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Water‐Soluble Thermoresponsive α ‐Helical Polypeptide with an Upper Critical Solution Temperature: Synthesis, Characterization, and Thermoresponsive Phase Transition Behaviors
Author(s) -
Deng Yong,
Xu Yanzhi,
Wang Xi,
Yuan Qiulin,
Ling Ying,
Tang Haoyu
Publication year - 2015
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201400625
Subject(s) - upper critical solution temperature , lower critical solution temperature , polymerization , circular dichroism , phase transition , chemistry , polymer chemistry , ring opening polymerization , miscibility , helix (gastropod) , thermoresponsive polymers in chromatography , phase (matter) , materials science , crystallography , polymer , thermodynamics , organic chemistry , copolymer , ecology , physics , biology , snail , reversed phase chromatography
Water‐soluble polypeptides bearing 1‐alkylimidazolium (methyl or n‐butyl) and various counter‐anions (i.e., Cl − , I − or BF 4 − ) are prepared by ring‐opening polymerization of γ ‐4‐chloromethylbenzyl‐ l ‐glutamate‐based N ‐carboxyanhydride ( 3 ), post‐polymerization of poly( γ ‐4‐chloromethylbenzyl‐ l ‐glutamate) ( 4 ), and ion‐exchange reaction. Circular dichroism (CD) analysis reveals that the resulting polypeptides adopt an α ‐helical conformation in water with a fractional helicity in the range of 30%–56% at 20 °C and exhibit good conformational stability against temperature variations. The polypeptides exhibit lower critical solution temperature (LCST)‐type or upper critical solution temperature (UCST)‐type transitions in organic solvents or in water. The UCST‐type transition temperature ( T pt ) in water is independent on the molecular weight, yet it decreases upon addition of NaCl and increases upon addition of NaI or NaBF 4 , suggesting a mainly electrostatic interaction mechanism.