本研究將聚乙二醇(PEG)的聚合度固定為91(PEG分子量為4000 g/mol)，合成兩種不同疏水鏈段聚合度(聚合度為264及918)的聚乳酸與聚乙二醇三團聯共聚物(PLLA-PEG-PLLA)。使用螢光探針法測量臨界微胞濃度，並將不同電解質(氯化鈣或氯化鈉)加入共聚物溶液中，改變電解質濃度及溶液的環境溫度，接著利用臨界微胞濃度計算其微胞化熱力學參數，再使用動態光散射儀測量微胞粒徑，探討電解質濃度、電解質物種及高分子疏水段聚合度對臨界微胞濃度、微胞化熱力學參數及微胞粒徑之影響。
從臨界微胞濃度實驗可得知，臨界微胞濃度會隨著溫度上升而增加，也會隨著電解質濃度增加而下降。在溶液中活性係數較大的電解質(即NaCl)，使臨界微胞濃度下降較為明顯。疏水鏈段聚合度愈大時，臨界微胞濃度愈小，且電解質濃度效應及電解質物種效應愈不明顯。利用salting係數比較不同共聚物在不同的電解質溶液中salting效果，可得知salting係數會隨著溫度上升，疏水鏈段聚合度愈小或平均離子半徑愈小而愈大，鹽析效果愈明顯。
從微胞化熱力學參數的計算結果得知，微胞化自由能之絕對值及微胞化標準熵(正值)隨著電解質濃度增加而增加，微胞化標準焓(負值)之絕對值會隨著電解質濃度增加而減少，且電解質在溶液中活性係數愈大，影響較為明顯。共聚物中疏水鏈段聚合度愈大，微胞化自由能之絕對值及微胞化標準熵隨之愈大，而微胞化標準焓之絕對值隨之愈小，且電解質濃度及物種效應較不明顯。不同共聚物在不同的電解質溶液中對微胞化熱力學參數之影響程度也可以利用salting係數來解釋。
在中間共聚物濃度時，使用動態光散射的實驗中，可發現微胞在電解質濃度為0.1 M時，相較於在純水中測得的平均微胞粒徑有四倍以上增加，且較大的粒徑族群出現，表示有聚集產生，平均微胞聚集粒徑隨著電解質濃度增加而更明顯地變大。在NaCl溶液中，測得的平均微胞聚集粒徑較大，微胞聚集也會較為明顯。發現電解質影響微胞粒徑的趨勢與臨界微胞濃度相同。

This study is to synthesize poly(L-lactide)-poly(ethylene glycol)- poly(L-lactide)(PLLA-PEG-PLLA) triblock copolymers with various PLLA segment lengths (degree of polymerization= 264 and 918) and fixed PEG length (degree of polymerization= 91). We use fluorescent probe to determine the critical micelle concentrations (CMC) of triblock copolymer solutions with various concentrations of calcium chloride and sodium chloride over a temperature range of 23 to 45 degrees centigrade, and determine subsequently thermodynamic parameters of micellization. The micelle size is also measured with dynamic light scattering (DLS), showing the effects of electrolyte species and concentrations on the micelle clustering.
Experimental results show that critical micelle concentration increases with rising temperature, and decreases with increasing electrolyte concentration. These two effects on CMC are more significant for electrolyte solutions with higher activity (i.e.,NaCl). CMC is lower for copolymers with longer PLLA block, where effects of electrolyte concentration and species on CMC is less pronounced. The salting coefficients are used to signify the salting out in solutions of various electrolytes and block copolymers. This coefficient increases with rising temperature, decreasing hydrophobic block length in copolymers, and decreasing mean radius of ions in electrolytes.
Calculated thermodynamic parameters of micellization shows that the absolute values of Gibbs energy of micellization, standard entropy of micellization (with positive value) and standard enthalpy of micellization (with negative value) increase with electrolyte concentration, where these three parameters were affected more significantly by sodium chloride than calcium chloride. Moreover, the effects of electrolyte concentration and species on three parameters of micellization were more pronounced for copolymers with shorter hydrophobic blocks. The structural effects of electrolytes and block copolymers were well explained with salting coefficients.
DLS experiment reveals a more than fourfold increase in average micelle size as electrolyte concentration is raised from 0 to 0.1 M, with the appearance of a population with a greater average size. This clustering of micelles becomes more apparent with electrolyte concentration, as indicated with an increasing average size. Sodium chloride affects the micelle size in the same way as CMC.

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