臺灣博碩士論文加值系統

時間分辨小角光散射(TRSALS)技術是解析軟物質在介觀尺度中，時間和空間複雜性的重要工具。在本篇論文中，我們利用時間分辨小角光散射實驗探討agarose凝膠的形成機理與結構特徵間之關係。

首先，從Hv散射和時間追蹤流變實驗，我們建議agarose分子鏈在溶膠狀態應該表現出單螺旋worm-like chain 的特徵，此外，agarose凝膠的凝膠化過程可以被分劃為以下三個階段：
(1) 漲落階段(t < tnucl)；
(2) 熟化階段(tnucl < t < taging)，微纖網目在此階段形成，但其結構與性能仍不斷的在提高；
(3) 老化階段(t > taging)，真正的平衡網目不會出現，此結果與早期我們認為微纖狀網目是遠離平衡的結構是可以相互呼應的。

接著，儘管在凝膠化過程中的Vv散射圖樣呈現出spinodal-like的圖案，但經由我們對其散射細節進行分析之後，我們發現agarose凝膠的三維網目結構形成機制並非如早期所認為的是來自於相分離失穩分解或是分形聚集機制。除此之外，藉由散射數據取得的表觀分形維度以及掃描式電子顯微鏡(SEM)的觀測結果，我們建議agarose網目結構應具有”無標度網路”的特徵。因此，我們有空間重新考慮微纖網目的形成機制，在這一點上，我們的相干結構演化模型對於這樣的凝膠化現象或過程的描述提供了一個良好的起點。
 

Time-resolved small-angle light scattering (TRSALS) is an important technique to study the temporal spatial complexity of soft matter on a mesoscopic length scale. In this thesis, from the Hv scattering and time-trace rheological experiments ,we suggest that the molecules should exhibits a worm-like chain with the single helix conformation in sol state and show that the gelation process of the agarose hydrogel can be divide into three stages:
(i) the structural fluid stage (t < tnucl)
(ii) the ripening stage(tnucl < t < taging), the fibrillar network is formation, but the structure and properties are continued enhancement.
(iii) the aging stage (t > taging), no true equilibrium network was observed, the result is consistent with our previous studies that the fibrillar network is a polycrystalline off- equilibrium configuration.

On the other hand, although the Vv scattering does show a ring pattern in gelation process, our detailed analysis rejects the early opinion that the agarose gelation is induced by the spinodal decomposition or by the fractal aggregation. Moreover, we suggest that the network structure of the agarose hydrogel is characterized by a scale-free network. Thus, there is room for reconsidering the current opinion on the formation mechanism of the fibrillar networks. At this point, our coherent structure model is a good starting point in the description of the phenomenon or process.

Abstract II
Acknowledgements III
Contents IV
Chart Catalogues V
Principal Notation VIII
Chapter 1. Introduction 1
1.1 Literature Review of Agarose Hydrogels 2
1.1.1 Helical Structures of Agarose Chains 2
1.1.2 Gelation Mechanism of Agarose Hydrogel 4
1.2 General Discussion on Forming a Fibrillar Network 7
1.3 The Purpose of This Thesis 9
Chapter 2. Theoretical Background 10
2.1 Classical Approximations 11
2.2 Scattering Function 12
2.2.1 Scattering Function of Sphere Scatterer 12
2.2.2 Scattering Function of Rod Scatterer 15
2.3 Scattering Modeling of the Crystalline Fibril 18
Chapter 3. Experimental Section 22
3.1 Materials and Preparation of Agarose Hydrogels 22
3.2 Small-Angle Light Scattering (SALS) Measurement 22
3.2.1 Instrumental Setup 22
3.2.2 Calibration 23
Chapter 4. Results and Discussions 26
4.1 Hv Scattering Patterns of Agarose Hydrogels 26
4.2 Vv Scattering Patterns of Agarose Hydrogels 30
4.3 Structural Formation of Agarose Hydrogels 35
4.4 Concept of Scale-Free Network 44
Chapter 5. Conclusion 47
Reference 48

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