Novel fluorescent fluorenyl carbazolyl pyridinyl alternating copolymers synthesis, characterization and properties

Novel Fluorescent Fluorenyl/Carbazolyl-Pyridinyl Alternating Copolymers: Synthesis, Characterization and Properties PAN XIAOYONG (B.Sc., University of Science and Technology of China) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE 2006 Acknowledgements I wish to express my gratitude to my supervisors, Associate Professor Siu-Choon Ng and Professor Hardy S O Chan for their constant guidance and encouragement throughout this project I would like to express my appreciation to Mr Zhou Xuedong, Dr Liu Shouping and Dr Xiao Changyong for their kind assistance in the preparation and characterization of copolymers I would like to express my heartfelt thanks to all graduate students and technologists in our group In particular, I would like to thank Lai Xianghua, Chen Daming, Xia Haibing, Tang Weihua, Liu Xiao and Zhang Sheng, for their advice and friendship I would also like to thank the staff of Central Instrumental Lab, Thermal Analysis Lab, Honours Lab and Chemical Store for their help to obtain spectra, special chemicals and to use the computers Finally, I would like to express my gratitude to the National University of Singapore for the award of a research scholarship and for providing me with the opportunity and the facilities to carry out the research work reported in this thesis i Table of Contents Acknowledgements i Table of Contents ii Summary vi Chapter Introduction 1.1 General introduction to conjugated polymers 1.2 Conductivity in conjugated polymers 1.2.1 Conducting mechanism 1.3 Photoluminescence (PL) in conjugated polymers 1.4 Electroluminescence in conjugated polymers 1.4.1 PLED devices 1.4.2 Light generation in PLED 1.4.3 Quantum efficiency of PLED 1.5 1.6 Application 10 1.5.1 Organic electroluminescent (EL) devices 10 1.5.2 Organic photovoltaic devices 12 1.5.3 Electrochromic devices 14 Aim of the project 15 References 17 ii Chapter Experimental Details 20 2.1 Materials 20 2.2 Characterization Techniques 20 2.2.1 Nuclear Magnetic Resonance (NMR) 20 2.2.2 Gel Permeation Chromatography (GPC) 21 2.2.3 Thermogravimetric Analysis (TGA) 21 2.2.4 Differential Scanning Calorimetry (DSC) 22 2.2.5 Cyclic Voltammetry (CV) 23 2.2.6 Ultraviolet-Visible Spectroscopy (UV-Vis) 23 2.2.7 Photoluminescence Spectroscopy (PL) 24 References 25 Chapter Synthesis and Properties of Poly(fluorenyl-alt-pyridinyl)-Based Alternating Copolymers for Light-Emitting Diodes 26 3.1 Introduction 27 3.2 Experimental Part 29 3.3 3.2.1 Materials 29 3.2.2 Measurements 29 3.2.3 Synthesis 30 Result and Discussion 33 iii 3.4 3.3.1 Synthesis and Characterization 33 3.3.2 Optical Properties 35 3.3.3 Electrochemical Properties 40 Conclusion 43 References 44 Chapter Dendronized Fluorenyl-Pyridinyl-Based Alternating Copolymers: Synthesis and Characterization 48 4.1 Introduction 49 4.2 Experimental Part 50 4.3 4.4 4.2.1 Materials 50 4.2.2 Measurements 51 4.2.3 Synthesis 52 Result and Discussion 57 4.3.1 Synthesis and Characterization 57 4.3.2 Optical Properties 59 4.3.3 Electrochemical Properties 63 Conclusion 65 References 67 iv Chapter Novel Fluorescent Carbazolyl-Pyridinyl Alternating Copolymers: Synthesis, Characterization and Properties 5.1 Introduction 5.2 5.3 5.4 Experimental Part 70 71 73 5.2.1 Materials 73 5.2.2 Measurements 73 5.2.3 Synthesis 74 Result and Discussion 80 5.3.1 Synthesis and Characterization 80 5.3.2 Optical Properties 82 5.3.3 Electrochemical Properties 87 Conclusion 90 References 91 Appendix NMR spectrums of intermediate compounds, monomers and polymers 94 v Summary A few series of novel, soluble fluorescent alternating polymers were designed and synthesized They were poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)-alt-(pyridinyl)] &poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)](I), poly[2,7-(9,9-bis[3,5-bis(benzyloxy)benzyl])fluorenyl-alt-(pyridinyl)](II) and poly[(2,7-(N-(2-ethylhexyl)carbazloyl)-alt-(pyridinyl)] (III) All polymers were prepared by Suzuki cross-coupling reaction and the structures of all polymers were confirmed by 1H-NMR Their properties such as absorption and emission, thermal stability, electrochemical properties were studied The result shows that the different linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases Meta-linkage(3,5-and 2,6-linkage) of pyridinyl units in the polymer backbone is more favourable to polymer for pure blue emission and prevention of aggregation of polymer chain than para-linkage(2,5-linkage) of the pyridinyl units These polymers with pyridinyl units possess very low LUMO energy levels for an easy electron injection from a cathode It also shows that the electronic and optical properties of fluorescent polymers can be well tuned by properly rationalized design of polymer architectures such as the introduction of proper side chain and incorporation of different pyridinyl moieties into polymer backbone vi Chapter Introduction 1.1 General introduction to conjugated polymers Conjugated polymers have been increasingly attracting interest for the past 50 years Earlier conventional insulating-polymer systems were used as substitutes for structural materials such as wood, ceramics and metals because of their high strength, light weight, ease of chemical modification/customization, and processibility at low temperature It was in 1977 that Shirakawa, MacDiarmid, Heeger and coworkers first discovered that the films of polyacetylene (PA) exhibited profound increase in electrical conductivity when exposed to iodine vapor This discovery opened the modern era of conjugated conducting polymers Since then, this class of conducting polymers has been greatly enlarged Many conjugated conducting polymers including polyaniline (PAN) , polypyrool (PPyR) 3, polythiophene (PT) 4, poly(p-phenylene) (PPP) 5, poly(p-phenylene sulphide) 6, and poly(p-phenylene vinylene) (PPV) have been synthesized and studied The electrical conductivities of these polymer systems range from those 104 S/cm (nearly that of a good metal such as copper, 5×10 S/cm) Apart form syntheses and investigation of potential application of new conjugated materials, a prime focus of the field has been the determination of the mechanisms of charge transfer in these organic semiconductors Compared to metals and traditional semiconductors, the conducting mechanism of conjugated polymers is obviously different Metals are intrinsically conducting due to the presence of free electrons In traditional three-dimentional semiconductors, the fourfold (or sixfold, etc.) coordination of each atom to its neighbor through covalent bonds leads to a rigid structure In such systems, the electronic excitation can be usually considered in the context of this rigid structure leading to the conventional concepts of electrons and holes as the dominant excitations However, the essential structural characteristic of conjugated polymers is their conjugated π system extending over a number of recurrent monomeric units The twofold coordination makes these systems generally more susceptible to structural distortion This characteristic feature results in low-dimentional materials with a high anisotropy in conductivity, which is higher along the chain direction As a result, the dominant “electronic” excitations are inherently coupled to chain distortions The terms, solitons, polarons and bipolarons from solid-state physics are used to interpret the excitations in this class of one-dimentional polymer semiconductors When an electron moves in an ionic