Facile and efficient bromination of hydroxyl-containing polymers to synthesize well-defined brominated polymers

This article demonstrates a new post-modification method to synthesize well-defined brominated polymers based on the bromination of hydroxyl-containing polymers. Bromination conditions for poly(2-hydroxylethyl methacrylate) (PHEMA) with diethylaminodifluorosulfinium tetrafluoroborate (XtalFluor-E), including solvents, bromine sources, additives, feeding ratios and reaction times were studied in detail. It was found that all -OH groups of PHEMA were quantitatively transformed to -Br groups and that the product maintained a narrow molecular weight distribution with a combination of XtalFluor-E, tetrabutylammonium bromide (TBAB) and 1,8-diazabicyclo(5.4.0) undec-7-ene(DBU) in dichloromethane for 24 h, at a feed ratio of [OH] : [XtalFluor-E] : [TBAB] : [DBU] = 1 : 5 : 5 : 5. Thus, well-defined poly(2-bromoethyl methacrylate) (PBEMA) and its copolymer poly(BEMA-co-MMA) were readily prepared via post-modification of the corresponding PHEMA and poly(HEMA-co-MMA) copolymer at room temperature followed by a simple precipitation procedure. This methodology was additionally applied to obtain alpha,omega-dibromo and mono-bromo terminated poly(ethylene glycol)s (PEGs) from the corresponding hydroxyl-capped PEGs. The facile and efficient bromination of hydroxyl-containing polymers has the potential to be a universal methodology for the synthesis of a diverse range of brominated polymers.