Synthesis And Optical Properties Of Polythiophenes Containing Rod - Like Liquid Crystals Unit

With the development of display technology,polythiophene has received more and more attention from researchers as a classical electroluminescent material.In order to improve the molding performance and optical properties of polythiophenes,new liquid crystal polythiophenes with rod-like mesogen was designed and prepared.Using p-bromophenol and 2,5-dibromotoluene as the raw material by Suzuki reaction,the triphenylbenzene derivatives were synthesized as rod-like mesogenic units.And then,3-(((4,4''-bis(decyloxy)-[1,1':4',1''-terphenyl]-2'-yl)methoxy)methyl)-2,5-dibromothiophene(Monomer 1)was prepared by nucleophilic substitution reaction.3-(((4,4''-bis(n-tetradecyloxy)-[1,1':4',1''-terphenyl]-2'-yl)methoxy)methyl)-2,5-dibromothiophene(Monomer 2)was prepared by the same method using n-tetradecyloxy group,instead of decyloxy group;2,5-bis(trimethylstannyl)thiophene(Monomer3)and 2-(trimethylstannyl)-5-(5-(trimethylstannyl)thiophen-2-yl)thiophene(Monomer 4)were prepared with thiophene,2,2'-bithiophene and trimethyl tin chloride as reactants respectively.The homopolymers PTC10 and PTC14 were prepared through Yamamoto coupling reaction of monomer 1 and monomer 2;by the Stille coupling reaction,monomer 1 and monomer 2 were copolymerized with 2,5-bis(trimethyltin)thiophene,5,5'-bis[trimethylsta-nnyl]-2,2'-bithiophene respectively to prepare the corresponding polythiophene copolymers PTTC10,PTTTC10,PTTC14 and PTTTC14.All monomers were characterized by FT-IR and ~1H NMR,etc.The structures and optical properties of the synthesized polymers were characterized by ~1H NMR,POM,UV-Vis,FL and Wide-Angle X-ray diffraction.The molecular weights of the polymers were determined by gel chromatography;the polymers'thermodynamic properties were characterized by differential scanning calorimetry(DSC).In this way,we can obtain the following result:1.The synthesized monomers and polymers with terphenyl mesogen side groups are verified by FT-IR and ~1H NMR to fit the expected structures.GPC show that the synthesized polymers'molecular weight basically exceeded 10,000.It was found all polymers that had been present the liquid crystal state at the corresponding temperature through the DSC and polarizing microscope.X-ray diffraction result shows that they have novel smectic structures.2.The polymer side groups and main chains have absorption peaks respectively in UV-Vis spectrum,and the FL spectrum shows that the synthesized polymers have strong fluorescence in both solution and solid state,and they may apply to good photoelectric materials.3.The relatively ordered structure of liquid crystal state can improve the co-planarity of the main chain,reduce the vibration level of ground state,and narrow the full width at half maxima.4.The fluorescence spectrum show that energy transfer from the mesogen to main chain through a very short flexible spacer can improve the luminescence intensity of the main chain.