Synthesis, Characterization And Luminescent Properties Of Alkyl, Alkoxyl Substituted Polythiophenes

3-Bromothiophene and 3,4-dibromothiophene were synthesized in high yield from thiophene,.48% (w/w) aqueous hydrobromic acid, 35% (w/w) aqueous hydrogen peroxide solution, anhydrous liquid ammonia and sodium. In this reaction, the excess aqueous hydrogen bromide was used, the yield of 3,4-dibromothiophene was increased, and the yield of 3-bromothiophene was decreased correspondingly. The yield of product was diminished when excess anhydrous liquid ammonia was used in the rearrangement process.In the presence of (dppp)NiCl2,3-bromothiophene and 3,4-dibromothiophene can react with Grignard reagents to afford 3-isopentylthiophene, 3-pentylthiophene , 3-dodecylthiophene ,3,4- diisopentylthiophene and 3,4-didodecylthiophene in good yields,respectively. 3-methoxythiophene , 3-pentoxythiophene , 3-octoxythiophene, 3-(2-ethyl)hexoxy- thiophene were synthesized from 3-bromothiophene and alcohol using CuI with anhydrous sodium bisulfate as catalysts. The obtained compounds were characterized by 'H NMR, MS and elemental analysis. In the Grignard reaction, when the number of the carbon atom in the alkylbromide is decreased, the reaction rate and the yield of products will be increased. Cul and CuBr show similar catalytic activity in the synthetic process of 3-methoxythiophene. Synthesis of alkoxylatedthiophene monomers is more difficult than that of alkylatedthiophene monomers, and the synthetic technique is more complicated.A number of derivatives of substituted polythiophenes(Pt) such as poly(3-isopentylthiophene)[Piat5], poly(3-pentylthiophene)[Pat5], poly(3-dodecylthiophene) [Pat 12], poly(3,4- didodecylthiophene)[Pat 1212], poly(3,4-diisopentylthiophene) [Pat55],poly (3-octoxylthiophene)[Paot8], poly(3-pentoxylthiophene)[Paot5], poly[3-(dodecy1-co-octoxy1 (thiophene] [CoPt 12-o8] and poly [3 -(dodecyl-co-pentoxy1) thiophene] [CoPtl2- o5] have been synthesized using Fe(III) as catalyst. All polymers exhibit excellent solubility in common organic solvents such as chloroform, dichloromethane, benzene, toluene, THF etc. The chemical structure of each polymer has been characterized by 'H NMR method respectively. All these results indicate that our 3- substituted and 3,4-substituted PT derivatives have well-defined electronic and chemical structures, and straight chain polymers are dominant. In particular, the good solubility of the again consistent with these results. The Molecular weight of each polymer has been determined by gel permeation chromatography (GPC) method respectively, and found that the all polymers have high Molecular weight andAbstractrelatively low polydispersity index.The absorption and emission properties of polymers in chloroform solution and spin-coatting film have been studied. Except for the films of Paot8 and Paot5, in the solution and the solid state , the polymers display different color from red to green photoluminescence. The absorption and emission maximum of Patl212 and Pat55 were blue shifts more than that of Patl2(or Pat5 or Piat5).This behaviour of the poly(3,4-dialkylthiophene) can be easily explained by a non-planar conformation of the polymer backbone resulting from strong steric interaction between the substituents and thiophene rings. The absorption and emission maximums of Copolymers [CoPtl2-o8, CoPtl2-o5] were between the two homopolymers correspond data .And the absorption and emission maximums of Paot8 and Paot5 were more red shifts than that of pat12(or Pat5 or Piat5). These facts were interpreted in terms of strong electro donating effect of the alkoxy groups.The band gaps of piat5, pat5 and pat12 were 2.2 eV, pat1212 were 2.5 eV,pat55 were 2.7 eV, paot5,paot8,pt12-o5 and Ptl2-o8 were 2.1 eV, respectively, these results were estimated from the edge of absorption spectra of spin-coatting films.Single layer polymer LEDs(ITO/Polymer/Al) have been fabricated. It is found that the Pat 12 , Pat5 and Piat5 emit stronger red light, the Paot8 and Paot5 emit weaker red-orange light and the Pat1212 emit weaker yellow light. The emitted wavelengths were 678 nm, 643 nm ,640 nm, 647n...