Well-Defined and Precision-Grafted Bottlebrush Polypentenamers from Variable Temperature ROMP and ATRP.

Polypentenamer macroinitiators are synthesized through variable temperature ring opening metathesis polymerization of 3-cyclopentenyl α-bromoisobutyrate, which has sufficient ring strain (Δ H p = -22.6 kJ mol -1 ) to produce targeted molar mass (<5% from theoretical), low dispersity (1.17 ≤ Đ ≤ 1.23), and high conversion (∼72%). An initiation site for atom-transfer radical polymerization at every fifth backbone carbon allows "grafting-from" of styrene with quantitative initiation and linear molar mass increase with time. These bottlebrushes retain a low dispersity ( Đ ≤ 1.34) at varying graft degrees of polymerization (5 ≤ N sc ≤ 49) and have a glass transition temperature highly sensitized to graft length. Extension of the grafts with methyl methacrylate produces a core-shell brush polymer with high molar mass (>1000 kg mol -1 ) and Đ = 1.33. This system exhibits high synthetic versatility and control with a unique flexible backbone to expand the suite of densely grafted polymers.