crystal, its surrounding medium will be polarized with negative ions being repelled away and positive ions being attracted towards it The relative motion of the opposite ions gives rise to a polarization field, which in turn, affects the motion of the electron itself This complex―moving electron and its accompanying polarization field is called a polaron In conducting polymers, the term polaron is used to denote a localized electron state with accompanying lattice distortion, which forms a cation-radical pair Because polarons represent localized distortions of the lattice, the associated energy levels must split off from the conduction and valence band A polaron has a spin state of 1/2 (paramagnetic) In the case of perisitent attractive interaction between two polarons, formation of a stable bound state called a bipolaron is favored Bipolaron is double charged but spinless Similarly, because the structural deformation associated with the two charges is stronger than in the case of a polaron, the electronic energy levels of the bipolarons appear further away form the band edges A charge soliton which is a spinless cation is formed when bipolarons dissociate However, the conjugated polymers are well-known insulators in their pure forms Poly (p-phenylenevinylene) has an intrinsic resistivity of 1016Ω cm7 In order to achieve (semi)conducting materials, charge carriers have to be introduced in some ways Normally, three ways of introducing charge carriers are used: 1) Doping-induced charge carriers 2) Photo- and radiation-induced charge carriers 3) Charge injection from suitable electrodes 1.2 Conductivity in conjugated polymers Similar to semiconductors, the conductivity (σ) of conjugated polymers can be expressed by the following equation: σ=neµ (1.1) Where e is the elementary charge, n is the number of mobile charge carriers and µ is the mobility of the charge carriers The number and mobility of the charge carriers are the two key factors contributing to the conductivity of polymers The first (n) is related to the doping levels while the later (µ) is governed by the transport processes of charge carriers 1.2.1 Conducting mechanism There are two general classes of conducting polymer structures that lead to qualitatively different electronic properties: (i) Systems in which the ground state is twofold 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 2.8 2.4 1.6 0.8474 0.8207 0.7979 0.7712 0.7471 0.7163 0.6922 0.6722 0.5049 0.4849 0.4809 2.0 1.3638 1.2448 1.5498 9.2 2.0140 1.9967 7.8297 7.7936 7.7682 7.7133 7.6892 9.6 1.2 0.8 0.4 0.0 (ppm) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10.2434 13.9552 27.7626 27.0982 24.7441 22.6210 34.5652 33.4242 43.9242 54.6552 83.4687 119.1715 133.3832 130.3358 143.8832 150.1081 (2) 2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(2-ethylhexyl)fluorene 10 (ppm) (2) 2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-bis(2-ethylhexyl)fluorene 95 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 0.8756 0.7297 0.7150 0.6120 0.5986 2.2054 2.1693 8.2554 7.9316 7.9049 7.7898 7.7671 9.5 2.0 1.5 1.0 0.5 0.0 (ppm) 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.6294 0.6066 0.5933 0.8943 0.8782 2.1479 7.7109 7.9263 7.8995 8.1925 8.9056 (3) Poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)-alt-(2,6-pyridinyl)](PDEHFP-26) 0.5 0.0 (ppm) (4) Poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)-alt-(3,5-pyridinyl)] (PDEHFP-35) 96 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 0.6428 0.6227 0.5892 0.5625 0.8836 1.5994 2.1492 8.1578 8.0400 7.9049 7.8768 7.7096 7.6654 9.0622 9.5 1.0 0.5 0.0 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.6842 0.6280 0.6066 0.9398 1.5391 2.1251 7.2613 7.8326 7.8058 7.6587 7.6279 (5) Poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)-alt-(2,5-pyridinyl)] (PDEHFP-25) 0.8 0.4 0.0 (ppm) (6) Poly[2,7-(9,9-bis(2-ethylhexyl)fluorenyl)] (PDEHF) 97 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 3.9139 5.0806 6.8225 7.4540 7.4286 7.4018 7.3764 7.3643 7.3416 7.3202 7.2573 9.6 4.8 4.4 4.0 3.6 3.2 2.8 2.