精準合成物理交聯型poly(urea/malonamide)側鏈之形狀記憶聚氨酯

Abstract

本論文使用精準控制的poly(urea/malonamide)側鏈，探討其應用在形狀記憶聚氨酯的效果。可精準控制分子量及鏈長的poly(urea/malonamide)樹枝狀(DG 系列)與直線型(LG 系列)氫鍵側鏈提供聚胺酯的物理交聯；聚氨酯主鏈SPU使用同一鍋以確保聚氨酯主鏈的分子量及其分佈相同。 聚胺酯利用MDI及CAPA®2303 (Mn=3000)為主體，導入反應性的小分子雙醇，製備具有可後修飾官能基azetidine-2,4-dione之聚胺酯Side-chain polyurethane (SPU)主鏈。反應性官能基azetidine-2,4-dione作為交聯點，使用不同側鏈接枝率導入精準合成的不同代數或鏈長之poly(urea/malonamide)側鏈及來調控聚氨酯的氫鍵物理交聯密度。製備出側鏈精準合成的氫鍵物理交聯聚氨酯系統，並比較樹枝狀和直線型側鏈對聚胺酯性質的影響。 由NMR、IR、EA、Mass及GPC分析，確認製備出精準控制分子量或鍊長的poly(urea/malonamide)聚合物，並由DSC分析的結果可知，樹枝狀及直線型poly(urea/malonamide)側鏈，隨著代數提升、氫鍵數量增加可觀察到玻璃轉移溫度的上升。 DMA觀察聚胺酯的機械性質及相轉移tanδ溫度，都因物理交聯密度的增加而提高。其中SPU-DG系列因樹枝狀側鏈本身氫鍵密度高，比直線型側鏈更有效提升了低溫的儲存模數；而SPU-LG系列的直線型側鏈在物理交聯補強聚胺酯機械性質的同時，還能保有明顯的相轉移峰。有別於SPU-DG系列，SPU-LG系列的儲存模數在相轉移區域之後有rubbery plateau region，提升了橡膠態的儲存模數。 利用Thermal mechanical test進行形狀記憶測試，發現SPU-DG系列聚氨酯具有良好的形狀固定率，但形狀回復效果普遍較差。而高代數側鏈的SPU-LG系列聚氨酯具備有良好的形狀固定率及形狀維持率。本研究的形狀記憶效果以S45-DG2.5-50、S45-DG2.5-25、S35-LG2.5-50、S45-LG2.5-50、S45-LG2.5-25和S45-LG3.5-50聚胺酯的效果最佳，形狀回復率和形狀固定率都維持在90%以上。

With precise synthetic control of hydrogen bond-rich side chains, shape memory polyurethanes (PUs) were prepared. These PUs comprising dendritic (DG series) or linear (LG series) polyurea/malonamide hydrogen bond-rich side chains with uniform chain lengths, providing physical crosslinking interactions to PUs. With the reactive functional group, azetidine-2,4-dione as the side chain of SPU to be a crosslinking site, different grafting ratios with various chain lengths of poly(urea/malonamides) were incorporated onto SPU. Consequently the physical crosslinking density could be adjusted. Via NMR, IR, EA, Mass and GPC analysis, we were able to confirm that the precise control of the poly (urea/malonamide) chain lengths were obtained. Differential scanning calorimeter (DSC) showed that, with the increasing chain length of the dendritic or linear poly (urea/malonamide), the glass transition temperature rose as a result of increasing hydrogen bonding interactions. Cyclic thermal-mechanical tests were conducted for evaluating shape memory properties. A higher E'low value would make the movement of the polymer chains limited at low temperatures. Consequently the shape retention was enhanced. Moreover, a significant phase transition peak (tanδmax) and a broad rubbery plateau region would also help to improve shape recovery. Because of this, SPU-DG series exhibited excellent shape retention, but relatively poor shape recovery. On the other hand, the SPU-LG series with higher generation side chains exhibited excellent shape and shape retention. S45-DG2.5-50, S45-DG2.5-25, S35-LG2.5-50, S45-LG2.5-50, S45-LG2.5-25 and S45-LG3.5-50 exhibited excellent shape memory effect, with both shape recovery and shape retention higher than 90%. It is concluded that these well-defined PUs with excellent shape-memory effect have been successfully developed in this work.