Borane oxidation/polymerization mechanism

The peroxide 179 dissociates in the presence of a monomer giving rise to alkoxyl (CO-) and borinate (BO-) radicals, but the latter are believed to be too stable to initiate polymerization. It should be mentioned that the molecular weight continuously increases throughout the process implying the pseudo-living mechanism for chain growth. After the completion of the process borane residue is completely oxidized into diol <2004MM6260>. Thus, the 8-boraindane molecule not only initiates the polymerization, but also is a precursor to two functionalities in the polymer chain. 

Organometallic compounds asymmetric catalysis, 11, 255 chiral auxiliaries, 266 enantioselectivity, 255 see also specific compounds Organozinc chemistry, 260 amino alcohols, 261, 355 chirality amplification, 273 efficiency origins, 273 ligand acceleration, 260 molecular structures, 276 reaction mechanism, 269 transition state models, 264 turnover-limiting step, 271 Orthohydroxylation, naphthol, 230 Osmium, olefin dihydroxylation, 150 Oxametallacycle intermediates, 150, 152 Oxazaborolidines, 134 Oxazoline, 356 Oxidation amines, 155 olefins, 137, 150 reduction, 5 sulfides, 155 Oxidative addition, 5 amine isomerization, 111 hydrogen molecule, 16 Oxidative dimerization, chiral phenols, 287 Oximes, borane reduction, 135 Oxindole alkylation, 338 Oxiranes, enantioselective synthesis, 137, 289, 326, 333, 349, 361 Oxonium polymerization, 332 Oxo process, 162 Oxovanadium complexes, 220 Oxygenation, C—H bonds, 149... 

The combined information from oxidation adducts and the polymer chain end structure presents a complete picture of oxidation and the initiation mechanism of borane/oxygen-mediated radical polymerization of fluoromonomers at ambient temperature. This borane/oxygen initiator offers a safe and effective route to prepare fluoropolymers with high molecular weights and high purities. It also provides the control of polymer chain end structure by initiator. 

TrialkyIboranes and their oxidation products initiate polymerization of acrylic monomers as shown in Figure 5 (51-54). Complexes of tributyl borane with amines are more stable in air and can be easily reduced. With this initiator, polymer formation has been postulated to begin at the physiologically moist dentin surface. Grafting of the borane-cured resin to dentin may take place in the presence of moisture and bond strength is retained fairly well after water immersion. Bonding exists only between collagen of the dentin and any retention to enamel is of a mechanical nature. 

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