A series of thermoresponsive diblock copolymers of poly[2-(dimethylamino)ethyl methacrylate-block-di(ethyleneglycol) methyl ether methacrylate], poly(DMAEMA-b-DEGMA), were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerizations. The series consist of diblock and quasi diblock copolymers. Sequential monomer addition was used for the quasi diblock copolymer synthesis and the macro-chain transfer approach was utilized for the block copolymer synthesis. The focus of this contribution is the controlled variation of the ratios of DMAEMA to DEGMA in the copolymer composition, resulting in a systematic polymer library. One of the investigated block copolymer systems showed double lower critical solution temperature (LCST) behavior in water and was further investigated. The phase transitions of this block copolymer were studied in aqueous solutions by turbidimetry, dynamic light scattering (DLS), variable temperature proton nuclear magnetic resonance (1H NMR) spectroscopy, zeta poten...