Facile synthesis of advanced gradient polymers with sequence control using furan-protected maleimide as a comonomer

Gradient polymers are intriguing structures due to their unknown structure/property relationships and potential applications. Herein, advanced gradient copolymers were prepared from comonomers methyl methacrylate and furan-protected propyl maleimide (FPMI) via a reversible addition–fragmentation chain-transfer (RAFT) polymerization. During RAFT polymerization at 100 °C, propyl maleimide (PMI) was generated in situ from FPMI via a retro-Diels–Alder (rDA) reaction to undergo copolymerization in a gradient manner due to intrinsic reactivity ratios. At 40 °C, the rDA reaction for PMI release was not triggered. Many unprecedented gradient polymers, including simultaneous, hierarchical, di-block, symmetrical, and tri-block gradient copolymers, were successfully fabricated. Finally, the sequence-dependent thermal properties were explored. This work greatly enriches the library of gradient polymers and advances research into sequence-controlled polymerization.