Low-temperature and purification-free stereocontrolled ring-opening polymerisation of lactide in supercritical carbon dioxide,Green Chemistry

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Low-temperature and purification-free stereocontrolled ring-opening polymerisation of lactide in supercritical carbon dioxide
Green Chemistry ( IF 9.3 ) Pub Date : 2020-03-11 , DOI: 10.1039/d0gc00352b
Simon P. Bassett _{1,

2,

3} , Andrew D. Russell _{3,

4,

5,

6} , Paul McKeown _{3,

4,

5,

6} , Isabel Robinson _{1,

2,

3} , Thomas R. Forder _{3,

4,

5,

6} , Vincenzo Taresco _{1,

2,

3} , Matthew G. Davidson _{3,

4,

5,

6} , Steven M. Howdle _{1,

2,

3}

Affiliation

A stereoselective, solvent-free ring-opening polymerisation (ROP) of lactide (LA) in supercritical carbon dioxide (scCO₂) is reported for the first time. The key aim is to exploit scCO₂ to lower the temperature of traditional melt polymerisations, lowering the energy requirement and leading to cleaner polymeric materials. We have utilised a zirconium amine-trisphenolate initiator-stereoselective catalyst [(ⁱPrO)Zr(OPh(^tBu)₂-CH₂)₃N] to yield highly heterotactic poly(lactide) (PLA) homopolymer (P_r = 0.74–0.84) from rac-LA, demonstrating control of the PLA microstructure in scCO₂. In addition, high monomer conversion (86–93%) was achieved in short reaction time (1 h), affording poly(lactide) with a very low degree of transesterification and narrow molecular weight distribution. Most importantly, all the reactions were performed at only 80 °C, almost 100 °C lower than the conventional melt process (typically performed at 130–180 °C), representing a very significant potential energy saving.

中文翻译：

丙交酯在超临界二氧化碳中的低温和无纯化立体控制的开环聚合

首次报道了丙交酯（LA）在超临界二氧化碳（scCO ₂）中的立体选择性，无溶剂的开环聚合（ROP）。关键目标是利用scCO ₂来降低传统熔融聚合的温度，降低能量需求并生产出更清洁的聚合物材料。我们利用锆胺-三酚盐引发剂-立体选择性催化剂[（ⁱ PrO）Zr（OPh（^t Bu）₂ -CH ₂）₃ N]生成高度杂规的聚（丙交酯）（PLA）均聚物（P _r = 0.74– 0.84）来自rac -LA，证明了对scCO _2中PLA微观结构的控制。此外，在短的反应时间（1小时）内实现了较高的单体转化率（86-93％），从而提供了具有非常低的酯交换度和窄分子量分布的聚（丙交酯）。最重要的是，所有反应都仅在80°C下进行，比传统的熔融工艺（通常在130–180°C下进行的反应）低了近100°C，这代表了非常显着的节能潜力。

更新日期：2020-04-24

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