Synthesis and properties of cycloaliphatic diepoxides containing fluorinated linker

Abstract

Abstract Cycloaliphatic diepoxides, CAEs, are well known for their better thermal, chemical and optical properties, compared with the glycidyl ether type epoxides. However, the shortages including low moisture resistance, and high reflective index or high dielectric constant limit their use for the emerging advanced optical and electronic applications, In this work, we have synthesized two new cycloaliphatic diepoxides containing different fluorinated linkers (2,2′‐((2,2,3,3‐tetrafluorobutane‐1,4‐diyl)bis(oxy))bis(7‐oxabicyclo[4.1.0]heptane) (TCE) and 2,2′‐((2,2,3,3,4,4,5,5‐octafluorohexane‐1,6‐diyl)bis(oxy))bis(7‐oxabicyclo[4.1.0]heptane) (OCE) and characterized their chemical structures using 1 H NMR, 19 F NMR, and Fourier transform infrared spectroscopy. We have cured these two fluorine‐containing CAEs, using hexahydro‐4‐methylphthalic anhydride (HMPA) and compared them with a commercial CAE, 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexanecarboxylate (ERL‐4221) under the same condition. Compared to the cured ERL‐4221 (C‐ERL‐4221), the cured fluorinated CAEs (C‐OCE, C‐TCE) have much better water resistances (saturated water absorption after 6 days in water: 0.70%, 1.72%, and 2.83%, for C‐OCE, C‐TCE, and C‐ERL‐4221, respectively) and lower dielectric constant ( D k ) ( D k : 2.54–2.44 and 2.78–2.66 vs. 4.01–4.00 @ 1 Hz‐5 MHz), and similar thermal stability (the statistical heat‐resistant index [ T s ]: 169°C, 175°C vs. 175.5°C), although their glass transition temperature ( T g ) and storage moduli are lower ( T g : 136°C, 171°C vs. 250°C; moduli: 0.56GPa, 1.25GPa vs. 1.38GPa). These results reveal that fluorine atoms on the linkers effectively reduce dielectric constant and improve hydrophobicity and wettability, providing new insights into the design of fluorine‐containing cycloaliphatic diepoxides.