新型無機/高分子奈米複合材料之合成與性質 (一)異質凝聚法合成TiO2/Poly(AA-co-MMA)奈米粒子及應用PET混摻之研究 (二)高導電PEDOT薄膜及ZnO nanorods/PEDOT薄膜之研究

Synthesis and Properties of Novel Inorganic/Polymer Nanocomposite Part 1 Heterocoagulation of TiO2/Poly(AA-co-MMA) Nanoparticles and Blending with PET Part 2 PEDOT Film with High Conductivity and ZnO Nanorods/PEDOT Composite Thin Film

陳瑞宏(Jui-Hung Chen)

指導教授 ： 戴子安

共同指導教授 ： 邱文英(Wen-Yen Chiu)

國立臺灣大學/工學院/高分子科學與工程學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.00419

摘要

本論文為研究無機/高分子奈米複合材料之合成與性質。第一部分為以異質凝聚法合成TiO2/poly(AA-co-MMA)奈米複合顆粒。首先在水相中以水解-凝縮反應合成TiO2和SiO2/TiO2奈米級粒子，再與poly(AA-co-MMA) 乳膠混成形成複合顆粒，最後與PET粉末進行混煉。複合顆粒的TGA結果顯示，帶負電的乳膠顆粒和TiO2和SiO2/TiO2經由較強的電荷吸引力結合，而帶正電的乳膠顆粒以pH值差異所引起的凝聚、羰基螯合作用及氫鍵三種作用力和TiO2和SiO2/TiO2粒子結合。以無乳化劑乳化聚合所得之poly(AA-co-MMA) 乳膠顆粒，由於其粒徑較大，總表面積較少，因此TiO2的吸附量較少。若以SiO2/TiO2取代TiO2，其吸附量會大幅上升。以SEM觀察PET和複合顆粒的混煉，可發現PET與帶正電的複合顆粒所得之混煉，在型態上比PET與帶負電的複合顆粒所得之混煉較為均勻。DSC的結果顯示，PET和複合顆粒混煉後，玻璃轉移溫度(Tg)和熔點(Tm和Tm’)會上升，結晶溫度的範圍則會縮小。顯示複合顆粒的存在會影響PET結晶時分子鍊的移動和堆積，因此改變PET的熱性質。

第二部份為ZnO nanorod/PEDOT複合薄膜。PEDOT具有高導電度和高透明度的特性，可作為電極和可撓式電子材料。本研究將EDOT單體和具有磺酸根的TEBS單體，起始劑Fe(OTs)3和弱鹼imidazole (IM)溶於甲醇中，再旋轉塗佈於玻璃上，以高溫進行氧化聚合成共聚物薄膜後，其導電度會大幅提升。本研究改變各反應物和EDOT單體的莫耳比例(TEBS/EDOT，IM/EDOT，Fe(OTs)3/EDOT)，並探討其對光電性質，表面型態及導電度的影響。在最佳的組成下，所得共聚物薄膜的導電度可達170 S/cm，較純PEDOT薄膜的30 S/cm高出五倍以上。導電度的提昇源自於TEBS使聚合反應的速度變慢，而使所得的共聚物薄膜均勻度提升。藉由計算反應常數之比例、分子量之比例、及兩種單體在共聚物中的分佈，可更進一步研究聚合動力。計算EDOT和TEBS的反應常數之比例可推知，EDOT較容易被氧化而接到分子鍊上。當TEBS的含量增加時，所得共聚物的分子量會增加，此乃TEBS在共聚物鍊上的含量也相對增加。當IM與EDOT的莫耳數比為2，所得共聚物的分子量為最高。當Fe(OTs)3含量提高時，所得共聚的分子量會降低，共聚物的分子練長也會變短，其原因推論為所得的共聚物分子鍊數目增加。之後在PEDOT上成長ZnO nanorods，以製備ZnO nanorods/PEDOT複合薄膜。製備的步驟分為三個部份：氧化聚合PEDOT薄膜、成長ZnO晶種、以水熱法成長ZnO nanorods。醋酸鋅與氫氧化鈉在甲醇中反應，可製備奈米及ZnO粒子，而此ZnO奈米粒子可作為ZnO成長時的晶種。欲使晶種ZnO nanorods垂直成長於基材上，晶種的存在是非常重要的。HMTA比氫氧化鈉更適合使ZnO nanorods垂直成長於PEDOT薄膜上。藉由控制水熱法的反應條件，可使ZnO nanorods垂直成長在PEDOT薄膜上。此ZnO nanorods/PEDOT複合薄膜具有酸鹼緩衝的能力，且其酸鹼緩衝能力和純ZnO粉末可相比。

