From the standpoint of green chemistry, tris(pentafluorophenyl)gallium (7) and tris(pentafluorophenyl) aluminum ( 8) outperform all previously explored perfluoroarylated Lewis acids (PFLAs) for the polymerization of isobutene. In comparison to other PFLA based systems, 7 and 8 do not require ultrahigh purity monomer, toxic chlorinated solvents, or expensive and highly sensitive initiators (e.g., metallocenes). Moreover, compared to other PFLA based initiator systems they provide much larger yields of high to medium molecular weight polyisobutene even at polymerization temperatures up to ambient. Stopping experiments indicate that strong Brønsted acids formed in situ by reaction with adventitious moisture (9 and 10, respectively) induce cationic polymerization protonically. Unlike other PFLA compounds which require expensive and/or energetically unstable precursors, 7 and 8 are readily synthesized from their corresponding group 13 halides in conjunction with bis(pentafluorophenyl)zinc ( 6), thereby lending themselves to commercial implementation.
The purpose of this study was to contribute to the body of literature regarding decisions school leaders make when developing strategic plans to improve student outcomes. This study investigated whether there is a significant relationship between school climate and graduation rates for public high schools in the state of Georgia when controlling for potential covariates. Using an ordinary least squares multiple regression procedure, this study found a positive school climate increased high school graduation rates ( b = .164, p ≤ .01).
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