Hu Yixin, Wang Liqi, Kevlishvili Ilia, Wang Shu, Chiou Chun-Yu, Shieh Peyton, Lin Yangju, Kulik Heather J, Johnson Jeremiah A, Craig Stephen L
Department of Chemistry, Duke University, Durham, North Carolina 27705, United States.
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
J Am Chem Soc. 2024 Apr 10;146(14):10115-10123. doi: 10.1021/jacs.4c01402. Epub 2024 Mar 30.
Hydrogen fluoride (HF) is a versatile reagent for material transformation, with applications in self-immolative polymers, remodeled siloxanes, and degradable polymers. The responsive generation of HF in materials therefore holds promise for new classes of adaptive material systems. Here, we report the mechanochemically coupled generation of HF from alkoxy--difluorocyclopropane (DFC) mechanophores derived from the addition of difluorocarbene to enol ethers. Production of HF involves an initial mechanochemically assisted rearrangement of DFC mechanophore to α-fluoro allyl ether whose regiochemistry involves preferential migration of fluoride to the alkoxy-substituted carbon, and ab initio steered molecular dynamics simulations reproduce the observed selectivity and offer insights into the mechanism. When the alkoxy DFC mechanophore is derived from poly(dihydrofuran), the α-fluoro allyl ether undergoes subsequent hydrolysis to generate 1 equiv of HF and cleave the polymer chain. The hydrolysis is accelerated via acid catalysis, leading to self-amplifying HF generation and concomitant polymer degradation. The mechanically generated HF can be used in combination with fluoride indicators to generate an optical response and to degrade polybutadiene with embedded HF-cleavable silyl ethers (11 mol %). The alkoxy-DFC mechanophore thus provides a mechanically coupled mechanism of releasing HF for polymer remodeling pathways that complements previous thermally driven mechanisms.
氟化氢（HF）是一种用于材料转化的多功能试剂，可应用于自牺牲聚合物、重塑硅氧烷和可降解聚合物。因此，材料中HF的响应性生成有望用于新型自适应材料系统。在此，我们报告了由二氟卡宾加成到烯醇醚衍生的烷氧基二氟环丙烷（DFC）机械力发色团通过机械化学耦合生成HF的过程。HF的生成涉及DFC机械力发色团最初的机械化学辅助重排为α-氟代烯丙基醚，其区域化学涉及氟优先迁移到烷氧基取代的碳上，并且从头算引导的分子动力学模拟再现了观察到的选择性并提供了对该机制的见解。当烷氧基DFC机械力发色团衍生自聚（二氢呋喃）时，α-氟代烯丙基醚随后发生水解，生成1当量的HF并裂解聚合物链。水解通过酸催化加速，导致HF的自放大生成和聚合物的伴随降解。机械产生的HF可与氟化物指示剂结合使用，以产生光学响应，并降解含有HF可裂解硅醚（11摩尔%）的聚丁二烯。因此，烷氧基-DFC机械力发色团为聚合物重塑途径提供了一种机械耦合释放HF的机制，这补充了先前的热驱动机制。
