Very few 6-vinylfulvenes have previously been reported in the literature. In a few cases where Little's procedure (using pyrrolidine as base) has been employed, most enones undergo conjugate attack by the cyclopentadienyl anion followed by either a retroaldol reaction or dihydropentalene formation. In several cases, Diels-Alder reaction of the enone with cyclopentadiene occurs rather than condensation. We have found that in cases where the Little procedure fails to give the desired 6-vinylfulvenes, the Thiele method using NaOH (or NaOMe in some cases) as base gives satisfactory results. In the latter instances, Michael attack is completely suppressed in all but one example. By appropriate choice of base, a variety of fulvenes carrying functional groups on the 6-alkyl position can be prepared. Some of these fulvenes have been shown to undergo further functional group transformations (e.g., nucleophilic substitutions), giving rise to derivatives bearing SR, S(0)R, N3, or SCN groups.
In this article, the morphology, particle size, and plugging properties of crosslinked polyacrylamide (CPAM) microspheres were investigated through optical microscopy, scanning electron microscopy (SEM), nuclear-pore membrane filtration experiments, a micro-visual model, sandpack experiments, parallel twin-tube plugging, and oil displacement experiments. The results revealed that the primary particle sizes of the CPAM microspheres ranged from several hundreds of nanometers to 5 lm; however, after the microspheres were fully swelled in water, their sizes increased by approximately five times of their original sizes. As a CPAM microsphere dispersion system had good dispersibility and deformation capabilities, a 1.2 lm nuclear-pore membrane as well as the deep part of a sandpack tube could be effectively plugged. Consequently, the flow diversion effect was achieved in the vertical and planar directions. When the CPAM microspheres migrated in porous media, they could displace residual oil on the pole wall and water flow channel to realize the synchronization of profile control and coordination and improve recovery efficiency. V C 2016 Wiley Periodicals, Inc. J. Appl.Polym. Sci. 2016, 133, 43666.
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