Control Of Conjugate Polymer Chain Conformation And Aggregation Structure And Effects On Photoelectric Properties

Conjugated polymers are widely concerned in the field of organic optoelectronics and they can be used to prepare high-performance optoelectronic devices.Conjugated polymers have the characteristics of soluble,good film-forming,etc.In the process of preparing the device solution processing method is often used.In addition to the chemical structure of the polymer itself,the photoelectric properties of the conjugated polymer are closely related to the molecular chain conformation and the aggregation structure.Base on the “soft matter” property of polymer,the chain conformation and aggregation of the conjugated polymer were controlled by changing the molecular environment,adding the external stimulus,introducing the pendant group and so on without changing the molecular structure of the polymer.Meanwhile,relationship between chain conformation,aggregation structure and photoelectric properties will be discussed.In the first chapter,there are some review of previous studies,about ways to achieve the control of conjugated polymer chains and the structure of aggregates,and the effects of special chain conformation and aggregation structures on photoelectric properties,with particular emphasis on the effects of chiral structures.The second chapter,conjugated polymer chain conformation and photoelectric properties: the importance of solution pre-organization.For the fluorene-carbazole alternating copolymer m PCF,adjusting the chain conformation and aggregation structure by poor solvent.Chloroform is the good solvent of m PCF,and it can be proved by 1H-NMR spectrum,Raman spectroscopy and theoretical calculation that with the addition of poor solvent methanol in the chloroform solution,the polymer chain conformational conformation is more planar.According to the result of theoretical calculation,the conformation in excited state and charged state are also more planar than ?-phase m PCF in ground state,which mean that the energy used to adjust the conformation by the vibration relaxation will be reduced during the excitation and charge transport of the molecule,sp the energy used for the radiation transition will increase energy will increase and the carrier will be more rapid transmission.The third chapter,conjugated polymer chain conformation and photoelectric properties: effect of chiral side group.Introduce chiral(s)-and racemic 2-methylbutyl groups in fluorene-carbazole copolymers to obtain(s)-m PCF and m PCF,respectively.The GPC,NMR,UV absorption spectra,fluorescence spectra and infrared spectroscopy were used to verify that the two polymers were consistent with the other chemical structures except chirality of the side group.Under the induction of chiral side group,polymer chain of(s)-m PCF become much softer,the molecular size of(s)-m PCF is much smaller the film-forming property is better.In the process of preparing the device,the softer polymer(s)-m PCF can form a more flat,less defective film.And due to the large molecular rigidity of m PCF,the formation of thin film has many holes.As a result,the OLED device performance of(s)-m PCF,such as brightness,luminescent efficient and holes mobility is higher than those of m PCF.The fourth chapter,conjugated polymer chain conformation and photoelectric properties: solvent induced chain entanglement and gel.In this chapter,the photoelectric properties of the conjugated polymer gel was investigated by constructing the gel system of P-PPV.Polymer P-PPV form the gel structure under the influence of limonene.This gel is a physical gel,and while the concentration is 2mg/ml,Limonene/C = 7:3,the gel point is between 40 oC and 50 oC.Gel structure has big effects on polymer chain conformation,solution viscosity,film morphology and spectral properties.As shown in AFM pictures,the diameter of the P-PPV linear aggregates decreased after the added with limonene,the curvature of the chain increases,showing a distinct random coil structure,a relatively straight chain is more curved,increases the probability of chain entanglement,and leads to the formation of aggregated microstructures and gels.The aggregation of microstructures inhibits the movement of the molecular chains and reduces the relaxation of the molecular chains during excitation to the ground state,improving the luminous efficiency and the fluorescence lifetime.The fluorescence efficiency increased from 0.852 to 0.943,and the fluorescence lifetime increased from 0.7ns to 1.28 ns.Limonene plays a key role in the formation of gels.Experiments show that other poor solvents such as methanol can not induce gel formation.We believe that this may be the similarity of limonene with the main chain phenylene vinyl structure so that the limonene solvent is more easily encapsulated in the aggregate of the main chain to form a gel.