Conventional metal-catalyzed organic radical reactions and living radical polymerizations (LRP) performed in nonpolar solvents, including atom-transfer radical polymerization (ATRP), proceed by an inner-sphere electron-transfer mechanism. One catalytic system frequently used in these polymerizations is based on Cu(I)X species and N-containing ligands. Here, it is reported that polar solvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2) species in the presence of a diversity of N-containing ligands. This disproportionation facilitates an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu(0) atomic species, while their deactivation is mediated by the nascent Cu(II)X(2) species. Both steps proceed by a low activation energy outer-sphere single-electron-transfer (SET) mechanism. The resulting SET-LRP process is activated by a catalytic amount of the electron-donor Cu(0), Cu(2)Se, Cu(2)Te, Cu(2)S, or Cu(2)O species, not by Cu(I)X. This process provides, at room temperature and below, an ultrafast synthesis of ultrahigh molecular weight polymers from functional monomers containing electron-withdrawing groups such as acrylates, methacrylates, and vinyl chloride, initiated with alkyl halides, sulfonyl halides, and N-halides.
ObjectiveSepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. In sepsis and septic shock, pathogen-associated molecular pattern molecules (PAMPS), such as bacterial exotoxins, cause direct cellular damage and/or trigger an immune response in the host often leading to excessive cytokine production, a maladaptive systemic inflammatory response syndrome response (SIRS), and tissue damage that releases DAMPs, such as activated complement and HMGB-1, into the bloodstream causing further organ injury. Cytokine reduction using extracorporeal blood filtration has been correlated with improvement in survival and clinical outcomes in experimental studies and clinical reports, but the ability of this technology to reduce a broader range of inflammatory mediators has not been well-described. This study quantifies the size-selective adsorption of a wide range of sepsis-related inflammatory bacterial and fungal PAMPs, DAMPs and cytokines, in a single compartment, in vitro whole blood recirculation system.Measurements and main resultsPurified proteins were added to whole blood at clinically relevant concentrations and recirculated through a device filled with CytoSorb® hemoadsorbent polymer beads (CytoSorbents Corporation, USA) or control (no bead) device in vitro. Except for the TNF-α trimer, hemoadsorption through porous polymer bead devices reduced the levels of a broad spectrum of cytokines, DAMPS, PAMPS and mycotoxins by more than 50 percent.ConclusionsThis study demonstrates that CytoSorb® hemoadsorbent polymer beads efficiently remove a broad spectrum of toxic PAMPS and DAMPS from blood providing an additional means of reducing the uncontrolled inflammatory cascade that contributes to a maladaptive SIRS response, organ dysfunction and death in patients with a broad range of life-threatening inflammatory conditions such as sepsis, toxic shock syndrome, necrotizing fasciitis, and other severe inflammatory conditions.
The mechanism of reductive cleavage of model alkyl halides (methyl 2-bromoisobutyrate, methyl 2-bromopropionate, and 1-bromo-1-chloroethane), used as initiators in living radical polymerization (LRP), has been investigated in acetonitrile using both experimental and computational methods. Both theoretical and experimental investigations have revealed that dissociative electron transfer to these alkyl halides proceeds exclusively via a concerted rather than stepwise manner. The reductive cleavage of all three alkyl halides requires a substantial activation barrier stemming mainly from the breaking C-X bond. The activation step during single electron transfer LRP (SET-LRP) was originally proposed to proceed via formation and decomposition of RX(•-) through an outer sphere electron transfer (OSET) process (Guliashvili, T.; Percec, V. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 1607). These radical anion intermediates were proposed to decompose via heterolytic rather than homolytic C-X bond dissociation. Here it is presented that injection of one electron into RX produces only a weakly associated charge-induced donor-acceptor type radical anion complex without any significant covalent σ type bond character between carbon-centered radical and associated anion leaving group. Therefore, neither homolytic nor heterolytic bond dissociation applies to the reductive cleavage of C-X in these alkyl halides inasmuch as a true radical anion does not form in the process. In addition, the whole mechanism of SET-LRP has to be revisited since it is based on presumed OSET involving intermediate RX(•-), which is shown here to be nonexistent.
Sodium dithionite in the presence of NaHCO 3 in water acts as a singleelectron-transfer agent and facilitates the single-electron-transfer/degenerative-chaintransfer mediated living radical polymerization (SET-DTLRP) of acrylates initiated with iodoform at room temperature. The resulting ␣,-di(iodo)polyacrylates can be used as macroinitiators for the SET-DTLRP of other acrylates. Ultrahigh-molar-mass poly-(tert-butyl acrylate) can be synthesized via the SET-DTLRP of tert-butyl acrylate and has a very low weight-average molecular weight/number-average molecular weight ratio of 1.15.
The new generation of catalytic systems for Controlled/"Living" Radical Polymerization (CLRP) of vinyl monomers should be non-toxic, inexpensive and provide fast polymerizations in environmentally friendly media. Herein, we report the successful ambient temperature ATRP of several vinyl monomers (MA, n-BA, MMA and DMAEMA) catalyzed by inorganic sulfites (Na S O and Na S O) and small amounts of a Cu(II)Br /Me TREN system in alcohol-water mixtures. The
Inorganic sulfites such as sodium dithionite (Na 2 S 2 O 4 ), sodium metabisulfite (Na 2 S 2 O 5 ), and sodium bisulfite (NaHSO 3 ) have been studied as reducing agents for atom transfer radical polymerization (ATRP). They act not only as very efficient reducing agents but also as supplemental activators for SARA (supplemental activator and reducing agent) ATRP of methyl acrylate in DMSO at ambient temperature. In combination with Cu(II)Br 2 /Me 6 TREN, they produced poly(methyl acrylate) with controlled molecular weight, low dispersity (M w /M n = 1.05), and well-defined chain-end functionality. Sulfites are eco-friendly, approved by FDA as food and beverage additives, and used commercially in many industrial processes.
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