PAPER CANCELLED: Characterization of Brominated Natural Rubber By Solution State 2D NMR Spectroscopy

Bromination is one of the important reactions to modify natural rubber, since bromine groups of brominated natural rubber is useful for living radical polymerization and Suzuki-Miyaura cross-coupling reactions. For instance, grafted natural rubber and phenyl modified natural rubber were prepared from brominated natural rubber, in the last decade; so that, mechanical properties of natural rubber were dramatically improved by living radical polymerization and Suzuki-Miyaura cross-coupling reaction. Based on the previous results, we may prepare high performance natural rubber when we precisely control the structure of brominated natural rubber as a source.

In the present work, an attempt to characterize brominated natural rubber was carried out. Natural rubber, deproteinized with urea and surfactant, was brominated using N-bromosuccinimide (NBS) in a dichloromethane solution of the rubber. The amount of NBS controlled the bromine content. The resulting brominated natural rubber was characterized by 1D and 2D-NMR spectroscopy. Small signals were assigned to CH₂ and CH₃ groups linking to bromine atom. Cis-trans isomerization of isoprene units was found to take place during bromination of natural rubber with NBS.