本研究使用聚乙二醇單甲醚與左旋-丙交酯以開環聚合方法合成聚乙二醇單甲醚-聚乳酸(methoxypoly(ethylene glycol)-poly(L-lactide))(mPEG-PLLA)雙團聯共聚物。將其中親水段mPEG聚合度固定為113，並合成兩種PLLA疏水段(聚合度為168、 35和301)的共聚物，利用凝膠滲透層析儀(GPC)對共聚物進行分子量的分析。共聚物加入去離子水和電解質(NaSCN、NaClO4和NaI)水溶液中，並改變電解質濃度及溶液的環境溫度，使用螢光探針法量測臨界微胞濃度，利用臨界微胞濃度的自然對數與電解質濃度的關係，計算其冪次關係中的指數n和微胞化熱力學參數，再以動態光散射儀(DLS)測量微胞粒徑。探討溫度、電解質濃度、電解質物種及高分子疏水鏈段聚合度對臨界微胞濃度、微胞化熱力學性質及微胞粒徑之影響。實驗結果發現臨界微胞濃度隨著溫度上升而增加，隨著疏水鏈段聚合度愈小而增加。當電解質(NaSCN和NaClO4)濃度增加時，臨界微胞濃度上升，而在NaI水溶液中，臨界微胞濃度隨著電解質濃度上升而下降。共聚物的疏水鏈段聚合度減小，造成臨界微胞濃度在電解質與純水中的比值越大，鹽析(salting)現象愈明顯，並發現臨界微胞濃度比值的自然對數與電解質濃度冪次關係中的指數值越小，NaSCN溶液中兩者的比值較NaClO4大，微胞化的電解質效應較明顯，指數值也越小。觀察臨界微胞濃度與疏水鏈段聚合度的關係後發現，溫度愈高，臨界微胞濃度與疏水鏈段聚合度冪次關係中的指數絕對值越小；電解質(NaSCN、NaClO4)濃度越高指數的絕對值越大，加入NaI後濃度越高指數絕對值越小。經由微胞化熱力學參數的計算結果得知，共聚物中PLLA鏈段聚合度愈小，微胞化自由能(負值)、微胞化焓(負值)和微胞化熵(正值)愈大。隨著電解質濃度(NaSCN和NaClO4)上升，微胞化自由能(負值)、微胞化焓(負值)和微胞化熵(正值)會增加。微胞化自由能為負值，表示共聚物在水溶液中的微胞化為自發性過程，且微胞化自由能、焓和熵受到NaSCN的影響較NaClO4明顯。隨著電解質(NaI)濃度上升，微胞化自由能下降，得知在salting-in現象中，微胞化自由能隨電解質濃度上升而增加，而在salting-out現象中兩者關係相反。平均微胞粒徑隨NaSCN濃度上升而減少，NaI濃度上升而增加；在NaI溶液中的粒徑變化量較NaSCN溶液中明顯。根據共聚物的微胞體積與微胞化自由能的線性關係，得知在兩類salting現象時形成微胞推動力越大微胞體積越大。根據結果微胞化自由能隨著電解質濃度的變化觀察到電解質加入共聚物溶液中發生salting-in或salting-out現象及會造成微胞體積的改變。

Methoxypoly(ethylene glycol)-Poly(L-lactide) (mPEG-PLLA) diblock copolymers with fixed mPEG length (degree of polymerization= 113) and various PLLA segment lengths (degree of polymerization= 168、35 and 301) were synthesized. The molecular weights of copolymers were analyzed by using gel permeation chromatography (GPC).
We use fluorescent probe to determine the critical micelle concentration (CMC) of diblock copolymer solutions with various concentrations of NaSCN , NaClO4 or NaI at 25 to 45℃,and calculate the power law exponents for the natural logarithm of CMC versus electrolytic concentration and thermodynamic parameters of micellization. The micelle size is also measured with dynamic light scattering (DLS). We research the effects of degree of polymerization, electrolyte species and concentrations on the CMC, thermodynamic properties of micellization and the particle size of micelles.Experimental results show that CMC increases with rising temperature, and increases with decreasing the degree of polymerization of hydrophobic block chains. The CMC are higher with the higher concentrations of electrolyte solutions(NaSCN and NaClO4). The CMC is lower with the higher concentrations of NaI solutions. The ratio of the CMC in the electrolyte solutions over in water is higher with decreasing the degree of polymerization of hydrophobic block chains, and the power law exponent for the natural logarithm of the ratio of the CMC in the electrolyte solutions over in water versus electrolyte concentrations is lower with decreasing the degree of polymerization of hydrophobic block chains. The ratio of the CMC in the NaSCN aqueous solutions over in water is higher than in NaClO4 aqueous solutions over in water, the power law exponent for the natural logarithm of the ratio of the CMC in the electrolyte solutions over in water versus electrolyte concentrations is lower in the NaSCN aqueous solutions than NaClO4 aqueous solutions. According to the power law exponents for CMC versus the degree of polymerization of hydrophobic segments, it is found that absolute values of exponents are lower with rising temperature. The absolute values of exponents are higher with the higher concentrations of electrolyte solutions(NaSCN and NaClO4). The absolute values of exponents are lower with the higher concentrations of NaI solutions.Calculated thermodynamic parameters of micellization show that the values of Gibbs energy of micellization (△Gmic, negative value), enthalpy of micellization (△Hmic, negative value) and entropy of micellization (△Smic, positive value) increase with decreasing the degree of polymerization of PLLA chains. The negative Gibbs energy indicates that micellization process is spontaneous. The values of △Gmic , △Hmic and △Smic increase with increasing concentrations of electrolyte solutions(NaSCN and NaClO4). The △Gmic 、△Hmic and △Smic are affected more significantly by NaSCN than NaClO4. The values of △Gmic decrease with increasing concentrations of NaI aqueous solutions, and the results show that in salting-in effect the values of △Gmic increase with increasing electrolyte concentrations, and in salting-out effect the values of △Gmic decrease with increasing electrolyte concentrations.The size of micelle decreases with increasing concentration of the NaSCN aqueous solutions, and increases with increasing concentration of the NaI aqueous solutions. The varitions of size with electrolyte concentrations in NaI aqueous solutions are more pronounced than in NaSCN aqueous solutions.According to the linear relationship between the micelle volume and the △Gmic, it is found that in salting effect the larger micelle volume is formed by larger micelle driving force. According to the variation of the △Gmic with electrolyte concentration,we observe the salting-in or salting-out effect in the copolymer solutions with electrolytes and it affects micelle volume.

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