Ceiling Degree of Polymerization for Brush Polymers Prepared via ROMP of Poly(tert-Butyl Acrylate) Macromonomers

Controlled preparation of brush polymers is important in the design of functional materials. In this study, poly( tert -butyl acrylate) macromonomers functionalized with norbornenyl end group(NB-P t BA) were synthesized via atom transfer radical polymerization in three different molecular weights, 2000(NB-P t BA-2k), 3000(NB-P t BA-3k), and 8000(NB-P t BA-8k). Additionally, brush polymers with P t BA as side chains were synthesized via ring-opening metathesis polymerization(ROMP). Kinetic studies on ROMP of NB-P t BA showed that there was a ceiling degree of polymerization(CDP) for the brush polymers, beyond which the polymerization of NB-P t BA was out of control. For brush polymers of P[NB-P t BA-2k] and P[NB-P t BA-3k], CDPs were estimated to be ca . 400, but the value of P[NB-P t BA-8k] was ca . 100. Therefore, the controlled ROMP of brush polymers was critical at the CDP limit with increased macromonomer molecular weight.