将5,10,15,20-四(4-羧基甲氧基苯基)卟啉修饰的壳聚糖与丙烯酰胺共聚制备了水凝胶并对其结构和性能进行表征。结果表明:卟啉修饰壳聚糖的加入使水凝胶具有酸碱响应的光谱性质和力学性能。在碱性条件下卟啉分子间具有静电排斥力,不易聚集,而酸性条件下则相反。同时,碱性环境下水凝胶中的壳聚糖能够形成结晶微区,使其力学性质明显增强。此外,水凝胶具有形状记忆功能,并且在形状变化过程中伴随着光谱的可逆变化。
The realization of multiple changes of hydrogels under single stimulation is an important issue to investigate the internal structure of hydrogels,and to broaden the applications of hydrogels.Porphyrin derivatives are compounds that exist widely in nature,and have strong ultraviolet absorption and fluorescence spectrum.Porphyrin monomers can sensitize molecular oxygen to form singlet oxygen,and are widely used in catalysis,photodynamic physiotherapy,and bacteriostasis.After the porphyrin molecules form aggregates,not only their spectral properties change,but their ability to sensitize oxygen decreases.Therefore,regulating the aggregation state of porphyrin molecules can effectively regulate their properties.5,10,15,20-tetra (4-carboxymethoxyphenyl) porphyrin (H2TCMPP) modified chitosan was prepared by condensation reaction,and its molecular structure was characterized by infrared spectrum and ultraviolet absorption spectrum.Hydrogels based on modified chitosan and acrylamide were prepared by one pot method.The hydrogel shown an acid-base response ultraviolet absorption spectrum and a fluorescence spectrum,and the change of the spectrum can be carried out reversibly.This was because H2TCMPP formed intermolecular aggregates in acidic solution.However,the porphyrin had electrostatic repulsion between molecules in alkaline solution due to the formation of carboxylate,which made the aggregation not easy to occur.In addition,the mechanical properties of the hydrogel after NaOH treatment can be significantly enhanced since the molecular chain of chitosan in the alkaline solution can form crystalline microdomains through hydrogen bonding interactions.Meanwhile,this also imparted the shape memory properties of the hydrogel.The temporary shape of the gel can be fixed by the crystalline micro-curves formed in NaOH.And it can retain its permanent shape in HCl.Therefore,under the single NaOH treatment,the hydrogel can realize the changes of optical and mechanical properties simultaneously.Furthermore,the change of porphyrin molecules during this process may endow the hydrogel with controllable photosensitization ability.
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