新型奈米聚乳酸複合材料作為高性能生物聚合物

Abstract

本篇論文介紹一種利用點擊化學反應，將多面體倍半聚矽氧烷寡聚物（Polyhedral Oligomeric Silsesquioxanes，POSS）導入官能化聚乳酸中，使其末端帶有三個多面體倍半聚矽氧烷寡聚物 — tri-POSS PLLA。tri-POSS PLLA是一種非結晶型材料，並具有良好的熱穩定性。 從X光繞射儀微（XRD）及差掃描熱卡計（DSC）的實驗結果中得知，隨著非結晶型的tri-POSS PLLA混掺入市售的純聚乳酸中，由於巨大的立體阻礙基團POSS分散其中，影響了聚乳酸分子鏈段的排列，進而降低其複材的結晶程度；在此同時，tri-POSS PLLA也扮演一種良好的相容劑，成為無機補強材料-POSS與聚乳酸之間相容的良好媒介，補強了純聚乳酸的熱性質及機械性質：在僅須少量的添加量（5％ 以下），其複材的玻璃轉移溫度與純聚乳酸相比，沒有明顯的變化，但卻大幅的增強其複材的拉伸強度、拉伸模數、及儲存模數。 從電子顯微鏡中可觀察出其複材的球晶密度沒有隨著tri-POSS PLLA的添加而有所改變。隨著降解的時間增加，其複材的水解速度也與純聚乳酸相似，表示了tri-POSS PLLA 的添加並無改變其純聚乳酸原有的生分解性質，維持本身環境友善之特質，也進一步改善其它不足的物理性質，包含增強其機械性質、提高其阻氧性，使其在食品包裝材料或其它領域的應用上將更具發展潛力。

This thesis describes a new polyhedral oligomeric silsesquioxane (POSS)-modified poly(L-lactide), tri-POSS PLLA, which contains three POSS end-groups, synthesized through the click reaction of mono azide -functionalized POSS with tripropargyl PLLA. Tri-POSS PLLA exhibits an amorphous phase and good thermal stability. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results of the tri-POSS PLLA in the solid state indicate a reduction in the degree of molecular arrangement because crystal formations were prohibited by the bulky POSS groups. Moreover, tri-POSS PLLA also behaves as an effective compatibilizer that enhances the thermo-mechanical properties of the commercial Polylactide (PLLA). A tri-POSS PLLA (5 wt%)/PLLA (95 wt%) nanocomposite exhibits much higher enhancement of tensile strength and tensile modulus as compared to that of PLLA. The storage modulus has also been significantly improved in the tri-POSS PLLA/PLLA nanocomposites with respect to PLLA, whereas the glass-transition temperatures vary slightly between PLLA and the tri-POSS PLLA/PLLA nanocomposites. However, the overall nucleation density of PLLA spherulites is unchanged, while the crystal structure of PLLA is not modified in the tri-POSS PLLA/PLLA nanocomposites. In addition, the hydrolytic degradation ratio of tri-POSS PLLA/PLLA system is similar to that of other PLLA derivatives, indicating that incorporation of tri-POSS PLLA into PLLA do not appreciably change its original degradable potential, thus resulting in not only superior mechanical performance but also in significant reduction of oxygen permeability, both of which can have profound impacts on the food packaging technologies and other applications.