Two-dimensional covalent organic frameworks (2D-COFs) have been of increasing interest in the past decade due to their porous structures that ideally can be highly ordered. One of the most common routes to these polymers relies on Schiff-base chemistry, i.e., the condensation reaction between a carbonyl and an amine. In this report, we elaborate on the condensation of 3,6-dibromobenzene-1,2,4,5-tetraamine with hexaketocyclohexane (HKH) and the subsequent carbonylation of the resulting COF, along with the possibility that the condensation reaction on HKH can result in a trans configuration resulting in the formation of a disordered 2D-COF. This strategy enables modification of COFs via bromine substitution reactions to place functional groups within the pores of the materials. Ion-sieving measurements using membranes from this COF, reaction of small molecules with unreacted keto groups along with modeling studies indicate disorder in the COF polymerization process. We also present a Monte Carlo simulation that demonstrates the influence of even small amounts of disorder upon both the 2D and 3D structure of the resulting COF.
This investigation covers the use of the dimethyl silicone polymer fluids and methyl phenyl copolymers at elevated temperatures. A specially designed small-bearing machine was used at bearing temperatures of 325 F to 500 F and at ambient or plate temperatures as high as 650 F. Hard chromium-plated journals were used in conjunction with bearings of 89 per cent copper, 4 per cent tin and 4 per cent lead, and 3 per cent zinc alloy. Loads up to 8500 psi were carried at 425 to 500 F, and loads up to 13,000 psi at 180 to 200 F, using the dimethyl silicone fluid. Comparisons are made of the lubricating characteristics of the two classes of silicone fluids investigated. For satisfactory operation, either a long break-in or a silicone pretreatment of the bearings is desirable. Data on safe operating temperatures and rates of increase of viscosity are presented.
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