Fine control of the molecular weight and polymer dispersity via a latent monomeric retarder

The demand to control the molecular weight distribution (MWD) of polymers has gained an unprecedented upsurge for its great importance in enhancing polymer properties. This motivates the development of efficient synthetic methods aiming to predicatively and precisely tailor the MWD. In this work, 2-bromomaleimide (MBr) was used as a monomeric retarder to hinder the chain growth in the reversible addition–fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA), resulting in the broadening of the MWD of PMMA with a high dispersity (Đ). Đ could be well tuned between 1.2 and 2.0 by changing the feed ratio of the initial concentration of MBr to the chain transfer agent (CTA). To further control the MW and Đ, furan-protected MBr (FMBr), referred to as a latent monomeric retarder, was used to manipulate the release of MBr via a retro-Diels–Alder reaction at an elevated temperature. As FMBr remained intact at a low temperature (40 °C) while it underwent deprotection at a high temperature (110 °C), the onset of MBr release could be well controlled by temperature programming to fine-tune the MWD. The concept of a latent monomeric retarder introduced a simple and non-invasive way to finely adjust the MW and Đ, advancing the methodology research on MWD control.