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.