An efficient route to macromonomers via ATRP and click chemistry

The combination of atom transfer radical polymerization ( ATRP) and click chemistry was employed to prepare well-defined omega-( meth) acryloyl macromonomers in an efficient manner. Poly(n-butyl acrylate) (PBA), polystyrene ( PS), and PS-b-PBA were prepared by ATRP and subsequently derivatized to contain azido end groups. The reaction of the azido-terminated polymers with alkyne-containing acrylate and methacrylate monomers resulted in near-quantitative chain end functionalization. Macromonomers of various molecular weights [ PBA: M-n = 2.2-6.4 x 10(3) g/mol (DPn) 16-49); PS: M-n = 3.2-5.9 x 10(3) g/mol (DPn) 29- 55)] and architectures were prepared by this method. The end group transformations required to incorporate the polymerizable functionality were accomplished either as a stepwise series of discrete reactions or as an in situ process, wherein azidation was immediately followed by azide-alkyne coupling in situ. In both cases, the degree of end group functionalization generally exceeded 90%. To demonstrate polymerizability, examples of omega-methacryloyloxy-PBA and omega-acryloyloxy-PS macromonomers were homopolymerized by conventional radical polymerization in toluene. The macromonomers and polymacromonomers were characterized by a combination of gel permeation chromatography using refractive index, light scattering, and viscosity detection, as well as H-1 NMR spectroscopy and H-1-H-1 NMR correlation spectroscopy (COSY). This versatile method of incorporating polymerizable end groups from commercially available reagents should be applicable to a variety of (co) polymers accessible by ATRP.