Psarrou Maria, Chatzaki Ioanna, Mavromanolakis Antonis, Manouras Theodore, Vlassopoulos Dimitris, Vamvakaki Maria
Department of Materials Science and Engineering, University of Crete, Heraklion, Crete, 700 13, Greece.
Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, Heraklion, Crete, 700 13, Greece.
Angew Chem Int Ed Engl. 2025 Sep 1;64(36):e202508160. doi: 10.1002/anie.202508160. Epub 2025 Jul 26.
Stimuli-reversible, chemically cross-linked polymers capable of altering their physicochemical and mechanical properties on demand, upon application of external stimuli (e.g., light, temperature), are highly desirable for the development of multifunctional materials. Herein, we report a facile chemical platform for the synthesis of photodegradable and thermo-reversible, model hydrogels consisting of poly(ethylene glycol) (PEG) as the elastic strands and dithioacetal moieties at the cross-link points. The gels were synthesized via an acid-catalyzed step-growth reaction of a difunctional PEG-thiol macromer with a wisely selected aromatic dialdehyde cross-linker. The formation of the photosensitive dithioacetal bonds at the cross-links rendered the hydrogels photodegradable, whereas the production of the initial comonomers as the main photoproducts after irradiation endowed the material with thermoreversible properties. The linear viscoelastic behavior of water-swollen gels, their photodegradation under UV (λ = 254 nm) irradiation at very low intensity (0.063 mW cm), and the reversible reformation of the hydrogel upon heating were investigated by dynamic shear rheology. Mechanistic insights for the photodegradation mechanism of the system were gained by H NMR spectroscopy and kinetic studies on a model dithioacetal compound.
对于多功能材料的开发而言，能够在施加外部刺激（如光、温度）时按需改变其物理化学和机械性能的刺激可逆、化学交联聚合物是非常理想的。在此，我们报道了一个简便的化学平台，用于合成由聚乙二醇（PEG）作为弹性链且在交联点处含有二硫缩醛部分的光降解和热可逆模型水凝胶。这些凝胶是通过双官能PEG-硫醇大分子单体与精心选择的芳族二醛交联剂的酸催化逐步增长反应合成的。交联处光敏二硫缩醛键的形成使水凝胶具有光降解性，而辐照后作为主要光产物的初始共聚单体的产生赋予了该材料热可逆性能。通过动态剪切流变学研究了水溶胀凝胶的线性粘弹性行为、它们在极低强度（0.063 mW/cm²）的紫外（λ = 254 nm）辐照下的光降解以及加热时水凝胶的可逆再形成。通过¹H NMR光谱和对模型二硫缩醛化合物的动力学研究获得了该系统光降解机理的机理见解。
