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Effects of supercritical carbon dioxide treatment on the morphology of poly(l-lactide)

机译：超临界二氧化碳处理对聚丙交酯形态的影响

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摘要

Synthetic l-lactide random copolymers can be employed as controlled release materials when prepared using supercritical carbon dioxide (scCO(2)), since they are biodegradable via hydrolysis. To determine the effects of thermal properties on polymer performance following scCO(2) processing, three types of poly(l-lactide) having different properties were assessed. The T-m of one poly(l-lactide) sample (H-100) was found to be approximately 170 degrees C over the processing pressure range from 8 to 18 MPa, while a second sample (H-440) also showed a constant value of approximately 152 degrees C. In contrast, the poly(l-lactide) REVODE exhibited a T-m of 146 degrees C prior to processing but a higher value of 147 degrees C following treatment at 8 MPa. Unlike the H-100 and H-440, the T-m value of the REVODE tended to decrease with increasing pressure. The T-g values increased greatly under mild conditions of 8 MPa pressure and a temperature of 40 degrees C. In particular, the T-g values for the H-440 and REVODE increased by 4 degrees C and 5 degrees C, respectively. All T-g values were lowest at 12 MPa and increased with increasing processing pressure, although the effect of processing temperature was minimal. The (cDSC) of the H-100 was 18% initially but increased to 20% upon scCO(2) processing at 40 degrees C and 14 MPa, and showed further increases at higher processing temperatures. Although the relationship between processing temperature and (cDSC) values for the H-440 showed the same trend as observed with the H-100, a different trend was seen for the REVODE. The (cXRD) values obtained from the XRD analyses differed from the values generated by DSC analysis, and showed a maximum degree of crystallinity following processing at 80 degrees C both with and without scCO(2) treatment. ATR FT-IR analyses identified peaks due to semicrystalline regions in poly(l-lactide) samples treated with scCO(2), even when applying low temperatures. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44006.
机译：使用超临界二氧化碳（scCO（2））制备时，合成的l-丙交酯无规共聚物可用作控释材料，因为它们可通过水解生物降解。为了确定scCO（2）处理后热性能对聚合物性能的影响，评估了三种具有不同性能的聚（1-丙交酯）。发现一个聚（l-丙交酯）样品（H-100）的Tm在8至18 MPa的处理压力范围内约为170摄氏度，而第二个样品（H-440）的Tm也保持恒定。约152℃。相反，聚（1-丙交酯）REVODE在加工前表现出146℃的Tm，但是在8MPa下处理后表现出更高的147℃的Tm。与H-100和H-440不同，REVODE的T-m值会随着压力的增加而降低。在温度为8 MPa和温度为40摄氏度的温和条件下，T-g值大大增加。特别是，H-440和REVODE的T-g值分别增加了4摄氏度和5摄氏度。尽管加工温度的影响最小，但所有T-g值在12 MPa时最低，并随加工压力的增加而增加。 H-100的（cDSC）最初为18％，但在40℃和14 MPa的scCO（2）处理下会增加到20％，并且在更高的处理温度下会进一步增加。尽管H-440的加工温度和（cDSC）值之间的关系显示出与H-100相同的趋势，但REVODE却看到了不同的趋势。从XRD分析获得的（cXRD）值与DSC分析生成的值不同，并且在经过和未经过scCO（2）处理的情况下，在80°C的处理下均显示出最大的结晶度。 ATR FT-IR分析确定了峰，该峰归因于用scCO（2）处理的聚（1-丙交酯）样品中的半结晶区域，即使在低温下也是如此。 （c）2016 Wiley Periodicals，Inc. J. Appl。 Polym。科学2016，133，44006。

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