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A novel one-pot methodology combining anionic polymerization and polyhomologation, through a ''bridge'' molecule (BF 3 OEt 2 ), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts with the ''bridge'' molecule to afford a 3-arm star (trimacromolecular borane) which serves as an initiator for the polyhomologation.Polyethylene (PE)-based materials are very important to modern life covering a wide spectrum of applications from commodity plastics (e.g. packaging, bottles) to precision-processed biomaterials (e.g. total joint replacement and medical devices).1 In order to better understand the behaviour and improve the performance of these materials, welldefined (controllable molecular weight, narrow molecular weight and structural distribution) PE-based polymers are needed. 2 Unfortunately, anionic polymerization which gives access to well-defined polymers when chain growth occurs in a ''living'' fashion is not compatible with ethylene, the monomer of PE. 3 The only way to prepare well-definedPEs by anionic polymerization is by hydrogenation of the corresponding anionically prepared PBd-1,4. However, the produced PE possesses butylene units originating from the hydrogenation of the unavoidable 1,2-units (minimum 5%) formed during the chain growth. 4 Recently, Shea developed a novel polymerization methodology leading to perfectly linear PEs. 5 The general reaction scheme involves the formation of an organoboron zwitterionic complex between a methylide (monomer) and a trialkylborane Lewis acid (initiator) which breaks down by the intramolecular 1,2-migration. As a consequence, the methylene group of methylide is randomly inserted one by one into the three branches of the trialkylborane leading to a 3-arm PE star. The resulting star is subsequently oxidized/hydrolysed to give perfectly OH-end-capped linear PEs. Molecular weights from 500 to 5.0 Â 10 5 and the polydispersity index (PDI) typically less than 1.1 have been reported. For this type of polymerization Shea coined the name polyhomologation or C1 polymerization. 5-7By using functionalized ylides and/or organoboranes, functionalized linear and nonlinear homo/copolymers, such as a-hydroxylo-allylic PE, 3-armed a-hydroxyl PE star, PE-co-PP(polypropylene) and cyclic PE have been synthesized. Here, we report a novel one-pot methodology combining anionic polymerization and polyhomologation, through a ''bridge'' molecule (BF 3 OEt 2 ), for the synthesis of polyethylene (PE)-based block copolymers. The synthetic approach involves: (a) the synthesis of a 3-arm star polymer (trimacromolecular borane, macroinitiator) by reacting living macroanions with BF 3 OEt 2 , (b) the in situ polyhomologation of dimethylsulfoxonium methylide, with the macroinitiator to produce a 3-arm star block copolymer of PE, and (c) the oxidation/hydrolysis by trimethylamine N-oxide dihydrate (TAO) to afford the PE-based block copolymers. As examples the syntheses of PBd-b-PE (PBd: polybutadiene) and PS-b-PE are shown in Scheme...

Polyhomologation, recently developed by Shea, is a borane-initiated living polymerization of ylides leading to linear polymethylenes (C1 polymerization) with controlled molecular weight, low polydispersity, and well-defined structures. In this Review, the copolyhomologation of different ylides as well as the combination of polyhomologation with controlled/living (nitroxide-mediated, atom transfer radical, reversible addition-fragmentation chain-transfer) and living (ring opening, anionic) polymerizations is discussed.

ARTICLE This journal isA novel strategy towards well-defined polymethylene-based co/terpolymers, by combining anthracene/maleimide Diels-Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: a) synthesis of α-anthracene-ω-hydroxypolymethylene by polyhomologation using tri (9-anthracene-methyl propyl ether) borane as initiator, b) synthesis of furan-protected-maleimide-terminated poly (ε-caprolactone) or polyethylene glycol and c). Diels-Alder reaction between the anthracene and maleimide-terminated polymers. In the case of triblock terpolymers the α-anthracene-ω-hydroxy-polymethylene was used as macroinitiator for the ringopening polymerization of D, L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by Diels-Alder reaction with furan-protected maleimide-terminated poly (ε-caprolactone) or polyethylene glycol to give the triblock terpolymers. All intermediate and final products were characterized by SEC, 1 H NMR, UV-VIS spectroscopy and DSC.