ATRP from a Norbornenyl-Functionalized Initiator:  Balancing of Complementary Reactivity for the Preparation of α-Norbornenyl Macromonomers/ω-Haloalkyl Macroinitiators

Atom transfer radical polymerization (ATRP) using a norbornenyl-functionalized initiator was established as a new synthetic method for the preparation of macromolecules that are both α-norbornenyl macromonomers and ω-haloalkyl macroinitiators. When styrene, methyl methacrylate, and tert -butyl methacrylate were used as monomer or constituted comonomer pairs, the (co)polymerization was well-controlled and the norbornenyl functionality was intact. The resulting homopolymer or statistical copolymer-based macromonomers had linear structures, quantitative α-norbornenyl functionality, controlled number-average molecular weights ( M n = 3600−24300 Da), and narrow monomodal molecular weight distributions ( M w / M n = 1.07−1.35). Their ω-halide terminals further allowed them to serve as macroinitiators for the syntheses of block copolymer-based α-norbornenyl macromonomers by ATRP. In contrast, the norbornenyl functionality exhibited considerable competitive reactivity in the polymerizations of methyl acrylate and tert -butyl acrylate, resulting in mixed linear and branched macromonomers/macroinitiators. TGA analysis of α-norbornenyl macromonomers showed that the presence of norbornenyl functionality appreciably enhanced their thermal stability.