本研究主要探討在聚葡萄糖(dextran)水膠中固定合成前驅高分子(dex-MA)的取代度(定義在100個葡萄糖單體中接上methacrylate group的個數)，分別加入不同體積比例的聚乙二醇(PEG)，交聯後形成在網路結構交聯點間的鏈段上具有PEG側鏈結構的水膠，藉由改變PEG在高分子中的比例來探討不同接枝參數形成之網路結構對網目孔隙的影響。
在側鏈的影響下水對PEG的親合力大於dextran，使水膠含水率隨PEG在水膠中含量遞增。由應力-應變實驗的結果顯示，彈性模數(G)值隨PEG含量增加而上升，可知水膠內的有效交聯密度(νe)隨著側鏈的含量增加而變大。側鏈密度增加，造成水膠網路的交聯密度增加，使交聯點間的分子量（Mc）隨著密度增加而變小；水膠網目大小（ξ）則隨著含水率增加而變大。
利用BSA和Vitamin B12作為釋放實驗的溶質，藉由改變水膠的取代度及含水率，探討溶質在水膠中「擴散自由體積」與「擴散路徑長度」如何受溶質與水膠分子參數控制。根據自由體積理論，由ln(Dm/D0)對(1/H -1)作圖發現，隨著水膠中PEG的含量增加，高分子鏈運動性增加，則直線斜率的絕對值越小；而改變溶質的半徑發現，斜率和溶質半徑近似1.4次方成正比，此結果並不符合Yasuda自由體積理論中斜率和溶質的平方成正比，顯示溶質在水膠中擴散的速率，除了溶質半徑外，還需要考慮溶質和高分子、溶劑間的交互作用力。
當水膠取代度的增加及含水率的增加，網目變大，溶質和網目大小的比值變小，因而減少溶質在水膠中擴散的繞曲度，當溶質直徑和網目大小的比值在0.1和0.8之間，繞曲度的實驗值與Renkin理論值誤差達200％左右，且隨著λ值的增加，實驗值和理論值的差距增加。因此我們推測，影響溶質在水膠中擴散的繞曲度，除了溶質直徑和網目大小的比值外，溶質的形狀也是影響繞曲度的因素之一。

In this study, dextran hydrogels grafted with various volume content of PEG were prepared by polymerization of aqueous solution of glycidyl methacrylate derivatized dextran(dex-MA). The objective is to demonstrate the influence of grafting parameters on the mesh size in PEG-grafted dextran hydrogels.
With increasing contents of PEG, PEG grafted chains make water contents of hydrogels increased. In the compressive stress experiment, the modulus and the effective crosslinking density (ve) increased with the increasing contents of grafted chains. As the crosslinking densities increase, the molecular weights between the crosslinks (Mc) of gels decrease. The hydrogel mesh size (ξ) increasing of water contents increased.
The releases of BSA and Vitamin B12 from hydrogels varying in degrees of substitutions and water contents, are investigated to understand the “free volume of diffusion” and “length of diffusion path” in terms of the molecular parameters of diffusants and gels.
In addition, as the water contents increase, the tortuosity of solutes diffusion in the gels decrease. As the ratio of diameter of solutes to mesh sizes of the gels lie between 0.1 to 0.8, a significant deviation of 200% between the experimental and predicted values is found. However, there’s a large deviation between the experimental and the predicted values at higher ratio. The theoretical lines can’t overlap with experimental data, therefore, it’s believed that the shape in solutes can also affect the tortuosity of solutes diffusion in gels.

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