Synthesis, Characterization, and thermoresponsive properties of Helical Polypeptides Derivatized from Poly(γ−4-(3-chloropropoxycarbonyl)benzyl-L-glutamate)

A series of side-chain-functionalized α-helical polypeptides, i.e., poly(γ-4-(3-chloropropoxycarbonyl)benzyl- L -glutamate) (6) have been prepared from n-butylamine initiated ring-opening polymerization (ROP) of γ-4-(3-chloropropoxycarbonyl)benzyl- L -glutamic acid-based N -carboxyanhydride. Polypeptides bearing oligo-ethylene-glycol (OEG) groups or 1-butylimidazolium salts were prepared from 6 via copper-mediated [2+3] alkyne-azide 1,3-dipolar cycloaddition or nuleophilic substitution, respectively. CD and FTIR analysis revealed that the polymers adopt α-helical conformations both in solution and the solid state. Polymers bearing OEG (m = 3) side-chains showed reversible LCST-type phase transition behaviors in water while polymers bearing 1-butylimidazolium and I − counter-anions exhibited reversible UCST-type transitions in water. Variable-temperature UV-vis analysis revealed that the phase transition temperatures ( T pt s) were dependent on the main-chain length and polymeric concentration. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53 , 2469–2480