Thermo-responsive block copolymers poly(ethylene glycol)-block-poly(N-acryloyl-2,2-dimethyl-1,3-oxazolidine), PEG-b-PADMO,based on linear PEG were prepared via a versatile reversible addition-fragmentation chain transfer(RAFT) polymerization.PEG_(22)(M_w = 1000) was used as the hydrophilic component,whose dehydration was the main driving force for the phase transition of these copolymers,as demonstrated by the ~1H-NMR spectra.Their lower critical solution temperatures(LCSTs) could be tuned in the range of 20℃to 35℃,by adjusting the degree of polymerization(DP) of PADMO between 14-27.Furthermore,a sharp phase transition at ca.33℃,close to the physiological temperature with minimal hysteresis,was observed for the PEG_(22)-b-PADMO_(14) copolymer.Moreover,excellent reversibility and reproducibility were displayed for the same copolymer over 10 cycles of repeated temperature change between 25℃(below the LCST) and 40℃(above the LCST). Thermo-responsive block copolymers poly (ethylene glycol) -block-poly (N-acryloyl-2,2-dimethyl-1,3-oxazolidine), PEG- fragmentation chain transfer (RAFT) polymerization.PEG_ (22) (M_w = 1000) was used as the hydrophilic component, whose dehydration was the main driving force for the phase transition of these copolymers, as demonstrated by the ~ 1H-NMR spectra.Their lower critical solution temperatures (LCSTs) could be tuned in the range of 20 ° C to 35 ° C, by adjusting the degree of polymerization (DP) of PADMO between 14-27.Furthermore, a sharp phase transition at ca.33 ° C, close to the physiological temperature with minimal hysteresis, was observed for PEG_ (22) -b-PADMO (14) copolymer. Moreover, excellent reversibility and reproducibility were displayed for the same copolymer over 10 cycles of repeated temperature change between 25 ° C below the LCST ) and 40 ° C (above the LCST).