Exploiting the Site Selectivity of Perfluoropyridine for Facile Access to Densified Polyarylene Networks for Carbon-Rich Materials

Abstract

Fluorinated molecules containing reactive functionalities are of great interest to the materials community as these compounds can be used to prepare fluorinated polymers with desirable physical and electronic properties. Despite their potential, many of these compounds are limited by their synthesis which generally requires transition-metal-catalyzed coupling reactions or harsh fluorinating conditions. Perfluoroheteroaromatic compounds provide a unique solution to this problem as compounds such as perfluoropyridine can undergo SNAr reactions with a wide range of simple nucleophiles in a controlled and regioselective manner. Herein we report the transition-metal-free synthesis of a pool of highly soluble high aromatic content (HAC) perfluoropyridine-based thermosetting precursors and compounds of interest which can be easily obtained from readily available chemical precursors using simple nucleophilic chemistries. These thermally active monomers cure readily, in 350–400 °C temperature ranges, into highly densified polyaryelene networks and demonstrate decomposition temperatures well above 400 °C and high char yields at 900 °C, making these promising materials for high-temperature applications as well as templates for carbon-based nanomaterials.

Perfluoropyridine: Discovery, Chemistry, and Applications in Polymers and Material Science

“…At around the same time, Houck et al reported the synthesis of two highly soluble high aromatic content (HAC) perflfluoropyridine-based thermosetting precursors [ 70 ]. Previously, to obtain polymers or materials that contain HAC, transition-metal-catalyzed coupling or harsh fluorination methods were required.…”

“…Initially, regioselective nucleophilic addition takes place with PFPy by first reacting it with lithiated 1,2-diphenylethyne or anthracene at the 4-position, to generate compounds 20 and 21 , respectively. To complete the monomers, further reactions are accomplished at both the 2 and 6-position by lithiated 1,2-diphenylethyne to generate monomers 22 and 23 , respectively ( Scheme 19 ) [ 70 ].…”

“…Upon curing 22 and 23 at 341 and 372 °C ( T max ), respectively, both systems yielded insoluble cross-linked networks. The cured network of 22 displayed an onset of decomposition ( T d ) of 470 °C and a char yield of 51% at 900 °C, while the cured network of 23 displayed a T d of 456 °C and a char yield of 81% at 900 °C ( Table 6 ) [ 70 ].…”

“…The ease of thermal setting, combined with the formation of rigid cross-linked networks of highly densified polyarylenes exhibiting high decomposition temperatures and high char yields indicate these thermoset polymers are promising templates for nanomaterials in microelectronics and for use in high-temperature applications in the aerospace industry [ 70 ].…”

“…Upon curing 22 and 23 at 341 and 372 °C (Tmax), respectively, both systems yielded insoluble cross-linked networks. The cured network of 22 displayed an onset of decomposition (Td) of 470 °C and a char yield of 51% at 900 °C, while the cured network of 23 displayed a Td of 456 °C and a char yield of 81% at 900 °C (Table 6) [70]. The ease of thermal setting, combined with the formation of rigid cross-linked networks of highly densified polyarylenes exhibiting high decomposition temperatures and high char yields indicate these thermoset polymers are promising templates for nanomaterials in microelectronics and for use in high-temperature applications in the aerospace industry [70].…”