preparation And Properties Of Polyphenylene Sulfone With Main Chain Containing Pyrene And Application In Multi-walled Carbon Nanotubes Modification

Polyphenylene sulfone(PPSU)is one of special engineering plastics with excellent performance,which has been widely applied in the fields of aerospace,automotive,new energy and other fields.However,more and more rigorous application conditions demand higher performance of PPSU.Therefore,we can improve the performance of the PPSU through chemical modification or physical modification.For preparing PPSU composite materials,the most common method of physical modification is adding some high performance fillers.This method can improve the comprehensive performance of PPSU,at the same time,it can also reduce the cost of materials.As a result,the application fields of PPSU composite materials have been extended.Multi-walled carbon nanotubes(MWCNTs),as an excellent nanofiller,have attracted attention of many researchers in recent years,and their application fields bave been becoming more and more extensive.However,MWCNTs have a large specific surface area.There are van der Waals forces,?-? stacking,electrostatic and hydrogen bonding interactions between MWCNTs,which make it easy for MWCNTs to agglomerate and difficult to disperse effectively in the resin matrix.And it may limit the performance of MWCNTs in resin matrix composites.To improve the dispersion degree of MWCNTs,we usually use covalent modification or non-covalent modification to modify MWCNTs.At present,many studies have shown that covalent modification can achieve better dispersion of MWCNTs in matrix materials.However,covalent modification would destroy the surface texture of MWCNTs,which will affect the performance of MWCNTs,so that the advantages of MWCNTs can not be fully exploited.Non-covalent modification relies onintermolecular force to modify MWCNTs,and it doesn't cause secondary damage to the surface texture of MWCNTs.From the purpose of protecting MWCNTs surface texture,compared with covalent modification,non-covalent modification is a better choice.As for the method of non-covalent modification,it is common to use small molecule dispersants to modify MWCNTs.However,due to the poor heat resistance during the material processing,the small molecule dispersants would decompose.Obviously,they are not suitable for high-performance polymer system,such as polyarylether sulfone.In addition,polymer modifiers can also be used to disperse MWCNTs.Polymer modifiers are mostly through the chain coiling to disperse MWCNTs.Although the dispersion degree of MWCNTs can be improved to a certain extent with the help of polymer modifiers,the modification effect of polymer modifier is not obvious.Pyrene,containing aromatic ring structure with large ?conjugate system,can disperse MWCNTs through the ?-? stacking interaction with the sidewall of MWCNTs.The non-covalent modification of MWCNTs can be achieved by introducing the pyrene group into the polymer.It can also ensure the interaction between the polymer modifier and MWCNTs and it is suitable for the high-performance polymer system,which demand high processing temperature.Therefore,from the aspect of molecular design,we designed and synthesized a series of polyphenylene sulfone polymers containing pyrene main chain(PPSU-m-Py),which can achieve the modification of MWCNTs.First,pyrene-containing diphenol monomer was synthesized,and then it was copolymerized into the main chain of the polymer to obtain a series of PPSU-m-Py polymers.Test results showed that the polymer modifiers have good heat resistance.The glass transition temperature of the polymer modifiers were above 245 ?,and5% weight loss temperature of the polymer modifiers were above 555 ? in air atmosphere.They are suitable for PPSU and other high performance polymer systems,which demand high processing temperature.Next,we carried out a series of experiments on the dispersion condition of MWCNTs,including the types ofpolymer,ultrasonic time,polymer concentration and polymer molecular weight.The results were as follows: When the concentration of MWCNTs was 2 mg/m L,the concentration of polyphenylene sulfone containing 20% pyrene on main chain(Py-0.2)at 10 mg/m L reached the best dispersion effect on MWCNTS.And the dispersion concentration was as high as 700 mg/L.In addition,we got a series of PPSU/MWCNTs composite materials with different contents of MWCNTs by means of solution blending.The test results showed that,compared to pure PPSU,the mechanical properties and thermal properties of MWCNTs/PPSU composites modified by Py-0.2 were improved.When the amount of MWCNTs was 0.5 wt%,the tensile strength was 5.08 MPa higher than that of pure PPSU,and the Young's modulus was 30% higher than that of pure PPSU.When the amount of MWCNTs was 0.2 wt%,the strain at break was 30% higher than that of pure PPSU.In a word,the MWCNTs modified by Py-0.2 have good dispersibility in PPSU resin,and the composite materials show good potential application prospect.