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 1.2 0.8 0.4 0.0 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 2.0 1.6689 1.6502 1.5525 2.1011 4.6417 4.6230 5.0418 6.6339 6.6258 6.5616 6.5536 6.5456 7.4339 7.4125 7.4072 7.3831 7.3764 7.3630 7.3563 7.3510 7.3443 7.3215 7.2573 (7) Methyl α-resorcylate dibenzyl ether 1.6 (ppm) (8) 3,5-Dibenzyloxybenzyl alcohol ([G-1]-OH ) 98 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 2.1707 4.4143 5.0324 6.6486 6.6406 6.5603 6.5536 7.4326 7.4099 7.4072 7.3871 7.3791 7.3671 7.3604 7.3564 7.3483 7.3403 7.3269 7.2600 9.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 1.5445 3.2343 4.7381 5.9355 5.9288 6.3007 7.5838 7.5798 7.4059 7.3831 7.3791 7.3577 7.3390 7.3176 7.3015 7.2828 7.2600 7.2560 (9) 3,5-Dibenzyloxybenzyl Bromide ([G-1]-Br 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 (ppm) (10) 9,9-Bis[3,5-bis(benzyloxy)benzyl]-2,7-dibromofluorene 99 160 140 100 90 80 70 60 45.2402 57.0549 69.7795 110 77.3334 76.9146 76.4957 120 130 101.3384 138.8912 138.1113 136.8980 130.3552 128.4197 128.0298 127.7409 127.2498 150 109.1378 170 121.3569 120.4470 180 150.4026 158.8375 190 50 40 30 20 10 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2756 1.5445 3.4069 4.5695 6.1803 6.1736 6.1656 5.9007 5.8940 8.0360 7.7577 7.7323 7.4607 7.4353 7.3148 7.3082 7.2961 7.2787 7.2653 7.2573 (10) 9,9-Bis[3,5-bis(benzyloxy)benzyl]-2,7-dibromofluorene 1.2 0.8 0.4 0.0 (ppm) (11)2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-Bis[3,5-bis(benzyloxy)benz yl]fluorene 100 160 150 140 130 120 110 100 90 80 70 60 50 24.7281 45.4089 57.0780 69.6425 77.3256 76.9068 76.4736 83.6512 101.0682 109.0113 119.6983 143.9319 138.9783 137.0142 133.8947 130.6597 128.2624 127.6125 127.3525 127.3092 148.0623 158.4460 170 40 30 20 10 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 1.5418 3.4162 4.5748 4.5334 6.0987 6.0479 6.2780 7.2587 7.1744 7.1061 7.7109 7.6868 7.6627 8.2407 8.2233 8.1938 (11)2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-Bis[3,5-bis(benzyloxy)benz yl]fluorene 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 (ppm) (12)Poly[2,7-(9,9-bis[3,5-bis(benzyloxy)benzyl])fluorenyl-alt-(2,6-pyridinyl)] 101 8.4 8.0 7.6 6.8 6.0 5.6 5.2 4.8 3.3440 3.2918 6.4 4.6806 4.6391 7.2601 7.1771 7.2 6.0426 6.0225 5.9784 8.8 6.3570 6.3235 9.2 8.0334 7.6427 7.6146 7.6026 7.5290 7.5036 8.9097 9.6 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 1.3505 1.3371 1.3104 1.2836 1.2608 1.2154 0.8836 0.8622 0.7404 3.3426 3.2958 3.2503 3.1820 4.6778 4.6537 4.6336 4.5948 4.5708 6.2404 6.2217 6.2043 6.0317 5.9929 5.9581 5.9514 5.9113 5.9046 7.2933 7.2719 7.2585 7.2291 7.1916 8.8051 (13) Poly[2,7-(9,9-bis[3,5-bis(benzyloxy)benzyl])fluorenyl-alt-(3,5-pyridinyl)] 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 (ppm) (14) Poly[2,7-(9,9-bis[3,5-bis(benzyloxy)benzyl])fluorenyl-alt-(2,5-pyridinyl)] 102 210 200 190 180 170 160 150 140 6.0 130 5.5 120 31.2602 31.0002 30.7547 30.4947 30.2347 29.9748 29.7148 6.5 116.0395 7.0 121.2966 7.5 124.8929 8.0 133.7897 132.4032 8.5 144.4196 140.9389 138.5702 9.0 150.2978 149.4890 206.7836 9.5 5.0 (ppm) 4.5 110 100 4.0 90 3.5 80 3.0 70 2.5 60 2.0 50 1.5 40 1.0 30 0.5 20 10 0.0 (15) 4,4’-Dinitro-2-azidobiphenyl (ppm) (15) 4,4’-Dinitro-2-azidobiphenyl 103 1.5445 7.6587 7.6279 7.5476 7.5195 7.2600 8.3464 8.3169 8.1631 8.1564 8.1203 8.1122 8.0922 8.0841 210 200 190 180 170 160 150 140 130 120 110 31.2609 31.0009 30.7553 30.4954 30.2354 29.9754 29.7154 7.0 109.2825 116.3163 8.0 123.6534 9.0 