關鍵字

二氧化鈦 ； 聚丙烯酸-甲基丙烯酸甲酯 ； 乳化聚合 ； 異質凝聚法 ； 聚三四乙烯基二氧噻吩 ； 氧化鋅 ； 導電高分子 ； 水熱法

並列摘要

In this research, inorganic/polymer nanocomposites were synthesized and studied. The first part was heterocoagulation of TiO2/poly(AA-co-MMA) nanoparticles. Nano-sized TiO2 or SiO2/TiO2 particles were prepared by hydrolysis and condensation reactions in aqueous media, followed by mixing with poly(AA-co-MMA) latex to form different composite particles, then blending with poly(ethylene terephthalate), PET. The TGA results of composites indicated that negative charged latexes had greater interaction with TiO2/ or SiO2/TiO2 particles through strong electrostatic forces, while cationic latexes incorporated with TiO2/ or SiO2/TiO2 particles by pH induced coagulation, carbonyl group chelation and hydrogen bonding. The soapless latex polymer particles showed lower ability of adsorption to TiO2 particles due to the decrease of total surface area of these larger particles. If SiO2/TiO2 particles were used instead of TiO2 particles, unexpected high adsorption result was observed. Morphology results observed by SEM showed that PET blended with positive charged composites was more homogeneous than PET blended with negative charged composites. DSC results also indicated that the Tg of PET was increased, melting temperatures (Tm or Tm’) were increased, and the temperature range of crystallization was narrowed after blending with the composites. The presence of composites affected the mobility and packing of PET molecular chains therefore changing the thermal properties of PET.

The second part was to synthesize highly conductive PEDOT film and ZnO nanorods/PEDOT composite thin film. PEDOT represented a class of conjugated polymers that could be potentially used as an electrode material for flexible organic electronics due to their superior conductivity and transparency. We demonstrated that the conductivity of a PEDOT containing copolymer film could be further enhanced by the oxidative chemical in situ copolymerization of a liquid film spin-coated from monomer mixture 3,4-ethylenedioxythiophene (EDOT) and 3-thienyl ethoxybutanesulfonate (TEBS), oxidant (iron(III) p-toluenesulfonate (Fe(OTs)3), weak base (imidazole, IM), and solvent (methanol). We investigated the effect of the processing parameters such as the molar ratios TEBS/EDOT, IM/EDOT, and Fe(OTs)3/EDOT on the surface morphology, optical property, and the conductivity of the resulting copolymer films. These parameters were optimized to achieve conductivities for the copolymer films as high as 170 S/cm, five times higher than the PEDOT film synthesized with method. This conductivity enhancement for the copolymer films was found to be resulted from the fact that the addition of TEBS monomer reduced the copolymerization rate, leading to the formation of much more uniform film surface without defects which increased the conductivity of the copolymer film. Kinetics study of copolymerization of EDOT/TEBS was conducted by calculation of the reactivity ratio, molecular weight ratio, and monomer distribution in the copolymer. The calculation of reactivity ratio revealed that EDOT was oxidized by oligomer more easily than TEBS. As TEBS/EDOT increased, the molecular weight also increased as a consequence of higher content of TEBS in the copolymer chain. Molecular weight was highest when IM/EDOT equaled 2. Higher content of Fe(OTs)3 resulted in lower molecular weight and shorter copolymer chain due to the increasing number of copolymer chains.

ZnO nanorods/PEDOT film was fabricated by a three-step process: PEDOT polymerization, ZnO seeds annealing, and hydrothermal growth of ZnO nanorods. ZnO nanoparticles were synthesized from reaction of zinc acetate and sodium hydroxide in methanol medium and used as seed for ZnO growth. The presence of ZnO seed layer was important for ZnO rods to grow perpendicularly on substrates. For ZnO rods to grow on PEDOT films, hexamethylenetetramine, HMTA, was preferred as the source of base. By controlling the concentration and condition of hydrothermal growth, ZnO nanorods were able to grow perpendicularly on the PEDOT film. The pH buffering ability of ZnO nanorods/PEDOT film with four hydrothermal growth cycles was comparable to pure ZnO powders.

並列關鍵字

TiO2 ； poly(AA-co-MMA) ； emulsion polymerization ； heterocoagulation ； PEDOT ； ZnO ； conducting polymer ； hydrothermal process

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