AbstractA living topochemical ring‐opening polymerization (ROP) of achiral amino‐acid N‐carboxyanhydrides (NCAs) is reported. Single crystals of the NCAs of α‐aminoisobutyric acid (Aib) and 1‐aminocyclohexanecarboxylic acid (ACHC) were grown, allowing a ring‐opening polymerization macroscopically induced by amines. The single crystals could be polymerized at temperatures from 25–50 °C after physically contacting the amine‐based initiator with the crystals. Topochemical polymerization of the crystals was proven by MALDI‐ToF MS and XRD, generating polymers with chain lengths of up to 40 units and a complete affixation of the initiating amine at the polymer's head. Due to the proper alignment of the reacting groups in the crystal, longer polymer chains with improved purities can be reached, as chain‐transfer is reduced as compared to solution polymerization. Simple purification of the polymers can be achieved by separation of the unreacted NCA via dispersion in acetonitrile. Overall, this method enables the preparation of polymers with higher chain length and purities at mild conditions, finally demonstrating a crystal‐based ring opening polymerization.
摘要 报告了非手性氨基酸 N-羧基酸酐(NCAs)的活拓扑化学开环聚合(ROP)。α-氨基异丁酸(Aib)和 1-氨基环己烷羧酸(ACHC)的 NCAs 单晶被生长出来,在胺的宏观诱导下实现了开环聚合。将胺类引发剂与单晶体物理接触后,单晶体可在 25-50 °C 的温度下聚合。MALDI-ToF MS 和 XRD 证实了晶体的拓扑化学聚合反应,生成的聚合物链长可达 40 个单位,并且引发胺完全附着在聚合物的头部。由于反应基团在晶体中的正确排列,与溶液聚合相比,链转移减少,因此可以得到更长的聚合物链,纯度也得到提高。通过在乙腈中分散分离未反应的 NCA,可实现聚合物的简单纯化。总之,这种方法能够在温和的条件下制备出链长和纯度更高的聚合物,最终证明了基于晶体的开环聚合。