含金剛烷規則樹枝狀形狀記憶聚氨酯的合成與鑑定

Abstract

本論文利用具有反應選擇性的雙官能基單體 (4-isocyanato-4’(3,3-dimethyl-2,4-azetidino)diphenylmethan) (IDD)，以收歛法製備出一系列以金剛烷為末端基團的poly(urea/malonamide)規則樹枝狀分子，探討其應用在形狀記憶聚胺酯的效果。 以IDD和構築單元交替反應，isocyanate和一級胺在低溫下反應成urea鍵結，再以azetidine-2,4-dione和一級胺在高溫下形成malonamide鍵結，可免除催化劑添加、活化、去保護等步驟，逐步得到一系列具有窄分子量分布特性的樹枝狀分子，urea/malonamide的分子設計賦予樹枝狀分子豐富的氫鍵。將規則樹枝狀分子改質成聚胺酯的雙醇鏈延長劑接在側鏈，或單醇封端劑接在主鏈，經由豐富的urea/malonamide鍵結增加硬鏈段氫鍵密度，加強材料性質。 由IR、NMR、Mass、EA分析poly(urea/malonamide)，證實確實製備出樹枝狀分子，並以GPC確認規則樹枝狀分子擁有窄分子量分佈。TGA與DSC分析poly(urea/malonamide)與聚胺酯的熱性質，確認poly(urea/malonamide)的玻璃轉移溫度隨代數而上升，並由DSC了解聚胺酯的相轉變行為。由萬能拉力機、DMA分析聚胺酯，萬能拉力機顯示聚胺酯在室溫下的機械性質，發現結晶與硬鏈段含量皆對聚胺酯的機械性質有影響。DMA觀察聚胺酯在不同溫度下的儲存模數，發現高溫儲存模數會隨著物理交聯密度的增加而提高，低溫則受到材料結晶能力的影響。形狀記憶能力同樣以DMA量測，發現擁有高代數側鏈的聚胺酯具有較穩定氫鍵物理交聯，因此在多次拉伸後仍擁有良好的形狀記憶能力，本實驗以SPU35-G2.5、SPU40-G2.5、SPU45-G2.5的性質最佳，擁有97%以上的高形狀維持率，且經過多次拉伸，形狀回復率維持在94%以上，並在手拉測試中可在瞬間完成形狀回復。

A series of poly(urea/malonamide) dendrons with peripheral adamantyl groups were incoporated into polyurethanes to investigate their shape memory behavior. The dual functional (4-isocyanato-4’(3,3-dimethyl-2,4-azetidino)diphenylmethan) (IDD) was used to synthesize a series of hydrogen bond-rich poly(urea/malonamide) dendrons via convergent route. With high reactivity of isocyanate and reaction selectivity of azetidine-2,4-dione, a sequential method to prepare dendrons without protection-deprotection process was developed under mild condition The dendrons were further introduced into polyurethanes, providing physical crosslinking interactions to polyurethanes. Well-defined poly(urea/malonamide) dendrons were successfully prepared as evidenced by analyses of IR, NMR, and Mass spectroscopy, and EA. GPC analysis showed that the molecular weights of dendrons in this study are mono-dispersed. Differential scanning calorimeter (DSC) revealed that with the increasing generation of dendritic poly (urea/malonamide), the glass transition temperature rose as a result of increasing hydrogen bonding interactions. Universal tensile machine (UTM) and dynamic mechanical analysis (DMA) were utilized for evaluating mechanical and shape memory properties of side-chain dendritic polyurethanes (SPUs) and end-capped polyurethanes (EPUs). A series of linear polyurethanes (LPUs) were prepared for comparison. All the EPUs were fragile under room temperature, which were not available for mechanical testing. UTM shows that SPUs are more rigid than LPUs under room temperature due to better crystallinity or stronger physical crosslinking interactions. DMA shows that SPUs exhibited higher storage modulus than did LPU at low temperatures owing to higher crystallinity. This would further enhance shape retention properties. On the other hand, the higher density of physical crosslinks in SPU-G2.5 than those in SPU-G1.5 and LPU would also enhance storage modulus of SPUs-G2.5 at high temperatures. This would improve shape recovery properties. The result of cyclic shape memory test shows that shape memory process of SPUs took less than 3 seconds. Furthermore, SPUs with high soft segment content exhibited excellent shape retention over 97%, and the SPU40-G2.5 sample exhibit shape recovery over 95% even after 3 rounds of cyclic shape memory test. It is concluded that the enhanced physical crosslinking interactions improved shape memory effect in polyurethanes, along with a proper tuning of hard segment content. A series of PUs with excellent shape-memory effect have been successfully developed in this work.