聚苯胺與聚噻吩衍生物/奈米碳材複合材料之合成與電學性質研究

Abstract

本研究合成聚苯胺與聚噻吩衍生物製備導電性奈米碳管複合材料探討其導電性、電磁波屏蔽與其他光電性質。第一部分我們以乳化聚合法合成奈米級聚苯胺粒子，並採用本實驗室自行開發之absorption-transferring process，使之分散於環氧樹脂中。Absorption-transferring process 是以苯胺聚合雙酚A系列之環氧樹脂(DGEBA)為母體，利用其加熱後之黏滯性在水相媒介中吸附懸浮之奈米顆粒。其優點可避免奈米粒子聚集且不需任何有機溶劑。由掃描式電子顯微鏡分析聚苯胺/環氧樹脂材料，可明顯觀察出奈米級聚苯胺顆粒均勻分散在母體中，觀察不到大規模聚集的現象。利用阻抗分析儀量測其介電行為並呈現負介電常數現象，可推斷該材料呈現出巨觀的電荷未定域化現象。使用電磁波屏蔽測試，均勻分散的聚苯胺/環氧樹脂材料在100~1000MHz的電場頻率範圍最高可達到30~60dB的屏蔽效果。在導電薄膜部份，我們合成含壓克力與氫氧官能基之環氧樹脂為光阻劑，經過曝光顯影製程不同線寬圖形，再利用光阻劑表面之氫氧基與2, 4-Toluene diisocyanate(TDI)反應後接上3-Methyl-3,4-dihydro-2H-thieno[3,4-b]dioxepin-3-yl)methanol (ProDOT-OH)單體，再將薄膜浸泡入水中，加入3-thienyl ethoxybutanesulfonate (TEBS)與三甲苯磺酸鐵進行共聚反應，製得導電薄膜。在PET基板上之軟性導電薄膜其圖形解析度(line widths/spaces)為100μm/100μm與10μm/5μm，最佳導電度為90 S/cm，可見光範圍之透明度達70%。而材料之導電性與圖形線寬、聚合時間均有所影響。最後我們亦合成低能隙高分子製備奈米碳管與碳球複合材料討論有機半導體之光電特性。Poly(3,4-dihexyloxythiophene) (PDHOT) and poly(3,4-dimethoxythiophene-co- 3,4-dihexyloxythiophene) [P(DMOT-co-DHOT)] 以紫外光-可見光譜分析儀判定其能隙約為1.34~1.38 eV之間，並以之與官能化奈米碳管混掺，得到分散均勻之奈米碳管/低能隙高分子複合材料。由掃描式電子顯微鏡觀察，當官能化奈米碳管含量高達20wt%，奈米碳管仍均勻分散在母體中觀察不到明顯大規模聚集。此外，我們將PDHOT和P(DMOT-co-DHOT)與奈米碳球(PCBM)混合製備太陽能電池元件，檢測其光電性質。

In this study, we prepared different conducting polymer and carbon nanotube composites including polyaniline nano-particle, polythiophene derivative and MWNT/PANI core-shell material to discuss their conductivity, EMI shielding efficiency and optoelectrical properties. First section, novel polyaniline (PANI)/epoxy hybrids have been fabricated using an absorption-transferring process in which no organic solvent is involved. An epoxy prepolymer cured by aniline monomer (DGEBA-aniline) was added to a freshly prepared PANI nanoparticles (NPs) aqueous solution with vigorous agitation and heating (ca. 90 C). The PANI NPs were absorbed on the surface of epoxy droplet and then transferred into the whole droplet. The microstructures of the product PANI/epoxy hybrids, characterized using scanning electron microscopy, featured well-dispersed PANI NPs (ca. 40□60 nm) within epoxy matrixes; no large aggregates were observed. The hybrids exhibited huge negative permittivities; the electromagnetic interference shielding efficiency in an electric field at low frequency (100-1000 MHz) was ca. 30-60 dB. The well dispersed PANI NPs not only provided a continuous conducting network but also a higher level of charge delocalization. On other hand, we also synthesized MWNT/PANI core-shell (MPCS) structure, it could also dispersed in DGEBA-Ani through absorption-transferring process. In the section of conducting patterned film, A UV-curable photoresist containing hydroxyl groups has been prepared from a mixture of a photoinitiator, epoxy-acrylate resin, hydroxyethylmethacrylate, and tripropylene glycol diacrylate. Patterns having line widths/spaces of 100/100 μm and 10/5 μm were fabricated on a PET (Polyethylene terephthalate) substrate using lithography techniques. 3-Methyl-3,4-dihydro-2H-thieno[3,4-b]dioxepin-3-yl)methanol (ProDOT-OH) was self-synthesis through urethane-linkages onto the surface of the patterned photoresist on the PET film, which was then dipped into a solution of the other monomer, 3-thienyl ethoxybutanesulfonate (TEBS), and initiator and in situ–polymerized to form conductive poly(ProDOT-OH-co-TEBS) films covering the surface of the patterned resist. The optimal conductivity of the poly(ProDOT-OH-co-TEBS) film was ca. 90 S/cm with an optical transparency of ca. 70%. The conductivity of the film was controlled by the polymerization reaction time and the resolution of the pattern. These conductive patterned films might be applicable to the manufacture of industrial touch panels or chemical/biological sensors. Finally, we prepared nanocomposites of multi-wall carbon nanotubes (MWNTs) and low-energy-bandgap conjugated polymers incorporating 3,4-alkoxythiophene monomers. Poly(3,4-dihexyloxythiophene) (PDHOT) and poly(3,4-dimethoxythiophene-co-3,4-dihexyloxythiophene) [P(DMOT-co-DHOT)] have relatively low energy bandgaps (ca. 1.38 and 1.34 eV, respectively), determined from the onsets of absorbances in their UV–Vis spectra, because of the electron donating effects of their alkoxy groups. MWCNTs have poor solubility in common organic solvents; after surface modification with alkyl side chains using the Tour reaction, however, the MWCNT-HA derivatives were readilydispersed in CHCl3 and could be mixed with the low bandgap polymers. Scanning electron microscopy images revealed that MWCNT-HA was dispersed well in each polythiophene derivative; only a few MWCNT-HA bundles could be observed at a high MWCNT-HA content (＞ 20 wt%). The electrical conductivities of the MWCNT/PDHOT composites were dependent on their MWNT contents, reaching 16 S/cm at 30 wt% MWCNT-HA. We suspect that the two hexyloxy chains of PDHOT enhanced its solubility and allowed it to wrap around the surfaces of the MWCNTs more readily.