An Efficient Route to Macromonomers via ATRP and Click Chemistry

Abstract

The combination of atom transfer radical polymerization (ATRP) and click chemistry was employed to prepare well-defined ω-(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: Mn = 2.2−6.4 × 103 g/mol (DPn = 16−49); PS: Mn = 3.2−5.9 × 103 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 ω-methacryloyloxy−PBA and ω-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 1H NMR spectroscopy and 1H−1H 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.