127.9286 10.0 142.6317 148.8133 206.7880 11.0 6.0 (ppm) 5.0 100 90 4.0 80 70 3.0 60 2.0 50 40 1.0 30 20 0.0 (16) 2,7-Dinitrocarbazole (ppm) 10 (16) 2,7-Dinitrocarbazole 104 2.0596 2.0529 2.0449 2.8222 8.5631 8.5564 8.5163 8.4869 8.1778 8.1711 8.1497 8.1417 11.3473 210 200 190 180 170 7.0 160 6.5 150 140 6.0 130 5.5 120 5.0 4.5 110 100 31.2746 31.0147 30.7547 30.4947 30.2492 29.9892 29.7292 7.5 97.0472 8.0 109.3380 8.5 120.3867 117.2238 9.0 143.1919 147.2215 206.8125 9.5 (ppm) 4.0 90 3.5 80 3.0 70 2.5 60 2.0 50 1.5 40 1.0 30 0.5 20 10 0.0 (17) 2,7-Diaminocarbazole (ppm) (17) 2,7-Diaminocarbazole 105 2.0502 2.7941 4.4263 6.6312 6.6285 6.6245 6.6218 6.4867 6.4800 6.4586 6.4519 7.5396 7.5115 9.4247 145 140 135 130 125 120 115 110 105 100 95 90 85 80 4.5 75 70 4.0 65 3.5 60 55 3.0 50 2.5 45 2.0 40 35 1.5 30 1.0 25 20 15 10.7782 5.0 13.9269 5.5 24.2106 22.9251 6.0 30.6379 28.3847 6.5 39.0295 7.0 47.4356 7.5 77.3334 76.9146 76.4957 8.0 90.6502 8.5 118.1649 9.0 121.6313 128.0731 141.6210 9.5 (ppm) 0.5 0.0 (18) N-(2-ethylhexyl)-2,7-diiodocarbazole (ppm) 10 (18) N-(2-ethylhexyl)-2,7-diiodocarbazole 106 1.3719 1.3612 1.3465 1.3412 1.3198 1.2997 1.2917 1.2769 1.2555 0.9411 0.9170 0.9077 0.8916 0.8849 0.8595 1.5352 2.0275 2.0074 1.9860 4.0665 4.0558 4.0424 4.0304 7.2587 7.7885 7.7618 7.7096 7.7056 7.5357 7.5317 7.5089 7.5036 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 0.9277 0.9130 0.9037 0.8903 0.8796 0.8675 1.5485 1.3933 2.1318 2.1118 4.2859 4.2618 4.2363 7.2587 7.8781 7.6788 7.6533 8.1256 8.0989 9.5 1.0 0.5 0.0 (ppm) 190 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10.8789 14.0130 24.8452 24.3108 22.9387 30.5645 28.3981 39.1003 47.0438 83.6421 115.5319 119.8214 124.9053 124.6164 140.8213 (19) 2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-N-(2-ethylhexyl)carbazole 10 (ppm) (19) 2,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-N-(2-ethylhexyl)carbazole 107 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.3211 1.3010 1.0535 1.0348 1.0107 0.8903 0.8662 0.8421 0.8314 1.5365 1.4950 2.2763 4.4170 8.3197 8.2849 8.2581 8.1551 8.1323 7.8768 7.8581 9.5 1.5 1.0 0.5 0.0 (ppm) 9.6 9.2 8.8 8.4 8.0 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.9826 0.9692 0.8796 0.8582 0.8408 0.8194 1.5579 1.4616 1.4415 1.2997 2.1974 4.3327 7.7069 7.6199 7.6173 7.5932 7.5731 8.3103 8.2956 8.2688 8.2474 9.0033 (20) Poly[(2,7-(N-(2-ethylhexyl)carbazolyl)-alt-(2,6-pyridinyl)] 0.8 0.4 0.0 (ppm) (21) Poly[(2,7-(N-(2-ethylhexyl)carbazolyl)-alt-(3,5-pyridinyl)] 108 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 (ppm) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 (22) Poly[(2,7-(N-(2-ethylhexyl)carbazolyl)-alt-(2,5-pyridinyl)] 109 0.9665 0.8970 1.5405 1.4361 1.3050 2.2148 4.3407 7.2774 7.2440 9.1211 8.8133 8.7799 8.2287 8.2086 8.1337 7.9464 7.9169 7.8500 7.8220 7.8005 7.7671 7.7377 7.6748 7.5664 [...]... 1996 5 J F Rusling and S.L Suib, Adv Mater., 1994, 6, 922 6 D A Skoog and J J Leary, Principles of Instrumental Analysis, 4th edition, Saunders College Publishing, 1992 25 Chapter 3 Synthesis and Properties of Poly (fluorenyl- alt -pyridinyl) -Based Alternating Copolymers for Light-Emitting Diodes A novel series of well defined alternating poly[2,7-(9,9-di(2-ethylhexyl )fluorenyl) -alt -pyridinyl] (PDEHFP)... copolymers of fluorene unit and pyridine units are expected to possess low HOMO and LUMO energy levels and will achieve a relatively balanced charge injection As an extension of our research work concerning polymeric blue light emitting diodes, 17a-e in the present work, we present the synthesis and characterization of a novel series of blue-emissive alternating copolymers of 9,9-bis(2-ethylhexyl )fluorenyl. .. electron withdrawing pyridinyl units on electrical and optical properties of polymers; 3) Developing