Quasi-living polymerizations copolymers

Quasi-living Carbocationic Polymerization of Alkyl Vinyl Ethers and Block Copolymer Synthesis... 

The synthesis of PP-fr-EPR can be accomplished by a stopped-flow polymerization method, whose polymerization time is very short and which is a quasi-living system, in the presence of a MgCl2-supported titanium catalyst [132-135]. The results of GPC, 13C NMR, CFC, DSC, and optical microscopic observation indicated the formation of a block copolymer having a chemical linkage between PP and EPR segments. 

Quasi-living Carbocationic Polymerization Proton Traps Block Copolymers... 

Terminal ring functionalization has been explored as a route to block copolymer synthesis. The Stille coupling approach affords Br and RsSn termini on an isolable product. Iraqi and Barker isolated a low-A/ fraction (DP 14) then homo-cross-coupled to increase Af (DP ra 28), thus demonstrating telechelic utility [43]. The nature of the nickel-initiated cross-coupling polymerization (GRIM method) allows chain extension from the quasi-living end until the reaction is terminated. Controlled blocks of HT-PHT with HT-PDDT were prepared by changing the monomer [63]. 

Although living a-olefin polymerizations with transition metal catalysts are still quite rare despite the modem efficient examples recently developed (for a recent review, see [69]), some E—N copolymerizations have been shown to be quasi-living or living. The molecular mass of E-N copolymers by catalyst I-l, at temperatures between 30 and 50°C and high norbomene feed fi actions, increases with time for up to 1 h. The polydispersity can be as narrow as 1.1 at [N]/[E] = 28 [49], indicating that E—N copolymerizations are quasi-living under these conditions. 

The large variation in polymerization rates among the various 2-oxazoline monomers has been exploited for the preparation of quasi-diblock copolymers, namely, gradient copolymers with a narrow and steep monomer gradient, by statistical copolymerization of selected monomer combinations exhibiting large differences in reactivity. Such a one-pot quasi-diblock copolymer synthesis was first demonstrated for the statistical copolymerization of 2-phenyl-2-oxazoline and a much less reactive 2-perfluoroalkyl-2-oxazoline [174]. This living CROP (in nitromethane at 120 °C initiated by methyl p-nitrobenzenesulfonate) revealed complete consumption of the 2-phenyl-2-oxazoline after 2 min with only minor incorporation of the fluorinated monomer. Continuation of the polymerization for another 40 h led to full conversion of the fluorinated monomer. The... 

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