類別:

黏土插層/脫層機制之策略性研究與黏土/磷難燃性奈米複合材料之應用

2021-06-16T07:09:08Z

標題: 黏土插層/脫層機制之策略性研究與黏土/磷難燃性奈米複合材料之應用; Intercalation Strategies of Synthesizing Clay/Polymer Hybrids and Clay/Phosphazene Nanocomposites for Fire-Retarding and the Synergistic Effect 作者: Jau-Yu Chiou; 邱昭諭摘要: 本論文探討黏土插層/脫層機制形成“黏土/高分子混成材料”之策略性研究與黏土含磷之難燃性衍生奈米複合材料與應用，研究內容主要分敘如下。黏土插層/脫層機制形成黏土/高分子混成材料之策略性研究，係藉由聚醚胺(polyoxyalkylene-amines) 插層劑之親/疏水性質與末端基差異性，探討對層狀黏土有機化改質機制之影響。研究中發現在相同分子量之線性疏水鏈段聚醚胺 (polyoxypropylene-amines, POP-amines)，一端末端基為甲基之 POP-M-amines，與雙端皆為胺基之 POP-D-amines 相比具有最大層間距擴張。由動態實驗發現，POP-M-amines進行黏土插層具有特殊之第二步插層現象，有別於一般插層劑經離子交換進入黏土層間(第一步插層)所觀察到有機量關鍵性插層 (critical intercalation)；第二步插層，黏土之層間距與插層劑量成正比。此階段式插層現象，除了可達到天然黏土脫層型態外，進一步地，可利用此特殊插層機制，將有機化黏土做為奈米容器，把材料儲存於黏土層間之奈米空間，如原油吸附與回收、藥物釋放及相變化 (PCM) 材料 (如paraffin wax) 之包覆等。高分子/黏土 (Polymer layered silicate, PLS) 奈米複合材具有優秀的機械性質、熱穩定性質與生物相容性質。關鍵技術在於親水性之黏土與疏水性高分子間之相容性。本研究，黏土含磷之難燃性衍生奈米複合材料與應用，係以合成 Phosphazene-poly(oxypropylene)-amines (HCP-D400) 為始，並依三種改質方式製得 HCP-D400/NSP、HCP-D400/MMT及HCP-D400/Na+-MMT 有機化黏土，並具有 lower critical aggregate temperature (LCAT) 之特殊性質。經由SEM-EDX、XRD 及 TEM 分析，發現 HCP-D400 與脫層之奈米矽片(NSP) 以物理摻混方式製備之 HCP-D400/NSP 於環氧樹酯中分散效果最佳。更進一步分析複合材料之熱穩定性，當添加 10wt% HCP-D400/NSP 於環氧樹酯，T¬¬10wt% 由 350 oC 增加至 447 oC，T¬¬10wt% 由 500 oC 增加至757 oC ，有效提升環氧樹酯熱裂解溫度 127 oC (T10wt%)與 257 oC (T¬¬80wt%)。限氧指數 (limit oxygen index, LOI) 則提升 7% 至 27%。研究中發現HCP-D400不僅可使奈米矽片均勻分散於環氧樹酯中，進一步的與奈米矽片產生協同作用 (synergistic effect)，提升高分子材料之熱穩定性質。; Layered silicate clays are natural crystallites and are well recognized for their organic intercalation for nanocomposite applications. In this study, a new mechanism is revealed by selection of hydrophobic polyetheramines with a poly(oxypropylene) (POP) backbone and a methyl terminus as the intercalation agent. Specifically, the monoamine with a molecular weight of 2000 g/mol widened the basal spacing of the layered sodium montmorillonite up to 74 A and further expansion to 84 A, 96 A, and 100 A by a second intercalation different from the ionic exchange reaction. Kinetic studies indicated that the first stage of intercalation occurred after a critical concentration of a monoamine, while the second stage had no critical concentration behavior. This two-step method shows the potentials for synthesizing suitable organoclay nanostructures for encapsulating phase change materials (PCM) and oil recovery from the spilt ocean. The exploration of the in-depth understanding of clay confinement chemistry leads the strategic design of new materials and oil recovery process. We further synthesized the phosphazene-amine adduct of hexachlorocyclophosphazene (HCP) and poly(oxypropylene)-diamines of 400 g/mol molecular weight (D400) by amine/chloride substitution and triethylamine removal of HCl. Subsequently, the adduct HCP-D400 was physically mixed with exfoliated silicate platelets (SP) to prepare the HCP-D400/silicate hybrids (HCP-D400/SP). The HCP-D400/MMT (HCP-D400 intercalated Na+-MMT) and HCP-D400/Na+-MMT (HCP-D400 physically mixed with Na+-MMT) were also prepared for comparison with HCP-D400/SP. A more homogeneous silicate distribution HCP-D400/SP than the HCP-D400/MMT counterparts in epoxy nanocomposites was revealed by SEM-EDX, XRD, and TEM analyses. The epoxy nanocomposite with 10 wt% of HCP-D400/SP, HCP-D400/MMT, and HCP-D400 had a degradation temperature at 80 % weight loss (T80 wt%) of 757 oC, 712 oC, and 519 oC, respectively, in comparison with the 500 oC of the pristine epoxy system. Anti-flame test confirmed that the HCP-D400/SP epoxy nanocomposite had a higher limit oxygen index (LOI) of 27.0 % than the HCP-D400/MMT counterpart (24.0 %). The degree of exfoliating the layered clay into random silicate platelets is the predominant factor for the thermal stability enhancement. It is also demonstrated that the co-presence of phosphazene-amines and silicate platelets has a synergistic effect in improving the thermal behavior of the nanocomposites.

