聚吡咯次甲基共軛高分子之合成及電子結構

含噻吩以及環二氧乙基噻吩所合成的次甲基共軛高分子，由於其所具有的低能隙和可調整的光電性質，而引起科學家們的興趣。然而，以吡咯為主的次甲基共軛高分子至今尚無被深入的研究。這篇論文將討論含吡咯之次甲基共軛高分子和聚環二氧乙基吡咯的理論電子結構、合成方法和其電子組態。　　在理論分析部份，使用高斯套裝軟體計算含吡咯單聚高分子和次甲基高分子的幾何結構與電子組態。聚次甲基吡咯和聚次甲基環二氧乙基吡咯計算出來的電子能隙為0.73和0.68電子伏特，因其主鏈形成醌型結構，所以得到的能隙也較單聚物高分子來的低。由於環二氧乙基的提供電子能力，造成聚次甲基環二氧乙基吡咯具有低於聚次甲基吡咯的游離能和電子親和力。除此之外，計算含有氧、硫、硒、氮之次甲基環二氧乙基高分子以探討雜原子的影響。由於含氮之次甲基環二氧乙基高分子具有以醌型結構為主的幾何結構，使其具有最小的游離能 (2.54 eV) 、電子親和力 (1.86 eV)，以及電子能隙 (0.68eV)。實驗部分，分別以1-甲基吡咯、1-苯基吡咯和環二氧乙基吡咯做為單體，與苯甲醛利用酸催化進行縮合聚合反應，成功合成出不同的聚次甲基吡咯共軛高分子 (PmPy-b)、(PphPy-b, PphPy-nb, PphPy-mb)、(PbEDOP-b, PbEDOP-nb)。從可見光紫外線吸收光譜和電化學實驗可以得到PphPy-b, PphPy-nb, PphPy-mb , PmPy-b的電子能隙為 (1.99, 1.73, 2.01, 1.89) 和 (1.81, 1.83, 1.86, 1.65)電子伏特。而高度脫氫和拉電子的二氧化氮官能基使得PphPy-nb和PmPy-b具有相對於其他兩個高分子的低能隙。另外，PbEDOP-nb具有比其母質聚吡咯 (2.85 eV)、聚環二氧乙基吡咯 (2.0 eV)還要低的能隙 (1.4 eV)，也可由此印證環二氧乙基和二氧化氮取代基對電子能態的影響性。而且，從結果可以推測含吡咯的次甲基共軛高分子為一種新穎的低能隙高分子。

關鍵字

吡咯；次甲基共軛高分子；電子結構

並列摘要

Methine bridged conjugated polythiophene and poly(dioxyethylenethiophene) have attracted significant scientific interest due to intrinsic small bandgaps and tunable optoelectronic properties. However, such class of polymers based on pyrrole has not been explored yet. In this thesis, the theoretical electronic structures, synthesis, and electronic properties of methine bridged pyrrole and poly(ethylenedioxypyrrole) are reported. The theoretical geometries and electronic properties of polypyrrole (PPy), poly-3,4-ethylenedioxypyrrole (PEDOP), poly(pyrrylene methine) (PPy-M) and poly(3,4-ethylenedioxypyrrole methine) (PEDOP-M) were analyzed by Gaussian03 program package. The calculated bandgaps of PPy-M and PEDOP-M are 0.73 and 0.68 eV, which are much smaller than those of the corresponding homopolymers, PPy, and PEDOP, due to the incorporation of quinoid moiety. PEDOP-M shows a smaller HOMO and LUMO values (2.54 and 1.86 eV) than PPy-M (3.20 and 2.47 eV) because of its electron-donating ethylenedioxy moiety. Besides, the electronic properties of four poly(3,4-ethylenedioxyheteroatom methine)s (PEDOX-M, X=O, S, Se, NH) were also analyzed to explore the effects of heteroatom. The theoretical bandgaps are 0.91, 0.93, 0.88, and 0.68 eV for PEDOS-M, PEDOT-M, PEDOF-M, and PEDOP-M, respectively. PEDOP-M has the geometry of quinoid-methine-quinoid-like and results in the smallest IP/EA (2.54/1.86 eV) and lowest bandgap (0.68eV) among the four polymers. Methine bridged conjugated polypyrrole derivative was successfully synthesized from n-methylpyrrole/benzaldehydes (PmPy-b), n-phenzylpyrrole/benzaldehydes (PphPy-b, PphPy-nb, PphPy-mb), and n-benzyl-3,4-ethylenedioxypyrrole/ benzaldehydes (PbEDOP-b, PbEDOP-nb) using acid-catalyzed polymerization. The optical and electrochemical bandgaps of PphPy-b, PphPy-nb, PphPy-mb, and PmPy-b are (1.99, 1.73, 2.01, 1.89) and (1.81, 1.83, 1.86, 1.65) eV, respectively. The small Eg of PphPy-nb and PmPy-b than the other two polymers might be due to higher degree of dehydrogenation or electron-withdrawing nitro side group. The optical bandgap of PEDOP-nb had a relatively small optical bandgap of 1.45 eV, which was much smaller than that of PPy (2.85eV) and PEDOP (2.0eV). It suggests the significance of ethylenedioxy fused ring and nitro side group on the electronic properties. The present study indicates the methine bridged conjugated polymer based on pyrrole derivative are a class of low bandgap polymers.

並列關鍵字

pyrrole ； methine ； conjugated polymer ； electronic properties

參考文獻

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聚吡咯次甲基共軛高分子之合成及電子結構

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