The developing urea class of H-bond donors facilitates the solvent-free ROP of lactones at ambient and elevated temperatures, displaying enhanced rates and control versus other known organocatalysts for ROP under solvent-free conditions. The ROPs retain the characteristics of living polymerizations despite solidifying prior to full conversion, and copolymers can be accessed in a variety of architectures. One-pot block copolymerizations of lactide and valerolactone, which had previously been inaccessible in solution phase organocatalytic ROP, can be achieved under these reaction conditions, and one-pot triblock copolymers are also synthesized. For the ROP of lactide, however, thioureas remain the more effective H-bond donating class. For all (thio)urea catalysts under solvent-free conditions and in solution, the more active catalysts are generally more controlled. A rationale for these observations is proposed. The triclocarban (TCC) plus base systems are particularly attractive in the context of solvent-free ROP due to their commercial availability which could facilitate the adoption of these catalysts.

中文翻译：

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用于内酯的无溶剂开环聚合的H键有机催化剂：迈向全内酯，所有条件的方法

发展中的脲类氢键供体有助于在环境温度和高温下实现内酯的无溶剂ROP，与其他已知的无溶剂条件下ROP的有机催化剂相比，显示出更高的速率和控制能力。尽管在完全转化之前已固化，但ROP仍保留了活性聚合反应的特性，并且可以采用多种结构访问共聚物。在这些反应条件下，可以实现以前无法在溶液相有机催化ROP中实现的丙交酯和戊内酯的一锅嵌段共聚，并且还可以合成一锅三嵌段共聚物。但是，对于丙交酯的ROP，硫脲仍然是更有效的H键捐赠类。对于所有在无溶剂条件下和溶液中的（硫）脲催化剂，活性较高的催化剂通常受到更严格的控制。提出了这些观察的理由。在无溶剂的ROP方面，三氯卡班（TCC）加碱系统特别具有吸引力，因为它们具有商业用途，可以促进这些催化剂的采用。