本研究主要目的為利用電漿改質聚乳酸-聚甘醇酸共聚物(PLGA)，觀察表面性質對體外降解實驗的影響；藉由溶劑揮發法製成PLGA薄膜，並經由氧氣電漿及氧氣/六氟化硫電漿分別進行單面及雙面改質。將改質後的PLGA樣品置於磷酸鹽緩衝溶液中，控制溫度在37℃，進行體外降解實驗。實驗分成兩組進行：其中，第ㄧ組降解實驗中，不更換PBS，亦即不控制酸鹼值，在第二組降解實驗中，則將體外降解環境之酸鹼值控制在7~7.4之間，觀察PLGA降解情形。
由第ㄧ組實驗結果得知，未經電漿改質之PLGA降解速率最快；第二組實驗結果發現，電漿單面改質之PLGA樣品的降解速率與未改質之樣品的降解速率相當，而電漿氧氣雙面改質之PLGA具有最快的降解速率。再者，利用凝膠滲透層析儀(GPC)、熱重分析儀(TGA)及示差掃描量熱儀(DSC)分析，詳細探討PLGA降解之情形。由GPC結果發現，降解反應初期，會造成分子量的下降，但PLGA並沒有重量損失的情形；當降解時間變長，PLGA會有明顯的重量損失變化，且分子量也持續地減少。PLGA進行降解反應時，高分子材料會產生裂解而造成重量損失及分子量的改變，進而影響材料之熱性質的變化。利用TGA及DSC分析結果得知，降解反應後之PLGA分子量變少，導致熱裂解溫度及玻璃轉移溫度較低；隨著降解時間的增加，PLGA之熱裂解溫度與玻璃轉移溫度會呈逐漸遞減的狀態。

The goal of this work is to investigate the effects of surface hydrophilicity on the in vitro degradation of poly(DL-lactide-co-glycolide) (PLGA) by applying oxygen and sulfur hexafluoride (SF6) plasmas.. The PLGA films were fabricated by solvent evaporation technique and treated by plasmas for one-side and double-side, with or without pH control for the PLGA immersed solution. The experimental results showed that, for the non-pH controlled PLGA, the highest degradation rate is possessed by non plasma-treated PLGA film (control). On the other hand, for the controlled pH PLGA samples, higher degradation rate is achieved by double-side O2-plasma-treated PLGA film.
The degradation characteristics are analyzed by gel permeation chromatography (GPC), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). GPC results showed that, in the beginning phase of the degradation, the molecular weight decreases while the weight loss seems to be unaffected. Progressively, mature phase of degradation took place, resulting in increasing rate of weight loss. During this phase, the PLGA films suffered swelling, cracking, and hydrolysis which change their thermal properties. The thermal decomposition temperature (by TGA measurement) and glass transition temperature (DSC) decrease also in this phase.
In summary, the effect of plasma treatment on PLGA degradation is not significant enough to alter the degradation rate which indicates that the plasma modification only limits on the very top layer of surface (about 10 ~ 1000Å.) of materials. According to the experimental results, we conclude that the degradation mechanism is closely related to water uptake, molecular weight loss and change in thermal properties of PLGA.

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