黏土之溶膠-凝膠反應與複合材料應用

2021-06-16T02:49:55Z

標題: 黏土之溶膠-凝膠反應與複合材料應用; Clay Sol-Gel Reaction for Molecular Composite 作者: Jenny Jauhari; 仇寶雁摘要: Nanosilicate platelets (NSP) 是由層狀蒙托土 (Na+-MMT) 脫層而得。利用 sol-gel反應將 3-aminopropyltriethoxysilane (APTES) 與NSP邊緣 ≡Si—OH連接形成共價鍵之NSP-amine。另外，NSP-amine 與 Glycidyl methacrylate (GMA) 可藉由開環反應得 NSP-acrylate。定性分析方面利用 29Si 固態核磁共振光譜儀確定 APTES 接上 NSP。NSP-amine 及 NSP-acrylate 定量分析（接枝量和接枝率）由熱重分析儀 (TGA) 分析計算而得。進一步將 NSP、NSP-amine 和 NSP-acrylate 導入紫外線固化系統進行光交聯成膜。亦可將 NSP 和 NSP-amine 導入環氧樹脂藉由熱交聯硬化成膜。並以鉛筆硬度測試硬度差異。利用紫外線固化技術，導入0.5 及 1.0 wt% NSP-acrylate，硬度從4H（未添加黏土）提升至7H及8H。於環氧樹脂系統中，導入0.5 至5wt% NSP-amine，膜之硬度從HB（未添加黏土）提升至 2H、3H 和 4H。另外，未改質之 NSP 導入丙烯樹脂，膜之硬度提升至 6H。而 NSP/環氧樹脂膜提升至 2H。; Nanoscale silicate platelets (NSP) were previously prepared from the newly developed exfoliation of sodium silicate clays (Na+-MMT) by ionic exchange reaction. We further designed the molecular composites by covalently functionalized NSP through its edged ≡Si—OH groups with 3-aminopropyltriethoxysilane (APTES) for amine-functionalized NSP. The consecutive reaction allowed the conversion of NSP-amines to NSP-acrylates through the reaction with Glycidyl methacrylate (GMA). NSP-amine was structurally characterized by 29Si solid-state NMR and thermogravimetric analysis (TGA), while NSP-acrylate only by thermogravimetric analysis (TGA). The NSP-acrylate was applied to the UV-cured resins through the acrylate polymerization in forming molecular composites exhibiting an highly enhanced hardness up to 6H and 8H from the pristine 4H (without clay) by 0.5 and 1.0 wt% NSP loadings, respectively. In epoxies, the NSP-amines promoted the hardness from HB to 2H, 3H, and 4H depending on the NSP loadings from 0.5% to 5% by weight. By comparison, the nanocomposites of dispersing NSP without the covalent bonding amine or acrylate functionalities only achieve the property of hardness in moderate degree, such as 6H and 3H for UV and epoxy systems, respectively. The significances of the silicate platelets in covalently bonding with organic polymer matrices as the molecular composites was realized by comparing with the analogous nanocomposites.

