Study On Design, Synthesis, Self-assembly And Optoelectronic Properties Of Novel Conjugated Polymers

In this paper, we use the method of introducing the rigid rodPoly(phenylisocyanide) derivatives with stable helical structure into the activechain end of Polythiophene derivatives, through this kind of method, We havesuccessfully constructed two novel "rod-rod" conjugated copolymers, theself-assembly morphology of these polymers in different solvents and thecontrollability of photoelectric properties have also been researched. The mainresearch results are as follows:1. The second chapter of this thesis use a single pot, with Ni(dppp)Cl2forcatalytic initiator, by introducing rigid rod through hydrogen bondingPoly(phenylisocyanide) derivatives (PPI) with stable helix structure in the endof active chain of poly (3-hexylthiophene)(P3HT) with the continuous feedingmethod. We have successfully synthesized a series of molecular weight andcomposition controlled and representative of the poly(3-hexylthiophene) andPoly(phenylisocyanide) derivatives copolymer (P3HT-b-PPI), IR and NMR wereused to characterize the structure of copolymers. Gel permeationchromatography (GPC) was used to detect the molecular weight andpolydispersity of homopolymers and the corresponding copolymers, through thiskind of method, we find that all of polymers are presenting monodispersity.We used the method of differential scanning calorimetry (DSC) to test thecopolymer and found that the copolymer shows two glass transition temperature(Tg) and two melting transition temperature (Tm), and presented a good phaseseparation. Thermogravimetric analysis showed that the copolymer didn’tappear weightlessness phenomenon until at320oC and had good thermalstability. The copolymer was dissolved in tetrahydrofuran, UV-vis detectionfound that the copolymer of larger molecular weight appeared π-π accumulationin the560nm and605nm, Transmission electron microscopy (TEM) and atomicforce microscope (AFM) were used to observe that the copolymers wereself-assembled into spherical nano-micelles with poly (3-hexylthiophene) fornuclear and poly(phenylisocyanide) derivatives for shell. Dynamic lightscattering (DLS) was used to characterlize the size of the sphericalnano-micelles and we found that all copolymers are presenting monodispersity. At the same time, The copolymer was dissolved in chloroform and UV-visdetected the copolymer show no π-π accumulation, transmission electronmicroscope observed the copolymer that it formed amorphous state, but atomicforce microscope showed the copolymer self-assemble into nanometer fiber,through polarizing microscope (POM) observing, the copolymer shows goodsmectic liquid crystal properties.2. In view of researching self-assembly of P3HT-b-PPI, particularly, themorphology of self-assembled in chloroform, we applied the copolymer inorganic field-effect transistor (OTFT) and organic photovoltaic (OPV) devicesin the third chapter, and Preliminary researched its photoelectric performance.Researching shows that copolymer’s hole mobility was7.1×10-4cm2V-1s-1and switch current ratio was1.8×102, Solar energy conversion rate up to0.95%.3. Based on the study of completely hydrophobic copolymer, in the fourthchapter of the thesis, Introduce hydrophilic group into thiophene side chain anduse Ni(dppp)Cl2as catalytic initiator, we synthetized three kind of hydrophilicpolythiophenes [P3(TEG)T] with different molecular weigh through Grignardmetathesis polymerization (GRIM). IR and NMR were used to characterize theirstructure. With the gel permeation chromatography (GPC) test on the molecularweight and polydispersity, the polymer are all presenting monodispersity. UsingUV-vis to detect the polymer found that the polymer appeared red shiftphenomenon with the increased methanol in tetrahydrofuran and methanolsolution of different volume ratio. The polymer also appeared red shiftphenomenon in methanol relative to tetrahydrofuran through fluorescencetesting. Through transmission electron microscope observation, we can foundthat polymer gathered into a smaller nanosphere in tetrahydrofuran and a largernanosphere in methanol.4. Based on the fluorescence properties of the hydrophilic polythiophene[P3(TEG)T], in the fifth chapter of the thesis, introducing rigid rod throughhydrogen bonding poly(phenylisocyanide) derivatives (PPI) which has the stablespiral structure into the active end of hydrophilic polythiophene [P3(TEG)T].We synthesized a series of different molecular weights and compositionsamphiphilic copolymer [P3(TEGT)T-b-PPI] through a pot of method and with Ni(dppp) Cl2as catalytic initiator. IR and NMR were used to characterize the structure. Gel permeation chromatography (GPC) was used to test the molecularweight and dpolydispersity of homopolymer and the corresponding copolymer,there is a phenomenon that all polymer are presenting monodispersity. UV-visdetected that the absorption spectrum of the copolymer appeared red shiftphenomenon with methanol to add in gradually in tetrahydrofuran and differentvolume ratios of methanol solvent, at the same time, new peak at450nm and400nm appeared, the absorption value weakened gradually with the increase ofthe volume of methanol, this due to the π-π interaction of hydrophilicpolythiophene section, the accumulation of the main chain of thiophene wasgradually embedded by hydrophilic side chain with methanol to add. The studyfound that the self-assembly morphology and fluorescence properties of thiscopolymer depend on solvent. The self-assembly morphology of copolymertransform from single stranded fibrous to spherical micelle with PPI for nuclearand P3(TEGT)T for shell. And the size of spherical micelle reduced gradually,while the color of fluorescence spectrum transform from yellow to blue and thechange is reversible. In particular, the copolymer self-assemble into hollowspherical micelle in tetrahydrofuran and methanol mixed solvent whose volumeratio is3:2, In addition, the copolymer can emit nearly white light under the UVlight irradiation with wavelength of365nm.