The urgent need to mitigate climate change has spurred research into innovative carbon dioxide (CO₂) capture materials. In this study, the design and synthesis of CO₂-responsive diblock copolymers, poly (N-[3-(dimethylamino)propyl]-acrylamide)-b-poly(methyl methacrylate) (PDMAPAm-b-PMMA) are focused on via a two-step reversible addition−fragmentation chain-transfer (RAFT) polymerization as well as the application of the synthesized diblock copolymer as a membrane for CO₂ capture. The resulting diblock copolymer possesses distinct blocks with varying properties. The poly (N-[3-(dimethylamino)propyl]-acrylamide) (PDMAPAm) block provides CO2-responsive behavior, while the poly(methyl methacrylate) (PMMA) block contributes to mechanical stability. The gas transport properties of the fabricated thin-film composite membrane made of PDMAPAm-b-PMMA are measured. It is determined that the copolymer exhibits dual responsiveness towards CO₂ and can be tailored for use in fabrication of membranes for direct air capture (DAC).