聚氨酯(Polyurethane, PU)之形狀記憶行為，其機制為利用PU中軟段的PCL之熔點(Tm)及結晶溫度作為兩個相轉移溫度，並藉由軟硬鏈段的相互影響，使之擁有記憶不同形狀的功能，且最後可回復至初始形態。
本研究分別利用中空管狀高嶺土(Halloysite nanotubes, HNTs)及奈米纖維素纖維(cellulose nanofiber, CNF)來改質PU的系統，藉此改善循環記憶效應不佳，製備出擁有高回復率及高固定率的形狀記憶高分子。本研究利用HNT表面上的羥基(-OH)與PU預聚物末端的異氰酸酯官能基(-NCO)產生共價鍵，除形成網狀交聯的結構藉以提供在材料內部儲存應力所需的硬鏈段外，更使兩物質在非晶區產生結晶，以記憶較多應力，相對地在回復時亦能釋放較多應力。利用這兩部分來改善材料回復形狀的性能，以及比較兩者對形狀記憶效應的影響；而因應相同增強硬段的概念，本研究另外選擇一具可撓性且表面同具有-OH的CNF，來比較其不同改質的特性。
本研究分別探討0、0.5、1和3wt%的HNT及CNF對形狀記憶效果的影響。經試驗的結果得出，HNT及CNF的改質皆能有效的改善形狀記憶回復率至約90%並同時保持99%以上之固定率。

Polyurethanes nanocomposites were synthesized with 4,4’- Methylene diphenyl diisocyanate (MDI), poly(Ɛ-caprolactone) (PCL) and nanofiller. The hydroxyl groups on halloysite (HNT) and cellulose fibers (CNF) were reacted with MDI to form a crosslinked network structure. Effects of diffrtent content on the surface morphology, mechanical, thermal, thermo-mechanical and shape memory properties were investigated by using tensile tester, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA), respectively. The crosslinking density of the polyurethanes was determined by using swelling test.
The results showed that both PU/HNTs and PU/CNF nanocomposites exhibited a significant improvement in the thermal, mechanical and shape memory properties comparing with pristine polyurethane. The shape memory properties improvement may be attributed to appreciable crosslink density.

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