Design And Research Of Self-assembly Driven By Evaporation Based On P3HT Solution

In recent years,with the development of flexible electronics,conductive polymers have been widely concerned by researchers because of their low manufacturing cost,simple manufacturing process and large-area preparation of flexible devices.They are also used in optoelectronics,biosensors and solar energy conversion.The preparation of polymer semiconductors usually requires solution processing.So far,researchers have proposed a variety of methods to prepare ordered polymer molecules.Generally,self-assembly is the most commonly used method,and the operation is simple.Self assembly is the use of non covalent interaction between molecules,mainly divided into electrostatic interaction,?-?stacking interaction,van der Waals interaction and hydrophobic interaction.Preparation of polymer semiconductors usually requires solution processing.Polymer molecules evaporate in solution to drive self-assembly and then deposit the required patterns.Solution processing is mainly solvent evaporation method,specifically divided into droplet pinning method,spin coating method and other solution processing methods.In this paper,the droplet pinning method is improved,and a microfluidic control system is designed based on the technology of meniscus assisted evaporation.By limiting the polymer solution between two nearly parallel substrates,a meniscus is formed between the two substrates due to capillary action,and the solvent at the edge of the meniscus will evaporate rapidly,resulting in the solution flow between the substrates to the meniscus,which is used to compensate for the solution loss caused by solvent evaporation,and drive the solute transport,and then form self-assembly deposition.The main research work of this paper is as follows(1)Effect of substrate moving rate on self assembly pattern of conjugated polymersPoly(3-hexylthiophene)polymer(P3HT)was used as semiconductor material,and chloroform(CHCl₃)was used as organic solvent.On the premise of pinning the solution to the substrate,the CHCl₃ solution of P3HT is pulled out by the lower substrate at a specific rate and forms a meniscus with the upper substrate due to capillary action.These polymer molecules drive the transport of the solution through marginal solvent evaporation,and self-assembly deposition is carried out near the meniscus due to?-?stacking,forming a regular and orderly structure It is found that the larger the moving rate of the substrate is,the narrower the deposition pattern is.This is due to the smaller volume of the solution compensated by solvent evaporation,resulting in less solute content transported and narrower the deposition pattern.(2)Effect of polymer solution concentration on deposition morphologyCHCl₃ solution with different concentration gradient was selected to prepare P3HT.The substrate moving rate suitable for observation was selected to coat the solution.The formation of deposition pattern and influencing factors of polymer solution during coating were analyzed.The results show that the self-assembly results are related to the concentration of the solution when the substrate moving rate is fixed.The higher the concentration of the solution is,the wider the pattern width is.This is because in the same volume of compensation solution,the higher the concentration of the solution is,the more the solute content is,resulting in the wider the pattern of self-assembly deposition.The same conclusion is obtained by replacing the substrate and repeating the above experiment.(3)Self assembly of polymer solution on noble metal nanoparticlesThe silver particles are evaporated on the substrate,and the polymer solution is patterned on the substrate of pre evaporated silver particles to form ordered linear deposits.The results show that the pre evaporated silver particles have no effect on the morphology of the polymer.The effect of concentration gradient on the morphology of linear deposits is consistent with that of non evaporated silver particles,and the change of substrate morphology has no obvious effect on the assembly of polymer.