| As a kind of polymer materials with clear application prospects,conjugated polymers have been fully studied and rapidly developed in recent years.However,due to the lack of methods and means for studying conjugated polymer solutions,few researchers have focused on the chain behavior in conjugated polymer solutions.Also,because it is difficult to observe and study,the dynamic evolution process of the conjugated polymer precursor solution to the film is also less studied.This also provides opportunities and challenges for our research work.The study of the relationship between the chain behavior of conjugated polymers and the condensed state of their films is very important.To clarify the chain behavior of conjugated polymer in precursor solution and the condensed structure in film state will be of great significance to the entire conjugated polymer in the preparation of devices and practical applications.This work mainly studies the chain behavior of several conjugated polymer's precursor solution state and the condensed structure in prepared film,as well as the relationship between both.The specific material system is based on the development trajectory of conjugated polymers.We selected the classic copolymerized conjugated polymer F8BT(Poly(9,9-dioctylfluorene-cobenzothiadiazole)),the hydrogen-bonded supramolecular conjugated polymer PPFOH(poly(9-(4-(octyloxy)phenyl)-2,7-fluoren-9-ol))and the classic conjugated polymer blend system F8BT/P3HT(Poly(9,9-dioctylfluorene-co-benzothiadiazole)/Poly(3-hexylthiophene-2,5-diyl))for research.Through the systematic characterization of the three material systems of F8 BT,PPFOH,and F8BT/P3 HT,the chain behavior in precursor solution and the influence of the condensed state structure in film are studied respectively,and the solvent field is used through research methods such as scaling law.The electric field and other external stimuli regulate the condensed matter structure of the chain.This article will be divided into the following sections:Firstly,wit help of the scale law obtained from light scattering and rheological tests,combined with spectroscopy,transmission electron microscopy and morphology research methods,our focus is on the chain behavior of conjugated polymers in solution state(chain shape,size,chain aggregate shape and aggregation density,intrachain/inter-chain interaction,etc.)and its intrinsic physical relationship with the condensed structure of the film and the dynamic evolution of the molecular chain motion mode in solution.The solvation effect of the solution and the concentration change in the solution have been investigated to find the influence of chain behavior and film condensed structure.This section found that the fractal dimension gradually increased when the toluene solution of the semi-rigid conjugated polymer F8 BT was added with different ratios of ethanol;and when the proportion of ethanol was 0%,5%,and 10%,the aggregates were in a one-dimensional rod-like aggregation form.The compactness of the chain aggregates was low.However,when the ethanol content reached 15% and 20%,the compactness of the chain aggregates increased significantly,and its morphology expanded from a two-dimensional lamellar structure to a threedimensional structure.Here,the reason for the gradual increase in the density of chain aggregates was explored,and the influence of solvation on the chain behavior of semirigid conjugated polymer solution and its intrinsic physical relationship with the condensed structure of the film were revealed.According to the concentrationdependent rheological scale relationship,it is also found that the toluene solvent of F8 BT was the ? solvent at room temperature;and the molecular chain motion in the concentration range of dilute solution and sub-concentrated solution is attributed to Zimm and Rouse respectively.The movement mode of the model and further reveals the intrinsic physical relationship and law between the solution and the film.At the same time,it was also found that the critical concentration of F8 BT dilute solution and sub-concentrated non-entangled solution was 7.9 mg/m L.The results of this research are of great importance to enrich the understanding of the solution behavior of semirigid conjugated polymer chains,construct the structure-activity relationship between them and the performance of optoelectronic devices,and further guide the study of the condensed state structure of other types of conjugated polymers in solutions and films.The research will also promote the effective application of the scaling law,a simple and effective method for studying the nonlinear change law of polymer chains,not only in soft material systems such as polymers,but also in other broader research systems with nonlinear properties.Both have important theoretical and practical significance.Secondly,we focused on a special polyfluorene conjugated polymer named PPFOH,with hydrogen bonding supramolecular conjugated polymers in which intermolecular hydrogen bonds could be formed with different solvents,to explore effect of solvents on PPFOH solution state and films