This study provides experimental cloud point data for poly(D,L-lactic acid) (PDLLA) polymer and supercritical solvent and cosolvent mixtures at ~333K to ~424K and pressures up to ~157MPa for PDLLA. Various solvents investigated include CO, DME, CHF, CHF, CF, CH, c-CF, and F-22. CO is a preferred solvent due to non-toxic, non-flammability, low cost but the results indicate low PDLLA solubility in CO at ~100 to 110MPa and at experimental temperature range of 333.15K to 423.15K. However, for DME and F-22 solvents, the cloud points appear at ~10 to 30MPa suggesting these are better suited to dissolve polymers for supercritical processes. The results indicate that DME is the favored solvent due to its superior performance. In the pure component system, the cloud point curve exhibited a distinctive nature, displaying behaviors such as UCST, horizontal, or LCST under the experimental conditions. However, the phase behavior of PDLLA in the presence of both solvent and co-solvent demonstrated a transition from UCST to LCST types. This observed change suggests variations in the solubility of the polymer under the same experimental conditions, highlighting the dynamic influence of co-solvents on PDLLA's solubility characteristics. For systems with higher molecular weight PDLLA, increased self-association resulted in reduced solubility and upward shift of cloud point curves. This study will be helpful in optimizing solvent + cosolvent and operating conditions involving PDLLA in supercritical processes, especially in biomedical applications.

中文翻译：

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超临界溶剂下三元和二元溶液共溶剂浓度对可生物降解聚(D,L-乳酸)的影响

本研究提供了聚(D,L-乳酸) (PDLLA) 聚合物以及超临界溶剂和助溶剂混合物在 ~333K 至 ~424K 以及 PDLLA 压力高达 ~157MPa 下的实验浊点数据。研究的各种溶剂包括 CO、DME、CHF、CHF、CF、CH、c-CF 和 F-22。CO 由于无毒、不易燃、成本低而成为优选溶剂，但结果表明 PDLLA 在约 100 至 110MPa 和实验温度范围 333.15K 至 423.15K 的 CO 中溶解度较低。然而，对于 DME 和 F-22 溶剂，浊点出现在约 10 至 30MPa 之间，表明这些溶剂更适合溶解超临界工艺的聚合物。结果表明，DME 因其优越的性能而成为最受欢迎的溶剂。在纯组分体系中，浊点曲线表现出独特的性质，在实验条件下表现出 UCST、水平或 LCST 等行为。然而，在溶剂和共溶剂存在下，PDLLA 的相行为表现出从 UCST 类型到 LCST 类型的转变。这种观察到的变化表明在相同的实验条件下聚合物的溶解度存在变化，突出了共溶剂对 PDLLA 溶解度特性的动态影响。对于具有较高分子量 PDLLA 的系统，自缔合增加导致溶解度降低和浊点曲线向上移动。这项研究将有助于优化超临界工艺中涉及 PDLLA 的溶剂+助溶剂和操作条件，特别是在生物医学应用中。