During the fabrication of poly(lactide-co-glycolic acid) (PLGA) microspheres by the water/oil/water (W₁/O/W₂) emulsion solvent evaporation method, water permeation coupled with dichloromethane (DCM) volatilization represents a critical process affecting the microsphere morphology. In this work, the mechanism of pore formation in PLGA through water permeation has been verified. By molecular simulations, the diffusion coefficients of water with different DCM contents were determined. The results showed that the diffusion coefficient decreased rapidly from 53.33 × 10^–6 to 6.73 × 10^–6 cm²/s after decreasing the DCM mass fraction from 94 to 63%. Furthermore, the higher stirring speed and lower volume of the external aqueous phase promoted the DCM volatilization. Two different mass transfer stages were identified for water permeation, and the first stage could be considered the main mass transfer window because of its high diffusion coefficient. The morphology of PLGA microspheres confirmed the existence of a relationship between water permeation and DCM volatilization.

中文翻译：

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通过双乳化法了解溶剂蒸发对 PLGA 微球形态的影响

在通过水/油/水 (W ₁ /O/W ₂ ) 乳液溶剂蒸发法制备聚（丙交酯 -共- 乙醇酸）（PLGA）微球期间，水渗透与二氯甲烷（DCM）挥发代表了关键影响微球形态的过程。在这项工作中，已经验证了PLGA中通过水渗透形成孔的机制。通过分子模拟，确定了不同DCM含量的水的扩散系数。结果表明，扩散系数从 53.33 × 10 ^–6迅速下降到 6.73 × 10 ^–6 cm ²/s 在将 DCM 质量分数从 94% 降低到 63% 之后。此外，较高的搅拌速度和较低的外部水相体积促进了 DCM 的挥发。确定了水渗透的两个不同传质阶段，第一阶段由于其高扩散系数可以被认为是主要的传质窗口。PLGA 微球的形态证实了水渗透和 DCM 挥发之间存在关系。