An immortal N‐(diphenylphosphanyl)‐1,3‐diisopropyl‐4,5‐dimethyl‐1,3‐dihydro‐2H‐imidazol‐2‐imine/diisobutyl (2,6‐di‐tert‐butyl‐4‐methylphenoxy) aluminum (P(NIiPr)Ph2/(BHT)AliBu2)‐based frustrated Lewis pair (FLP) polymerization strategy is presented for rapid and scalable synthesis of the sequence‐controlled multiblock copolymers at room temperature. Without addition of extra initiator or catalyst and complex synthetic procedure, this method enabled a tripentacontablock copolymer (n=53, k=4, dpn=50) to be achieved with the highest reported block number (n=53) and molecular weight (Mn=310 kg mol−1) within 30 min. More importantly, this FLP polymerization strategy provided access to the multiblock copolymers with tailored properties by precisely adjusting the monomer sequence and block numbers.