Tian Jun-Jie, Liu Xiaoyang, Ye Liwei, Zhang Zhen, Quinn Ethan C, Shi Changxia, Broadbelt Linda J, Marks Tobin J, Chen Eugene Y-X
Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA.
Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA.
Angew Chem Int Ed Engl. 2024 Apr 22;63(17):e202320214. doi: 10.1002/anie.202320214. Epub 2024 Mar 15.
Geminal (gem-) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem-dimethyl groups onto ϵ-caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem-nylon 6's properties are highly sensitive to the substitution position, with the monomers ranging from non-polymerizable to polymerizable and the gem-nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with the gem-dimethyls substituted at the γ position is amorphous and optically transparent, with a higher T (by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6.
在杂环单体中进行偕二取代（gem-）是一种通过降低其最高聚合温度来提高聚合物化学可回收性的有效策略。然而，特定取代模式对单体反应性以及所得聚合物性能的影响在很大程度上尚未得到探索。在此我们表明，通过系统地将偕二甲基从α位到ε位安装到ε-己内酰胺（尼龙6的单体）上，重新设计的内酰胺单体的反应性以及所得偕尼龙6的性能对取代位置高度敏感，单体范围从不可聚合到可聚合，偕尼龙的性能范围从劣于到远优于母体尼龙6。值得注意的是，在γ位被偕二甲基取代的尼龙6是无定形且光学透明的，其玻璃化转变温度（高30 °C）、屈服应力（高1.5 MPa）、延展性（高3倍），并且解聚温度比传统尼龙6低（低60 °C）。
