| Shape Memory Polymer?SMP?is a new kind of intelligent material,which can be temporarily fixed and restored to its original state under external stimulation such as heat,light,electricity and magnetism.In recent years,SMP has been widely concerned by researchers because of its good shape memory performance and durability.It has been applied in many fields such as aviation,military industry,medicine and so on.For example,polyurethane with good biocompatibility can be used as a shape memory polymer in medical stents,heat resistant,lightweight,high strength polyimide materials are used in space exploration and smart engines.Poly?aryl ether ketone?is a kind of common special engineering material,which has been studied for more than 50 years.It has excellent chemical stability,thermal stability,high mechanical properties and good processability,the poly?aryl ether ketone?has been widely used in the fields of industrial manufacture,anticorrosive coating and seawater desalination film.In addition,poly?aryl ether ketone?as a crystalline polymer has a clear glass transition temperature?Tg?,which meets the basic requirements for thermal to shape memory polymer?TSMP?.However,due to the high Tg of poly?aryl ether Ketone?,its response temperature?Tt?can not be reached at normal temperature.Therefore the application of poly?aryl ether ketone?to TSMP is relatively less studied.In this background,a novel difluoro Monomer DAFD with flexible alkyl structure was synthesized by molecular design and introduced into polymer by nucleophilic substitution polycondensation,a novel poly?aryl ether Ketone?with flexible segment structure in the main chain was prepared.Due to the existence of flexible segment structure in the polymer molecule,the Tg of the new poly?aryl ether Ketone?is obviously lower than that of the traditional poly?aryl ether ketone?,so it has lower Tt and is more suitable to be used as TSMP material.At the same time,different side chain structures were introduced into the new poly?aryl ether ketone?by changing the monomer structure and post-chemical modification,the effects of hydrogen bonding,ionic cross-linking point and covalent cross-linking network on the shape memory properties,thermal properties and mechanical properties were investigated.According to the distribution of the hard and soft segments in the molecular structure,the shape memory properties of SMP materials will be directly affected.Firstly,by adjusting the proportion of the flexible alkyl difluoro monomer DAFD in the copolymerization process,three novel poly?aryl ether ketone?s containing 20%,30% and 40% carboxylic acids were prepared.The results show that the three polymers have high molecular weight and good thermal stability,which meet the requirements of thermally induced SMP.In addition,with the increase of the content of the flexible segment in the main chain of the novel poly?aryl ether Ketone?,its rigidity decreases and the mobility of the segment increases.Therefore,the mechanical strength,toughness,glass transition temperature and energy storage modulus of the polymer decrease.Furthermore,the hydrogen bonding between the carboxyl groups at the end of the side chain of the novel poly?aryl ether Ketone?can form a physical cross-linking point and form a stationary phase with the glassy state of the material,which endows the material with the ability of shape memory.The three polymers all showed good shape fixation?Rf?,and the Rf was over 98%.However,the shape recovery?Rr?of the two poly aryl ether ketone PAEK-40 DFAD with a main chain flexible monomer content of 40% has the best shape recovery?Rr=85.4%?.When the temperature of the new poly?aryl ether ketone?reaches Tt,the deformation energy stored in its stationary phase can drive the shape recovery of the material better.Next,PAEK-40 DFAD novel poly?aryl ether Ketone?with the best shape recovery rate was selected as the polymer substrate,and the carboxylic acids on the side chains of PAEK-40 DFAD were replaced by Sodium carboxylate and calcium carboxylate by salt solution displacement method.The interaction between-COO-at the end of the polymer side chain and Na + or Ca 2 + introduced the ionic cross-linking point into the novel poly?aryl ether Ketone?shape memory materials.The experimental results show that the glass transition temperature of the two kinds of shape memory poly?aryl ether ketone?,Na-PAEK-40 DFAD and Ca-PAEK-40 DFAD,is about 60? higher than that of the original PAEK-40 DFAD.The existence of Ionic cross-linking points significantly improved the shape memory ability of the materials,and both ionic shape memory polymers achieved 100% shape recovery rate,and the time needed for shape recovery was shorter.In addition,Ca-PAEK-40 DAFD exhibited better shape memory performance and better deformation-recovery repeatability due to the interaction between Ca2+ and-COO-salt bridge.The shape memory properties of poly?aryl ether ketone?s were improved by the introduction of ionic bond instead of intermolecular hydrogen bond.In view of the obvious improvement of shape memory property of the novel poly?aryl ether Ketone?by introducing Ionic cross-linking points into the molecular structure,the covalent cross-linking structure was introduced into the polymer by chemical modification,to investigate the effect on the shape memory properties of novel poly?aryl ether ketone?S.Firstly,the side-chain carboxylic acid of polymer was chemically modified by DCC/DMAP system to graft 2-aminanthracene onto the side-chain of polymer,a series of poly?aryl ether ketone?s with different anthracene structure were prepared.A novel poly?aryl ether Ketone?membrane containing covalent crosslinking network was prepared by irradiating the prepared polymer film with ultraviolet light.The experimental results show that the mechanical properties,storage modulus and glass transition temperature of c-PAEK-40DFAD-x are improved by the introduction of covalent cross-linking structure.In addition,the free volume and the mobility of the chain of poly?aryl ether ketone?grafted with anthracene ring increase,so the material has higher deformation under the same conditions.The covalent cross-linking network generated by the anthracyclines on the polymer side chain improves the memory of the initial shape of the stationary phase and stores more elastic deformation energy,furthermore,the shape fixation and shape recovery of cPAEK-40DFAD-x were significantly higher than that of the original Paek-40 dfad. When the grafting rate of 2-aminanthrene was 20%,c-PAEK-40DFAD-20 An showed the best shape memory performance?shape fixation rate: 98%,shape recovery rate: 100%?.Therefore,the shape memory properties of the novel poly?aryl ether Ketone?s can be effectively improved by introducing covalent cross-linking networks. |
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