Light-induced spatial control of pH-jump reaction at smart gel interface

Prapatsorn Techawanitchai, Mitsuhiro Ebara, Naokazu Idota, Takao Aoyagi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


We proposed here a 'smart' control of an interface movement of proton diffusion in temperature- and pH-responsive hydrogels using a light-induced spatial pH-jump reaction. A photoinitiated proton-releasing reaction of o-nitrobenzaldehyde (NBA) was integrated into poly(N-isopropylacrylamide-o-2-carboxyisopropylacrylamide) (P(NIPAAm-co-CIPAAm)) hydrogels. NBA-integrated hydrogels demonstrated quick release of proton upon UV irradiation, allowing the pH inside the gel to decrease below the pK a of P(NIPAAm-co-CIPAAm) within a minute. The NBA-integrated gel was shown to shrink rapidly upon UV irradiation without polymer " skin layer" formation due to a uniform decrease of pH inside the gel. Spatial control of gel shrinking was also created by irradiating UV light to a limited region of the gel through a photomask. The interface of proton diffusion (" active interface" ) gradually moved toward non-illuminated area. The apparent position of " active interface" however, did not change remarkably above the LCST, while protons continuously diffused outward direction. This is because the " active interface" also moved inward direction as gel shrank above the LCST. As a result, slow movement of the apparent interface was observed. The NBA-integrated gel was also successfully employed for the controlled release of an entrapped dextran in a light controlled manner. This system is highly promising as smart platforms for triggered and programmed transportation of drugs.

Original languageEnglish
Pages (from-to)53-59
Number of pages7
JournalColloids and Surfaces B: Biointerfaces
Publication statusPublished - 2012 Nov 1
Externally publishedYes


  • PH-jump reaction
  • PH-responsive hydrogels
  • Photo-acid generator (PAG)
  • Proton diffusion
  • Smart interface

ASJC Scopus subject areas

  • Biotechnology
  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces


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