short wavelength emission, e.g blue, ultraviolet polymers 4) Preliminarily probing the potential applications of the derived polymers A few series of novel, soluble fluorescent alternating polymers were designed and synthesized They were poly[2,7-(9,9-bis(2-ethylhexyl )fluorenyl) -alt- (pyridinyl) ] &poly[2,7-(9,9-bis(2-ethylhexyl )fluorenyl) ](I),... Silverstein, G C Bassler and T C Morrill, 5th edition, John Wiley and Sons, Inc., 1991, Chapter 4 2 Nicholas P Cheremisinoff, Polymer Characterization Laboratory Techniques and Analysis, Noyes Publications, 1996 3 D Campbell and J R White, Polymer Characterization, Physical Techniques, Chapman and Hall, 1989 4 N P Cheremisinoff, Polymer Characterization Laboratory Techniques and Analysis, Noyes Publications,... &poly[2,7-(9,9-bis(2-ethylhexyl )fluorenyl) ](I), poly[2,7-(9,9-bis[3,5-bis(benzyloxy)benzyl] )fluorenyl- alt- (pyridinyl) ] (II) and poly[(2,7-(N-(2-ethylhexyl)carbazloyl)-alt- (pyridinyl) ] (III) 15 All polymers were prepared by Suzuki cross-coupling reaction The structures of all polymers were confirmed by 1H-NMR Their properties such as absorption and emission, thermal stability, electrochemical properties were studied... linkage position of pyridinyl unit in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film phases Meta-linkage (3,5- and 2,6-linkage) of pyridinyl units in the polymer backbone is more favourable to polymer for pure blue emission and prevention of aggregation of polymer chain than para-linkage(2,5-linkage) of the pyridinyl units CV... in this Chapter, specific electronic and optical properties can be obtained by molecular design through modification of polymer side substitutes or backbones Alternating copolymers are especially interesting in fabrications of LED Given impetus by this, the attention of this project is focused on: 1) Designing and synthesizing novel, processible, highly fluorescent alternating polymers; 2) Investigating... chloroform(AR) and all other reagents were purchased from commercial sources and used without further purification The solvents, diethyl ether and THF were AR and acetonitrile(HPLC) were dried and distillated prior to use 3.2.2 Measurements 1H NMR and 13 C NMR spectra were recorded on a Bruker ACF 300 FT-NMR spectrometer operating at 300 MHz Deuterated chloroform was used as the solvent and tetramethylsilane... sufficient efficiencies and lifetimes to be of commercial value Polymers with large band gaps that emit blue light efficiently have been the subject of intense academic and industrial research and stable blue PLEDs based on conjugated polymers remains a challenge This arises because it is hard to achieve a balanced charge injection due to the large band gap between the LUMO and HOMO energy levels.6... yields In this series of alternating polymers, 2,7-(9,9-di(2-ethylhexyl )fluorenyl was used as light-emitting unit and the electron deficient pyridinyl unit was introduced to tune the wavelength of the emitting light and improve their electron transportation These polymers were characterized by 1H NMR, thermal analysis, Gel permeation chromatography, UV-vis, fluorescence spectroscopy and cyclic voltammetry ... and Characterization 57 4.3.2 Optical Properties 59 4.3.3 Electrochemical Properties 63 Conclusion 65 References 67 iv Chapter Novel Fluorescent Carbazolyl-Pyridinyl Alternating Copolymers: Synthesis,. .. Designing and synthesizing novel, processible, highly fluorescent alternating polymers; 2) Investigating the influence of electron withdrawing pyridinyl units on electrical and optical properties. .. [Eonset]ox and [Eonset]red are the onset potentials for the oxidation and reduction of the polymers, the HOMO and LUMO of the polymers were estimated to be -5.95, -6.23 and -5.43eV and -3.32, -3.62 and