Tert-Butyl bromide polymerization

Imidazole or pyridine mediated silylation of l,2-0-[l-exo-ethoxy )ethylidene]-oc-D-glucopyranose failed to give a high yield of the 6-silyl ether due to some polymerization and side reactions. Activation of hydroxyl groups via a tributylstannyl intermediate followed by the tetrabutylammonium bromide catalyzed reaction with tert-butyl-chlorodiphenylsilane was more successful [231], the 6-0-silyl derivative being isolated in 87 % yield.. The lability of this protecting group under benzylation with benzyl bromide and sodium hydride at 0 °C has been observed [449]. 

ABC triblock copolymer is formed typically through sequential monomer addition in three ATRP steps. Step One polymerization of styrene (St) by mixing the components together in the following order - CuBr, St, PMDETA, and 1-phenyl ethyl bromide, typically at 100°C. The product is a monofunctional macroinitiator, namely, bromo-terminated polystyrene, P(St)-Br, which is isolated from the reaction products mixture and used in Step Two for the ATRP of tert-butyl acrylate (IBA) at 80°C, the order of addition of the components to the reaction mixture being P(St)-Br, CuBr, tBA, and PMDETA. The product of step 2 is a monofunctional, bromo-terminated macroinitiator, P(St)-l>-P(tBA)-Br, which is isolated from the reaction products mixture and used in Step Three for the synthesis of ABC triblock copolymer by ATRP of methyl acrylate (MA) at 70°C, the order of addition of the components to the reaction mixture being CuBr, P(St)-l>-P(tBA)-Br, MA, and PMDETA. The product of step 3 is the triblock copolymer P(St)-l>-P(tBA)-l>-P(MA)-Br. 

Acrylic acid cannot be polymerized by ATRP which is sensitive to the presence of acids. Moreover, since many of the ligand systems utilized are nitrogen-based, protonation of the nitrogen may occur, disrupting its coordination to the metal center. The solution to this problem is to polymerize protected monomers, followed by a deprotection step to generate the polyacid. Thus Davis and Matyjaszewski (2000) synthesized poly(acrylic acid) (PAA) via hydrolysis of poly(tert-butyl acrylate) (PrBA), which, in turn, was obtained by ATRP of iBA using a CuBr/PMDETA catalyst system in conjunction with an alkyl bromide, such as methyl-2-bromopropionate (MBrP), as the initiator. The monomer conversion was 93% after 320 min at 60°C. 

The 1,3-dipolar qrcloaddition reaction has also been used in grafting from approaches for the preparation of NT-polymer composites. In this respect, SWNTs were functionalized along their sidewalls with phenol groups, which were fiuilier derivatized with 2-bromoisobutyryl bromide, resulting in the attachment of ATRP initiators to the sidewalls of the nanotubes. These initiators were active in the polymerization of methyl methacrylate (MMA) and tert-butyl acrylate ( BA) from the surface of the NTs (Scheme 12.7) [57]. 

Other polymeric catalysts have also been investigated. Examples are seen in the supported oxime-based Hgands 54 [151d] and 55 [151e]. Both are active for the Heck reaction in water. The latter was shown to be efficient for the coupling of heterocychc aryl bromides with tert-butyl acrylate or styrene under thermal or MW heating [15 le]. 

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