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Effects of Poly( N ‐isopropylacrylamide) (PNIPAAm) on the Conformational Change of Poly( N 5 ‐hydroxyalkyl glutamine) (PHAG) in PHAG‐PNIPAAm Block Copolymer with Temperature
Author(s) -
Cheon J. B.,
Kim B. C.,
Park Y. H.,
Park J. S.,
Moon J. Y.,
Nahm J. H.,
Cho C. S.
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010201)202:3<395::aid-macp395>3.0.co;2-s
Subject(s) - copolymer , poly(n isopropylacrylamide) , polymer chemistry , aminolysis , chemistry , circular dichroism , conformational change , aqueous solution , materials science , polymer , crystallography , stereochemistry , organic chemistry , catalysis
Diblock copolymers consisting of poly( N 5 ‐hydroxyalkylglutamine) (PHAG) and poly( N ‐isopropylacrylamide) (PNIPAAm) were prepared by aminolysis with aminoalkanols of the side‐chain ester of poly(γ‐benzyl L ‐glutamate) (PBLG) as a part of PBLG‐PNIPAAm block copolymers. The molecular weight ratio of the initial PBLG to the resulting PHAG was nearly 0.35. The effect of PNIPAAm on the conformational change of PHAG in PHAG‐PNIPAAm block copolymers with temperature was investigated by circular dichroism. Poly[ N 5 ‐(2‐hydroxyethyl)‐ L ‐glutamine] (PHEG) and the PHEG‐PNIPAAm copolymer (GNE) stayed in a randomly coiled conformation whereas poly[ N 5 ‐(3‐hydroxypropyl)‐ L ‐glutamine] (PHPG), poly( N 5 ‐(4‐hydroxybutyl)‐ L ‐glutamine) (PHBG), PHPG‐PNIPAAm copolymer (GNP), and PHBG‐PNIPAAm copolymer (GNB) underwent conformational transitions with temperature. The conformational change of the PHPG block in GNP copolymer occurred from an α‐helix to a random coil after the incorporation of PNIPAAm into the copolymer. The thermodynamic parameters of the thermally induced helix‐coil transition for PHBG and PHBG‐PNIPAAm in aqueous solution were calculated.