The Synthesis And Resistance-switch Performance Of ROMP Block Polymers Containing Carbazole And Naphthalimide-pendants

With the convenience for our daily life brought by the high-tech and high intelligent electronics,such as 5G network,Internet of things,intelligence appliance and automatic drive,there come the problems of producing digital data at a rate we never see before and designing a method to store all this digital bit.The data storage materials we use every day have reached their full potential and to further tap their ability to store more bits is to increase the misreading rate of the aimed device,to enhance the complicity of the produce process and to put up the manufacture cost of each data storage product.So many researchers have turned their eyes to the organic and polymeric resistance switching memory device to deal with the mounting data derived from our daily life.Our research group have focused on the design and synthesis of donor-acceptor containing organic molecule and polymer material since the very beginning of this research field and have made a lot of achievement based on the donor-acceptor system.While the most well-researched organic memory devices are based on the three-layer configuration of metal/organic-film/metal,in which the uniformness and stability of nano-film layer will have a vital influence on the reliability and retention of the resulted memory device.In this thesis,we synthesize the narrow polymer dispersity index block polymer containing carbazole-donor and naphthalimide-acceptor through the ring-open metathesis polymerization(ROMP)technique,after which the amphiphilic block polymer will go through self-assembly to produce nanoscale digital-bit storage unit of the similar size.This way,the problem about the variability in the film thickness and molecule stacking of the conventional three-layer device will be solved.The three parts of this thesis are as follows.(1)The influence of Carbazole-donor and Naphthalimide-acceptor distribution along the polymer backbone on the memory performance:Firstly,we synthesize two different polymers.One(Named CaNa)contains a Carbazole-pendant block and a Naphthalimide-pendant block.The other(Named SiP)is a homopolymer with Carbazole-Naphthalimide coupled pendant.Then we study the influence of deployment of electron donors and acceptors along the polymer backbone on the polymer film stacking and on the resulted device performance.As the test results indicate,the film of CaNa polymer shows flat surface,the sign of phase separation and very little periodic stacking.The film of SiP shows a flat surface and regular stacking because of the π-π interaction between the large pendants.Then the ITO/Polymer/Al memory device performances of the two polymer were characterized.The SiP device has the WORM(Write-Once Read-many times)behavior and a low set/open voltage.This is due to that the regular stacking of the polymer chain will create orderly charge-carrier paths through the film,which will in return lower the voltage drop along the direction perpendicular to the polymer film.While the CaNa device demonstrates the Flash performance and a higher set-voltage,which is related to the higher optical band gap and pendants conformation change in the polymer film.(2)The synthesis and memory-performance characterization of nano-sphere-assembly of three-block polymer with Carbazole-donor pendants block,Naphthalimide-acceptor pendants block and PEG2000 hydrophilic pendants block(D-A-H):Taking advantage of the living-polymerization ROMP technique,we successfully synthesize three-block polymer by controlling the feeding mass and feeding time of different monomers in the polymerization process.After the selective solution of de-ionized water,the amphiphilic polymer will undergo self-assembly and form nano-scale micelles.Afterward,a redox initiating couple,APS and TEMED,of emulsion polymerization will be used to crosslink the micelles in the solution and produce the cross-linked nano-particles.As the polymer dispersity index of this amphiphilic three-block polymer is closed to 1,the nano-assemblies it produced have similar diameter.As the XRD test results indicate,the self-assemble micelles and the cross-linked nano-particles all have a π-π stacking diffraction peak and d-spacing diffraction peak,but the cross-linked particles only show denser molecule-molecule packing and chain stacking.Compared with the spinning coating method in the first chapter,the memory performance reliability of different self-assemble nanoparticles can be improved because of the increasing of polymer-chain stacking regularity in these assembly,the shrinkage of information storage-unit size and the size similarity between different self-assemble particles,through which the self-assembly method is proved worthwhile.(3)Polymeric Nano-square prepared from amphiphilic ROMP polymer micelles by secondary assembly and its memory performance:after the achievement of self-assembly micelles and nanoparticles in chapter 2,we synthesize the amphiphilic polymer SiPEG550 containing hydrophobic block with Carbazole-Naphthalimide coupled pendants and hydrophilic block with PEG550 pendants.Then we study the micelle-forming self-assembly behavior of the amphiphilic polymer in water and the micelle-entity secondary-assembly phenomenon when the micelle solution is coated on flat substrate to dehydrate the solution.Under the influence of the hydrophilic and hydrophobic chain segment interaction,the π-π interaction between the aromatic pendants and the stiffness of the ROMP polymer backbone containing alternative linking units of five-member rings and carbon-carbon double bonds,the dilute amphiphilic SiPEG550 micelles solution can go through secondary self-assembly to produce neat polymeric nano-square units,which maybe is the first polymer nano-square self-assemble entity as far as we know.After discussion about the forming mechanism of those polymeric nano-square self-assembly based on the test results of AFM,TEM and the reported literature,we conduct the current-voltage sweeping on the nano-squares to gain their resistance switching performance.They also demonstrate positive voltage switching behavior.