黏土、奈米碳管及奈米銀粒子之混成材料及其導電性探討

2021-06-15T07:08:04Z

標題: 黏土、奈米碳管及奈米銀粒子之混成材料及其導電性探討; Synthesis of Nanohybrids Involving Silicate Clays, Carbon Nanotubes and Silver Nanoparticles, and their Conductivity Studies 作者: Rui-Xuan Dong; 董睿軒摘要: 製造具自我排列特性的奈米材料，其分散技術為製程中之關鍵。於此，我們利用離子交換反應以及非共價鍵方式製造奈米混摻材料，如：將奈米銀粒子修飾在矽酸鹽黏土與奈米碳管上。這篇論文將分成三部份，分別探討奈米材料之分散性、粒徑大小、粒徑分佈及其電性探討。第一部分此部分是探討利用無機矽酸鹽黏土噹分散劑，可合成窄小尺寸分佈及具低熔點之奈米銀粒子。由於天然黏土是片狀幾何形狀，可提供其高表面積固定奈米銀粒子，使其尺寸維持在粒徑大小17−88 nm的範圍。當銀離子/黏土的離子交換當量比為1/1時，可透過掃描式電子顯微鏡及可見光吸收觀察生成之銀粒子具窄小分佈的尺寸(polydispersity of Dw/Dn = 1.2 at 26 nm)及波長為420nm時，有一特徵吸收峰。在無有機分散劑存在下，膠狀之黏土仍可和銀離子嵌合並穩定生成之銀粒子。由於那層間距離僅微小的擴張 (12.0 A versus 13.9 A)，銀粒子是穩定生成在黏土之表面。在經過80 的乾燥並再分散回水中後，銀粒子仍穩定且例子大小均一；更進一步藉由掃描式電子顯微鏡觀察得知，那黏土表面上之奈米銀粒子具有一低熔點 (110)性質。這類銀奈米粒子在低溫下製造銀導線及導管是有其潛在之應用性。第二部分經由將銀離子溶於DMF/water溶劑中，並以poly(oxyethylene)-imide (POE-imide)當為分散劑可將銀粒子修飾於碳管表面，而此高分子(POE-imide)可使碳管及銀粒子不會聚集於溶液之中並可將銀離子還原為銀粒子。由此法製備而成的奈米銀粒子其粒徑分佈為8−30nm並且經由TEM觀察可看到有部分的銀粒子會貼附於碳管表面之上。若無此高分子幫助穩定及還原銀離子，硝酸銀藉由DMF還原過程中，產生銀鏡現象且附著在反應容器之壁上。可以利用紫外光/可見光光譜儀於波長為550nm及420nm分別觀察碳管及奈米銀粒子的特徵吸收峰變化情形。經由水洗將分散劑與自由奈米銀粒子去除後可得奈米銀粒子(20-30nm)之單一多壁奈米碳管。從未經修飾之多壁奈米碳管，此有機分散劑的合成提供了簡單的方法來製備Ag/MWNT奈米混掺材料。第三部分我們呈現一種直接合成poly(oxyethylene)-imide (POE-imide)複合奈米銀粒子/多壁奈米碳管方式，並利用加熱方法探討其混成薄膜之電性。藉由簡單塗層Ag/MWNT/POE-imide混合液於聚醯亞胺基材上並加熱至160 oC，奈米銀粒子遷移至表面且聚集成直徑為100−150 nm，當溫度增加至170 oC時，那複合薄膜外觀轉變成呈現乳白色，其片電阻值也大幅降低為2.2 x 10-1 Ohm/sq，當溫度持續加熱至350 oC時，此時複合膜顯示為白色之表面且具有最佳之片電阻值(2.7 x 10-2 Ohm/sq)。電性之提升是由於奈米銀粒子催化高分子降解並進而熔融，此機制可由掃描式電子顯微鏡(FE-SEM)、熱重分析儀(TGA)及廣角X-ray繞射(WAXRD)等儀器鑑定得知。就我們所知，於此低溫度下所測量之Ag/MWNT薄膜片電阻值是最低的且目前文獻上沒有報導。; “Dispersion technology” is considered as the key step in Bottom-Up process, for self-assemblies and fabricating nanomaterial devices. Herein, nanohybrid materials, including silver nanoparticles decorated on the silicate clay and carbon nanotube, were fabricated by ionic excharge reaction and non-covalent method. These materials were investigated on dispersing ability, particle size and distribution, and electrical behavior. The thesis is divided into three parts: Part 1. Silver nanoparticles (AgNPs) of narrow size distribution and low melting point were synthesized from the reduction of silver nitrate in the presence of inorganic silicate clays. The natural clays with a lamellar geometric shape provided a high surface area for immobilizing AgNPs with nanometer diameter in the range of 17-88 nm. At a 1/1 equivalent ratio of Ag+ to clay counter ions, the generated particles had a narrow size distribution (polydispersity of Dw/Dn = 1.2 at 26 nm Dn by SEM) and a UV absorption at 420 cm-1. Without organic dispersants, the colloidal clays could complex with Ag+ in the initial stage of mixing and subsequently stabilized the generated Ag0 particles. It seems that the high surface area stabilizes the clay rather than the Ag metal intercalation into the layered structure since the basal spacing was only slightly enlarged (12.0 A versus 13.9 A by