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首页> 外文期刊>RSC Advances >Continuous cyclo-polymerisation of L-lactide by reactive extrusion using atoxic metal-based catalysts: easy access to well-defined polylactide macrocycles
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Continuous cyclo-polymerisation of L-lactide by reactive extrusion using atoxic metal-based catalysts: easy access to well-defined polylactide macrocycles

机译：使用无毒金属基催化剂通过反应挤出连续进行L-丙交酯的环聚合反应：轻松获得定义明确的聚丙交酯大环化合物

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摘要

The bulk polymerisation of L-lactide was assessed using the alkaline-earth and lanthanide borohydride complexes Mg(BH4)(2) (1), Ca(BH4)(2)(THF)(2) (2) and Ln(BH4)(3)(THF)(3) with Ln = Nd (3), Sm (4) and La (5). All five catalysts display good activities, with up to 77% conversion in 20 min with 5. Lanthanide-based catalysts 3, 4 and 5, which were found to lead to the highest conversions, were tested in reactive extrusion polymerisation conditions in a twin-screw micro-extruder. High activities were also observed in theses experimental conditions, affording up to 73% conversion in only 20 min with lanthanum-based catalyst 5. More interestingly, the polylactides formed display a macrocyclic structure with molecular weights up to 30 000 g mol(-1) along with relatively narrow dispersities (1.23-1.79). The macrocycles are formed via intramolecular transesterification reactions taking place during the ring opening polymerisation. Furthermore, the reactive extrusion polymerisations operate at a temperature as low as 130 degrees C, this monomer usually being polymerized at 185 degrees C. This is the first example of a cyclic polyester obtained directly via a continuous process.
机译：使用碱土和镧系元素硼氢化物配合物Mg（BH4）（2）（1），Ca（BH4）（2）（THF）（2）（2）和Ln（BH4）评估L-丙交酯的本体聚合（3）（THF）（3），其中Ln = Nd（3），Sm（4）和La（5）。所有五种催化剂均显示出良好的活性，在5分钟内用5可以在20分钟内达到77％的转化率。在反应挤出聚合条件下，在双反应塔中对镧系元素3、4和5的转化率进行了测试。螺杆微型挤出机。在这些实验条件下也观察到高活性，使用镧基催化剂5在短短20分钟内可提供高达73％的转化率。更有趣的是，所形成的聚丙交酯显示出分子量高达30 000 g mol（-1）的大环结构。以及相对较窄的分散度（1.23-1.79）。大环通过开环聚合过程中发生的分子内酯交换反应形成。此外，反应性挤出聚合在低至130℃的温度下操作，该单体通常在185℃下聚合。这是直接通过连续方法获得的环状聚酯的第一个实例。

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