A nanoporous epoxy film was formulated by using chemically modified epoxide-terminated polypropylene carbonate (ePPC) as the porogen in an epoxy resin formulation. The ePPC was grafted onto styrene maleic anhydride (SMA) copolymer and further used to chemically crosslink with poly(bisphenol A diglycidyl ether) (pBPADGE). The SMA-pBPADGE crosslinking was initiated with a tertiary amine catalyst. After curing of the pBPADGE resin film, the ePPC was thermally decomposed and created volatile, small molecules that diffused through the film leaving a nanoporous epoxy film. The pore size distribution within the epoxy film with ePPC loadings of 5 to 20 wt% after thermal degradation of the porogen was mostly between 6 to 18 nm as measured by nitrogen absorption experiments. The dielectric constant of the resulting 20% porous epoxy film was 2.77 and dielectric loss of 0.015. Mechanical properties and glass transition temperature of the cured film decreased slightly compared to the same film without pores. The reduced modulus of the epoxy film with 20% pore volume was 8 GPa and the glass transition temperature of 142 • C.
Epoxide functionalized poly(propylene carbonate) (ePPC) was included in an epoxy resin formulation and thermally decomposed to create nanoporous epoxy film. The dielectric constant of the porous epoxy was lower than the epoxy formulation control. The introduction of 30% porosity in the epoxy lowered the dielectric constant from 3.78 to 2.76. A postporosity chemical treatment further lowered the dielectric constant. Hexamethyldisilazane (HMDS) was used to terminate the pore walls with the hydrophobic silane layer and reduce both the dielectric constant and tangent loss of the porous epoxy. Two different styrene maleic anhydride crosslinking agents were used in the epoxy formulation, styrene maleic anhydride 2000 (SMA2000) and styrene maleic anhydride 4000 (SMA4000). The effect of the maleic anhydride concentration within SMA on the electrical, mechanical, and thermal properties of porous epoxy film was evaluated. Epoxy films crosslinked with SMA2000 resulted in films with a higher dielectric constant compared to films prepared with SMA4000 due to higher mole fraction of maleic anhydride within SMA2000. However, SMA2000 crosslinked films yielded films with better mechanical and thermal properties. SMA2000 crosslinked films with 30% porosity had a coefficient of thermal expansion (CTE) of 35.2 ppm/K and glass transition temperature of 143 °C.
Inherently disordered structures of carbon nitrides have hindered an atomic level tunability and understanding of their catalytic reactivity. Herein, coordination of copper cations within a crystalline carbon nitride, i.e., poly(triazine imide) or CNx, was found to yield two ordered structures for Cu-CNx wherein one or two Cu(I) cations coordinate to its intralayer N-triazine groups. The crystallites electrophoretically deposit from aqueous particle suspensions and yield current densities of ~10 to 50 mA/cm2 with a concomitant and increasing reduction of CO2 and H2O. Reduction of CO2 increases for smaller particles as mechanistic calculations reveal its catalysis mediated by two intralayer Cu atoms.
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