期刊
JOURNAL OF COLLOID AND INTERFACE SCIENCE
卷 582, 期 -, 页码 1075-1084出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2020.08.081
关键词
Microgels; Spiropyran; N-vinylcaprolactam; Temperature responsiveness; Photoswitching; Visible light responsiveness
资金
- DFG [SFB 985]
- China Scholarship Council (CSC)
A novel method was developed to synthesize light and temperature dual-responsive spiropyran-modified poly(N-vinylcaprolactam) microgels with high spiropyran content. The reversible light and temperature responsiveness of the microgels was demonstrated through experiments, showing potential applications in biotechnology and medicine.
Hypothesis: Light-responsive microgels are interesting colloidal systems with potential applications in the biotechnology and medicine. However, synthesis of light-responsive microgels with high loading of photoswitchable molecules is still very challenging. Experiments: Herein we developed a new method to synthesize light and temperature dual-responsive spiropyran-modified poly(N-vinylcaprolactam) microgels. The novel and straightforward microgels syn-thesis route involved: a) synthesis of poly(N-vinylcaprolactam-co-vinylformamide) copolymers via RAFT polymerization followed by the hydrolysis to obtain primary amine groups, b) attachment of carboxyl modified spiropyran molecules to polymer chains via coupling, and c) crosslinking of spiropyranmodified polymer chains in W/O miniemulsion to form microgels. Findings: Via this method, we successfully synthesized poly(N-vinylcaprolactam) microgels containing more than 10 mol% spiropyran. The reversible light responsiveness of the spiropyran-modified copolymers and microgels in aqueous solution, which originates from the spiropyran photoisomerization under irradiation with different wavelengths, was demonstrated by UV-Vis spectroscopy. Spiropyran-modified copolymers demonstrate shift of the lower critical solution temperature (LCST) due to the polarity change of spiropyran molecules under dark, UV and visible light. Surprisingly, dynamic light scattering (DLS) results show that the microgels based on the same copolymers are less affected by UV irradiation. Microgels are swollen in darkness when spiropyran molecules are in the polar, merocyanine form, and collapse after irradiation with visible light, due to the transformation of spiropyran to the relatively nonpolar, closed spirocyclic form. In addition, the spiropyran-modified microgels exhibit reversible tem-perature responsiveness by presenting a volume phase transition in water from a swollen state to a collapsed state with increasing temperature and the transition temperature decreased compared to the pristine microgels due to the hydrophobicity of spiropyran units. (c) 2020 Elsevier Inc. All rights reserved.
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