condensed state structure in the dynamic evolution process from solution to film.It was found that chain aggregation size,shape and aggregated density presented obvious difference in PPFOH solution with different solvents.Chain aggregation size was obviously increased in PPFOH chloroform(CF)/tetrahydrofuran(THF)mixed solution with different THF ratios.A stretched and rigid chain conformation with dense chain aggregation was presented in pure CF solvent and there was a small number of fine lattice fringes with spacing0.229 nm and irregular crystalline appearance with the CF solvent.Although ordered structures region was increased in the aggregation of PPFOH CF/THF mixed solution with 20% THF,the direction was cluttered with increased lattice fringe spacing of0.252 nm.However,a large-area and long-range ordered chain aggregation was presented in PPFOH mixed solution with 100%THFsolvent with lattice fringes spacing0.596 nm and chains aggregation orderness was quite high,the lattice fringe direction was high consistent.Interchain interaction between PPFOH chains or between PPFOH chains and solvents molecules(CF or THF)led to the difference of chain aggregate state structure of PPFOH solution state.More importantly,it was found that there was heredity of the chain condensed state structure from solution to films in CF solvent in the dynamic evolution process due to strong intermolecular hydrogen bonds interaction between PPFOH molecules in solution state and film.However,influence of solvents on film condensed state structure was limited because of solvent evaporation in the filming process,thus leading to interchain-interactions enhancement between PPFOH chains in all solvents.However,the condensed state structure of the final film was mainly decided by interactions of PPFOH chain itself but no solvents.Therefore,a rule of deciding chain aggregated state structure heredity from solution to film was revealed,that is,whether the intermolecular force both in solution and film are the same.If the intermolecular force between PPFOH are the same,the chain aggregated state structure from solution to film are of heredity;if they are different,the aggregated state structure from solution to film aren't of the heredity.The research indicates intermolecular hydrogen bonds plays an important role to decide effect of solvents to solution state till film,It is significant not only to reveal effect of solvent on conjugated polymer solution behavior and film condensed state structure but also to deeply understand the physics essence of condensed state structure formation in the dynamic evolution process from solution to film in order to well control conjugated polymer condensed state structure to achieve photoelectric devices with high efficiency and stability.In the third part,we use the external electric field method to control the solution chain behavior of the blended conjugated polymer system(F8BT/P3HT),and explore the influence of the precursor solution on the condensed structure of the prepared film.First find the best electric field strength to achieve the best control effect.The conjugated polymers blended in different proportions have different responses to the electric field.Compared with the single-stranded and smaller aggregation signals in the solution before the electric field is applied,large-scale aggregations appear in the solution after the electric field is applied.Subsequently,the emission spectrum test proved that the application of an electric field enhanced the interaction of molecular chains and the degree of order of the polymer chains was also improved to a certain extent.The interaction of conjugated polymer precursor solution after the application of an external electric field was similar to the film that was made in the precursor solution,and a certain spectral shift was also seen in emission spectrum,which can also indicate the chain behavior can directly affect the condensed structure in the film state.This study uses the external field to control the condensed structure of the blended conjugated polymer,and clarifies the mechanism of the response of different conjugated polymers to the external field under the blending system,which will affect the condensed structure of other conjugated polymer blending systems in the future.This research work systematically studied the influence of the chain behavior of several types of conjugated polymers in the solution state and the condensed state structure of their films.We started from the perspective of polymer solution research and essentially studied the conjugated polymers from solution state to film the dynamic evolution process of the state clarifies the change mechanism in this process.This research is not only conducive to the study of the chain behavior of other conjugated polymers in the solution state and the condensed state structure of thin films,but also is of great significance for other conjugated polymers to control the condensed state structure to improve the actual performance of their optoelectronic devices. |
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