Cp2TiCl-catalyzed epoxide radical ring opening:: A new initiating methodology for graft copolymer synthesis

The first example of the use of epoxides in radical grafting copolymerizations was exemplified by the grafting of poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), poly(butyl acrylate) (PBA), and poly(styrene) (PSt) from poly(glycidyl methacrylate) (PGMA) and from copolymers of GMA with MMA and St as well as by the iterative synthesis of mixed arm graft copolymers such as (PGMA-g-PMMA)-g-PSt and ((PGMA-g-PMMA)-g-PSt)-g-PBMA with a wide range of molecular weights and compositions. The grafting was demonstrated by a combination of gel permeation chromatography (GPC), NMR, and differential scanning calorimetry (DSC) investigations. The polymerization is initiated by the Cp2TiCl-catalyzed radical ring opening of the epoxide group of GMA and is optionally controlled by CuBr2/bipyridyl. This methodology does not require any epoxide protection/deprotection steps and provides the typical advantages of radical polymerizations and convenient access to complex macromolecular architectures.