XRD). The resulting AgNPs were highly stable and maintained their particle size after several cycles of drying at 80 oC and re-dispersion in water. Moreover, the AgNPs on the clay surface melted at a low temperature (110 oC), observed by SEM. Such AgNPs may have potential applications for fabricating silver arrays or conductors at low temperature. Part 2. Nanohybrids of silver nanoparticles (AgNPs) decorated on the surface of multiwalled carbon nanotubes (Ag/MWNT) were synthesized via the in situ reduction of AgNO3 in N,N-dimethylformamide (DMF) and water mixtrues. The process required the presence of a poly(oxyethylene)-backboned oligoimide (POE-imide), which stabilized the dispersion of MWNTs and AgNO3 initially, and subsequently the reduced Ag0 nanoparticles. AgNPs in the range of 8–30 nm diameter were generated and some of these were directly attached to the MWNT surfaces, as observed by transmission electron microscopy (TEM). Without the presence of POE-imide, AgNO3 can only be reduced into Ag0 mirror by DMF slowly and deposits on the side of the reactor wall. The kinetic formation of these nanohybrids was characterized by UV-visible (UV-vis) absorption for MWNTs at 550 nm and AgNPs at 420 nm. The single MWNT tubes of decorated with AgNPs (20–30 nm) were isolated by washing off the dispersant and free AgNPs. The synthesis involving an organic dispersant provides a convenient and facile method for preparing Ag/MWNT nanohybrids from the unmodified MWNTs. Part 3. We fabricate a flexible and surface conductive films by hybridizing silver nanoparticles on multi-walled carbon nanotubes (Ag/CNT) via an in situ silver nitrate reduction in poly(oxyethylene)-imide (POE-imide) dispersion. The POE-imide copolymers provided dual functions for homogenizing CNT dispersion in DMF/H2O mixture and subsequently stabilizing the Ag/CNT nanohybrids during the solvent evaporation into films. By simple coating on polyimide substrate and heating to 160 oC, the generated silver nanoparticles (AgNPs) migrated to surface and aggregated to larger size of 100−150 nm. Continuing heating at 170 oC and 350 oC, the film surface appeared to have color changes from golden to milky-white with lower sheet resistance of 2.2 x 10-1 Ohm/sq and 2.7 x 10-2 Ohm/sq, respectively. The enhancement of surface electrical conductivity was attributed to the AgNPs migration through CNT network and melt into silver granule connection while simultaneously annealing at the preferable temperature of 350 oC. The mechanistic aspects were elucidated by surface observation on a scanning electronic microscope, measurement of organic degradable temperature by thermal gravimetric analyzer and silver characterization by wide-angle X-ray diffraction. The synthesis is viable for making flexible polyimide film exhibiting an unprecedented high conductivity that easily lighting a light-emitting diode lamps.

