30-Apr-19
A new family of polymers that brings us closer to the dream of closed-loop, zero-waste plastics has been developed by team at the Lawrence Berkeley National Laboratory in California, USA. To achieve this they used a family of molecules called polydiketoenamines, held together by dynamic covalent bonds that, while very strong, can be easily broken down using small amounts of acid.
Diketoenamines were pretty much unknown in polymer chemistry until now. Lead author Brett Helms explains that ‘this motif had been known as a protecting group in solid state peptide chemistry, but often classified as “promiscuous” as it bounced around different amine groups during peptide synthesis. We thought that the promiscuity of diketoenamines was evidence of dynamic covalent behaviour, which could come in handy for synthesising new polymers,’ he explains. And it worked. Surprisingly, polydiketoenamines could be made simply by mixing ketones and amines. ‘It’s a click reaction that works at room temperature, without needing catalysts, additives or even a solvent,’ says Helms. ‘They just require a few minutes in a ball mill.’
‘While cleaning our glassware with acids, we realised that a chemical reaction was taking place,’ Helms says. ‘We decided to analyse the products, and we were dazed to identify our original monomers.’ Diketoenamines could be converted back to their building blocks using just concentrated acid.
解聚反应是实现可持续塑料回收目标的关键步骤。除此之外，擦除塑料以前的用途是从回收到升级的一种方法 - 从废物材料中创建更高的价值产品。赫尔斯和他的团队也实现了这一目标。他说：“我们可以将单体与制造商在其性能和美学（例如填充剂，着色剂或增塑剂）中塑料的所有额外成分分开。”O’Reilly说：“解聚单体和混合色添加剂之间的分离确实令人印象深刻。”“作者清楚地证明了技术的潜力。”
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