合成不同插層劑對高分子/黏土奈米複合材料物理性質之影響

Abstract

蒙托土應用於高分子材料上，改善了原有高分子的物理性質，例如：熱穩定性、機械性質、阻氣性、尺寸安定性等。這些物理性質改善的程度取決於蒙托土在高分子基材的分散程度，分散程度越好性質提升越顯著，反之則不然。本篇論文分成四部份，主要探討不同插層劑對奈米複合材料物理性質的影響。 1. 本實驗利用乳化聚合的方法製備聚苯乙烯/蒙托土奈米複材，在蒙托土含量3%時為脫層結構，在實驗當中使用POSS與CPC兩種插層劑改質蒙托土，由X-ray鑑定出POSS與CPC都有成功插層進入蒙托土，在TGA實驗中，POSS有效地增加奈米複材的熱穩定性，主要因素是POSS較CPC具有剛性結構，有別於市售的插層劑，其具有長的碳烷鏈較不受熱。GPC分子量分析得知蒙托土會妨礙高分子聚合反應的進行，分子量分布也較廣。 2. 我們合成插層劑APB，其具有金剛烷的官能基，去改質蒙托土製備聚苯乙烯/蒙托土奈米複材，先前文獻利用含磷的官能基作插層劑，目的提升奈米複材的熱穩定性，本實驗研究金剛烷可否取代磷的官能基，作為插層劑另一種選擇。TGA結果顯示金剛烷確實較含磷的插層劑穩定，XRD說明我們所製備的複合材料具有奈米尺寸的分散程度，DSC得知有添加蒙托土的奈米複材玻璃轉移溫度較高，熱膨脹係數也下降44~55%，證實蒙托土有助奈米複材的尺寸安定性。

3. 研究一般商業用插層劑CPC經過改質，套入環糊精對奈米複材的影響。研究結果顯示CPC套環弧精有助將長的碳烷鏈拉直，避免它糾結在一起影響插層效果，在1H NMR得知一個CPC的分子鏈能夠套入兩個環糊精，由XRD與13C NMR可以確定CPC確實有套入環弧精，TGA實驗證實有套環糊精的CPC熱裂解溫度提升50℃左右，主要原因是環糊精保護了CPC的碳烷鏈提升了裂解溫度。 4. 我們首先合成插層劑MBM其具有Benzoxazine官能基，可以進行開環交聯反應，促使蒙托土達到奈米分散程度。我們使用溶劑的摻混方法將Benzoxazine單體與改質後的蒙托土均勻混合，並進行恆溫與非恆溫的交聯動力學實驗，結果得知有添加蒙托土會促進交聯反應提早發生，原因是因為蒙托土表面有催化交聯反應，反應的級數在2.4~2.8之間，活化能隨著蒙托土的含量增加而降低。在3%的蒙托土含量時為脫層結構，大於3%時為插層結構。

Nanoclay-filled polymeric systems offer the prospect of greatly improving many of the properties of their mother polymers. In the recent literature, there have been reports of nanoclay-filled polymeric systems that display significant improvements in tensile and thermal properties, heat distortion temperatures, and resistance to flammability and reduced permeability to small molecules and reduced solvent uptake. A common observation emerging from these studies is that the magnitude of improvement depends strongly on the state of dispersion of the clay layers in the polymer matrix. The experiment work in this dissertation was divided into four areas: 1. We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at up to a 3 wt % content of pristine clay relative to the amount of polystyrene (PS). We used two different surfactants for the montmorillonite: the aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) and the ammonium salt of cetylpyridinium chloride (CPC). The nanocomposite prepared from the clay treated with the POSS containing surfactant is exfoliated, while an intercalated clay was obtained from the CPC-treated surfactant. The value of Tg of the PS component in the nanocomposite is 8 °C higher than the virgin PS and its thermal decomposition temperature (21 °C) is also higher significantly. The presence of the POSS unit in the MMT enhances the thermal stability of the polystyrene. 2. We synthesized intercalation agent APB and prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. We used two different intercalation agents to treat clay: the phosphonium salt (APP) and the ammonium salt (APB). We expected that the intercalation agent APB containing rigid adamantine group also has high thermal stability besides phosphonium group. The molecular weights of polystyrene (PS) obtained from the nanocomposite is slightly lower than the virgin PS formed under similar polymerization conditions. The coefficient of thermal expansion (CTE) was obtained from thermomechanical analysis. A 44~55 % decrease of CTE is observed for APB- and APP-intercalated clay nanocomposites relative to the pure PS. 3. We employed two surfactants for the montmorillonite: cetylpyridinium chloride (CPC) and the CPC/α-CD inclusion complex. The inclusion complex was characterized by X-ray diffraction, 13C CP/MAS NMR spectra, and 1H NMR spectroscopy, and TGA. The 1H NMR spectra of the complexes indicate that the stoichiometry of the complexes is 1:2 (i.e.,one CPC molecule and two α-CD units). The CPC/α-CD-treated clay is more effective than is virgin CPC-treated clay at enhancing the thermal stability of polystyrene. 4. We have used the solvent blending method to prepare polybenzoxazine/clay nanocomposites possessing various clay contents. We synthesized a monofunctional benzoxazine monomer (MBM) and then treated the clay with this intercalation agent. To better understand the curing kinetics of the polybenzoxazine/clay nanocomposites, we performed dynamic and isothermal differential scanning calorimetry (DSC) measurements. The Kissinger and Ozawa methods gave fairly close results for the calculated activation energies, which decreased upon increasing the clay content. The Kamal method－based on an autocatalytic model－suggested a total reaction order of between 2.4 and 2.8.