高透明性聚醯亞胺混成複合材料合成與光電應用之研究

2021-06-15T11:15:24Z

標題: 高透明性聚醯亞胺混成複合材料合成與光電應用之研究; Synthesis and Characterization of Highly Transparent Polyimide Hybrid Materials for Optoelectronic Applications 作者: Chia-Liang Tsai; 蔡家量摘要: 本論文分成六個章節，第一章為總體序論。第二章由一新的簡便合成方法來合成含有羥基可溶性Polyimidothioethers(PITEs)並由其製備polyimidothioethers-奈米晶二氧化鈦（PITEs-TiO2）且具有高的二氧化鈦含量（~50wt％）和厚度達15±3um的光學膜。此外，透明可繞的聚醯亞胺-奈米晶二氧化鈦(PI/TiO2)的混合具有高的二氧化鈦含量（~50wt％）和厚度達15±3um的光學膜由新的可溶性含有羥基之聚醯亞胺Polyimide(PI)所製備而成。羥基在PITEs和PI的骨幹可以提供有機-無機鍵結點並且通過控制丁醇鈦/羥基的莫耳比來製備獲得均勻之混成溶液。由此方法可成功獲得可繞有機無機混成膜，並擁有良好的表面平坦性，熱尺寸穩定性，可調諧的折射率（1.63至1.80，在633nm波長下），和高的光學透明度。基於此系列之有機無機複合膜所製備三層抗反射塗層具有在可見光範圍內小於0.5％的反射率，顯示其潛在的光學應用性。然而，在所獲得之PI-TiO2的光學穿透度光譜中顯示，因TiO2的能隙(3.2eV)使得在400 nm波長的穿透度有明顯得減少，而導致複合膜有淡黃色的顏色。所以，在此有機-無機混摻系統中，選擇之無機材料不僅需要能夠提升折射率，更為重要的是能夠保有原PI的光學透明度。因此，第三章成功製備出高熱穩定性含二氧化鋯的聚醯亞胺混成膜（PI/ZO2），且具有優良的光學透明性。所得到的ZrO2奈米粒子不僅可以良好地分散在聚醯亞胺基材中，此PI/ZO2複合薄膜也顯示了優異的光學透明度，可調諧的折射率和阿貝數，分別高達1.804和32.18，這對於光學元件是至關重要的。此外，由於ZO2具有較大的能隙，故PI/ ZO2混合膜對比於相應的PI/ TiO2系統在可見光區域也表現出高阿貝數和透明性。因此，本研究表明，PI/ ZO2複合薄膜具有更優異的優點來應用於光學元件上。第四章則由, 4’-bis(4-amino-3-hydroxyphenylthio)diphenylsulfide (3SOH-DA) 二胺和4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)二酸酐合成出一種新穎的可溶液加工的具有羥基鍊側基和含硫之poly(o-hydroxy-imide) 3SOH-6FPI並應用於記憶體元件上。為了提高元件的記憶行為，導入不同量的TiO2於3SOH-6FPI中並探討TiO2的含量相應的元件記憶行為。混成膜中由不同TiO2含量0wt％至50wt％明顯增其記憶時間，由DRAM，SRAM至WROM的可調控記憶時間之存儲元件且具有高的開/關電流比（108）。另外，由電流-電壓IV特性的結果顯示，結晶相的TiO2擁有更高的電荷捕集能力，使元件在ON的狀態有更長的停留時間。在第五章中，更進一步設計及合成一系列含有具有羥基鍊側基和含硫之聚醯亞胺3SOH-RPI，且由導入不同拉電子能力的二酸酐（CHDA < 6FDA < DSDA）到聚醯亞胺主鍊上，而得到相對應的記憶體儲存行為（None, DRAM, SRAM）。且為了提高元件的記憶行為，導入不同含量的ZrO2於3SOH-RPI中並探討ZrO2的含量相應的元件記憶行為。此外，也比較由含有不同HOMO和LUMO能階的ZrO2和TiO2導入混摻系統中，來比較相同無機含量下，對元件記憶行為的影響。第六章節為結論。; This study has been separated into six chapters. Chapter 1 is general introduction. In Chapter 2, a new facile synthetic route were developed to prepare flexible polyimidothioethers-nanocrystalline-titania (PITEs/TiO2) and polyimides–nanocrystalline-titania (PIs/TiO2) hybrid optical thin films with high titania content up to 50 wt% and thickness of 15 µm. The hydroxyl groups at the backbone of the PITEs and PIs could provide the organic-inorganic bonding sites and resulted in homogeneous hybrid solutions by controlling the mole ratio of titanium butoxide/hydroxyl group. The flexible hybrid films were successfully obtained and revealed good surface planarity, thermal dimensional stability, tunable refractive index (1.63 to 1.80 at 633 nm), and high optical transparency. In addition three-layer anti-reflection coating based on the hybrid films was prepared and showed a low reflectance 0.5% in the visible range indicated its potential on optical applications. However, the optical transparency of the obtained PI/TiO2 hybrid films reduced dramatically at wavelength around 400 nm attributed to the low band gap of TiO2 (3.2 eV), resulting in pale yellow color of the hybrid films. Thus, by choosing species of inorganic materials in the hybrid system for enhancing