Thermoresponsive polypeptides bearing oligo(ethylene glycol) (OEG) pendants (i.e., P1-OEG(x) and P2-OEG(x), x=3, 7) were synthesized by copper-mediated 1,3-dipolar cycloaddition with high grafting efficiency (97%) between side-chain clickable polypeptides, namely poly(-4-(propargoxycarbonyl)benzyl-l-glutamate) (P1) or poly(-4-(4-propargoxyphenoxycarbonyl)benzyl-l-glutamate) (P2) and azido functionalized OEG (N-3-OEG(x)). P1 and P2 with similar degree of polymerization (DP=35 or 37) were prepared from triethylamine initiated ring-opening polymerization of respective N-carboxyanhydrides. P1-OEG(x) (x=3, 7) and P2-OEG(7) showed reversible UCST-type phase transitions in various alcoholic solvents (e.g., ethanol, propanol, n-butanol, and n-pentanol). P2-OEG(3) also showed reversible UCST-type phase transitions in ethanol/water solvent mixtures at the weight percentage of ethanol no less than 50 wt %. P1-OEG(7) and P2-OEG(7) showed reversible LCST-type phase transitions in aqueous solutions. Variable-temperature UV-vis spectroscopy revealed that the LCST-type phase transition temperature (T-pt) of P2-OEG(7) with benzoic acid phenyl ester linkages was at around body temperature and it was barely changed with the variation of polymer concentration, yet it showed noticeable dependence on the nature of salt (i.e., NaCl, NaBr, NaI, or KCl) and salt concentration in the range of 0-300 mM. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 163-173