本研究利用1,1,3,3-四甲基胍作為促進劑，使不同臂數之多元醇對α-胺基酸N-羧酸酐進行開環聚合合成一系列六臂和十二臂之雙嵌段聚胺基酸，並將其製備成水膠。雙嵌段聚胺基酸以賴胺酸做為第一鏈段，以3:1的比例分別嵌段不同疏水性寡聚胺酸(芐基半胱胺酸、苯丙胺酸、酪氨酸與芐基酪氨酸)。藉由調控不同臂數及嵌段不同疏水性寡聚胺酸，來探討其對自組裝結構及成膠性質的影響。臨界成膠濃度測試及水膠的流變性質測試都顯示，不同臂數及嵌段不同疏水性寡聚胺酸對兩者有很大的影響。因為十二臂水膠的不對稱型及立體障礙，十二臂的水膠有著較高的臨界成膠濃度及較低的儲存模量。其中六臂聚賴胺酸嵌段聚芐基半胱胺酸(6s-PLL15-b-PBLC6)有本研究中最低的成膠濃度(2 wt%)及最高的儲存模量(約6500 Pa)。除此之外，多數的水膠都具有優異的回復性質。以FT-IR及CD光譜分析發現，疏水性寡聚胺酸能夠形成幫助水膠凝膠化之β-折版構型。從XRD中也確認了苯環之間π-π堆疊的峰值。綜上所述，我們推測水膠的成膠性及其機械強度來自於分子內及分子間的氫鍵作用力、疏水性作用力及π-π堆疊作用力。最後我們也藉由SAXS及SEM分別分析雙嵌段聚胺基酸水膠在微觀自主裝及巨觀聚集的結構。可以發現藉由嵌段不同疏水性寡聚胺酸，雙嵌段聚胺基酸水膠會自組裝形成球型或圓板型，隨著水膠濃度的下降，雙嵌段聚胺基酸會吸水膨潤使其尺寸變大。而在SEM巨觀視野下，雙嵌段聚胺基酸水膠會形成多孔的3D結構或是類似於窗簾的平面結構。

A series of 6-armed and 12-armed diblock copolypeptides were synthesized to investigate their self-assembly and hydrogelation behavior in water. These star-shaped diblock copolypeptides were synthesized by N-carboxyanhydrides (NCAs) ring opening polymerization using TMG to promote the alcohol initiators. The diblock copolypeptides comprised of poly-L-Lysine (PLL) as 1st block and separately tethered with four different hydrophobic oligopeptides (L-Phenylalanine, S-Benzyl-L-Cysteine, O-Benzyl-L-Tyrosine and L-Tyrosine) at the ratio of 3:1. All the star-shaped copolypeptides except 12s-PLL16-b-PLY3.7 were hydrogel formable. Notably, 6s-PLL15-b-PBLC6 had the lowest critical gel concentration (CGC) of 2%. The CGC and mechanical strength showed strong dependence on arm number and different hydrophobic residue that attached on PLL. Also, some of the hydrogel exhibited shear-thinning and good recovery behavior. Characterization of CD spectroscopy and FT-IR confirm the coexistence of random coil and β-sheet/β-turn conformation. XRD analysis indicated the presence of π-π stacking. We suggested that hydrogel formation was driven by the delicate balance between hydrogen bonding, π-π stacking and hydrophobic interaction. Also, β-motifs conformation induced by hydrophobic oligopeptide was favorable for gelation and could increase the mechanical strength of hydrogel. From SAXS and SEM analysis, we found that diblock polypeptide with differently tethered hydrophobic oligo peptide had strong influence on both the microscopic and macroscopic structure. Polypeptides would self-assembled into spherical or flat disk structure, and consequently aggregated into 3D porous or curtain-like structures. In conclusion, this study illustrated the tunability of polypeptide hydrogels by varying the arm number or hydrophobic oligopeptides.

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