the refractive index without optical transparency in visible light region is an important issue. Therefore, chapter 3 describes the novel thermally stable zirconia-containing polyimides (PI/ZrO2) with excellent optical properties have been prepared successfully. Thus, the zirconia nanoparticles were well dispersed in polyimide matrix. The obtained flexible PI/ZrO2 hybrid films revealed excellent optical transparency, tunable refractive index and Abbe number up to 1.804 and 32.18, respectively. In addition, the PI/ZrO2 hybrid films also exhibit higher Abbe number and transparency in visible light region than the corresponding PI/TiO2 system due to larger energy band gap of ZrO2. Thus, the study demonstrates the PI/ZrO2 film based on its advantages and potential is more superior for optical application. In the other hand, chapter 4 introduce a novel solution-processable sulfur-containing poly(o-hydroxy-imide) 3SOH-6FPI with pendant hydroxyl groups and the corresponding polyimide 3SOH-6FPI/TiO2 hybrids were synthesized from the diamine 4,4’-bis(4-amino-3-hydroxyphenylthio)diphenylsulfide (3SOH-DA) and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), for memory application. To enhance the memory behavior, different amounts of TiO2 were introduced into 3SOH-6FPI and investigated the corresponding tunable memory properties. The resulting hybrid films having different TiO2 concentration from 0 wt% to 50 wt% exhibited electrically programmable digital memory properties from DRAM, SRAM, to WROM with high ON/OFF current ratio (108). Furthermore, according to the results of the current-voltage I-V characteristics, the crystalline phase of titania reveals higher trapping ability to increase the retention time at the ON state. In order realize the switching mechanism of 3SOH-6FPI/TiO2 hybrids memory devices, molecular simulation and electrode effect were also discussed in this study. Moreover, chapter 5 describes the series solution-processable sulfur-containing poly(o-hydroxy-imide)s 3SOH-RPI with pendant hydroxyl groups and the corresponding 3SOH-RPI/ZrO2 PI hybrids were synthesized from the diamine 3SOH-DA and dianhydrides of CHDA, 6FDA, and DSDA, respectively, for memory application. By introducing acceptors with different electron-withdrawing capability (CHDA < 6FDA < DSDA) into polyimide backbones, the obtained polymer memory devices show the memory behaviors of None, DRAM, and SRAM, respectively. In order to facilitate and enhance the memory effects, different amounts of ZrO2 were incorporated into 3SOH-RPI to investigate the corresponding memory properties. Moreover, in order to deeply confirm the memory switching mechanism of 3SOH-RPI/ZrO2 hybrids, the devices fabricated both from PI/ZrO2 and PI/TiO2 hybrid films were used to demonstrate the effect of LUMO energy level of ZrO2 and TiO2 on the memory characteristics and retention time in this study. Chapter 6 conclusions.