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pH‐Responsive Shrinkage/Swelling of a Supramolecular Hydrogel Composed of Two Small Amphiphilic Molecules
Author(s) -
Zhou ShanLai,
Matsumoto Shinji,
Tian HuaiDong,
Yamane Hiroki,
Ojida Akio,
Kiyonaka Shigeki,
Hamachi Itaru
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400677
Subject(s) - supramolecular chemistry , amphiphile , fourier transform infrared spectroscopy , carboxylate , self healing hydrogels , polymer chemistry , chemistry , swelling , chemical engineering , scanning electron microscope , copolymer , transmission electron microscopy , carboxylic acid , molecule , materials science , organic chemistry , nanotechnology , polymer , composite material , engineering
A pH‐responsive volume‐change function was successfully introduced into a supramolecular hydrogel that contained GalNAc‐appended (GalNAc= N ‐acetylgalactosamine) glutamate ester 1 by the simple mixing of it with an appropriate amount of 2 a or 2 b amphiphilic carboxylic acid. In the 1:1 mixture ( 1 : 2 ), the hydrogel swelled under neutral pH conditions, but shrank to almost half of its original volume under acidic pH conditions. The structure and pH response of the mixed hydrogel were characterized by using X‐ray diffraction (XRD), confocal laser scanning microscopy (CLSM), transmission or scanning electron microscopy (TEM, SEM), and Fourier transform IR (FTIR) spectroscopy. Well‐developed fibers formed a stable hydrogel by self‐assembly, and under acidic conditions the charge of the carboxylic acid terminal (from the carboxylate anion) was neutralized and then these fibers became densely packed. This macroscopic pH response was also applied to the pH‐triggered release of bioactive substances. In this mixed supramolecular hydrogel, the hydrogelator 1 provides a stable hydrogel structure and the additive 2 acts as a commander that is sensitive to an environmental pH signal. The present supramolecular copolymerization strategy should be useful for the construction of novel, stimuli‐responsive, soft materials.