物理與化學交聯明膠的流變性質研究

Abstract

生物高分子材料之機械性質在實際應用上是至關重要的因素，尤其以人工血管、腸膜等組織，當生物組織擴大變形時，組織會變得堅硬，此為應變剛硬(strain-stiffening)現象。生物聚合凝膠系統中之高分子鏈間應變剛硬之現象，皆以物理性交聯產生網狀結構進行探討，然解釋之論點卻無法完全適用於全部的物理性交聯系統，更甚者，文獻上仍未有學者探討化學性交聯材料之應變剛硬現象。近期，Tung et al在反蠕蟲狀微胞(Reverse wormlike micelles)系統中指出，高分子溶液在無物理/化學交聯與鏈間糾纏點(Entanglements)作用力存在下，卻依然保有應變剛硬之現象發生；並推論高分子鏈間作用力係導致應變剛硬因素之一。故本研究以明膠做為研究材料，首先以物理性交聯與化學性交聯方式，形成永久性網狀結構(Permanent network)，探討物理性與化學性應變剛硬現象之差異。利用兩種不同交聯方式，進一步討論高分子交聯方式、鏈間交聯密度及分子鏈間作用力等因素於應變剛硬現象之影響。研究中使用流變儀探討高分子溶液運動行為，熱示差掃瞄卡量計分析高分子鏈間之作用力，了解明膠網狀結構中鏈間作用力的重要性，並藉由溫度和時間來控制交聯度，探討鏈間作用力的影響程度。

The mechanical properties of soft biological tissues are essential to their physio-logical functions and cannot easily be duplicated by synthetic materials. Unlike simple polymer gels, many biological materials will become stiffer as they are strained , including blood vessels and mesentery tissues. Therefore to prevent large deformation that could threaten tissue is the critical consideration on biological polymers. Until now, most strain-stiffening phenomena of biopolymer gel system that are product by physical crosslinking methods have studied in literatures； however, there has been not a universal explanation which could be fully applicable to all the physical -crosslinked gel systems. On the other side, strain-stiffening phenomena that occur in the chemical-crosslinked materials have yet not been explored. Recently, Tung et al pointed out that in the reverse wormlike micelles system the polymer solutions still retain the strain-stiffening phenomena even without physical, chemical cross-linking and the interaction between entanglement points. Tung et al supposed that the inter-molecular interactions might be one of significant factors to strain-stiffening . In this research, we utilized gelatin as the research material, whose permanent network structures are product by physical-crosslinking and chemical-crosslinking procedures. We mainly concentrate on the differences of strain-stiffening phenomena between the physical and chemical-crosslinked gels. In summary, we investigate cross-linking densities and intermolecular interactions in physical and chemical-crosslinked gels how to affect the strain-stiffening phenomena, respectively. We used rheometers in this study as the efficient tool to investigate the dynamic behaviors of polymer chains. Besides, Differential Scanning Calorimeter (DSC) could help us understand the in-teractions between polymer chains by volume analysis, and hence we know the im-portance of intermolecular interactions in gelatin network structures. Above all meas-urements, we control the temperature and observation time to explore the interactions between polymer chains.