pH-responsive shrinkage/swelling of a supramolecular hydrogel composed of two small amphiphilic molecules

Shan Lai Zhou, Shinji Matsumoto, Huai Dong Tian, Hiroki Yamane, Akio Ojida, Shigeki Kiyonaka, Itaru Hamachi

Research output: Contribution to journalArticlepeer-review

150 Citations (Scopus)


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 2b 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.

Original languageEnglish
Pages (from-to)1130-1136
Number of pages7
JournalChemistry - A European Journal
Issue number4
Publication statusPublished - Feb 4 2005

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry


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