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Novel Redox Hydrogel by in Situ Polymerization Using Chitosan as Template and Its Applications

Author: HeJian
Tutor: ZhangYongJun
School: Nankai University
Course: Polymer Chemistry and Physics
Keywords: Template polymerization Redox-active LBL film Hydrogel
CLC: O648.17
Type: PhD thesis
Year: 2013
Downloads: 16
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Abstract


A novel redox hydrogel was synthesized using poly(hydroquinone)(PHQ) as redox couple and chitosan as matrix by simple exposing the chitosan/HQ acidic solution to the air. PHQ was synthesized by the in-situ oxidative polymerization of HQ using chitosan as template and oxygen as oxidant. This is first report of the template oxidative polymerization of HQ. Kinetic studies show that:when the chitosan/hydroquinone molar ratio of is less than0.96, the polymerization rate increases linearly with increasing chitosan concentration, and beyond this point, the reaction rate keeps constant. The results indicate that the template polymerization of hydroquinone processes following the "Pick up" mechanism. And the order of the reaction for HQ is calculated as0.375, and the activation energy is70.0kJ/mol. The in situ polymerization of hydroquinone results in the gelation of aqueous solution which is caused by hydrogen-bond between hydroquinone and chitosan. With increasing chitosan and hydroquinone concentration as well as increasing temperature, the gelation time decreases. Electrochemical experiments show that the hydrogel is redox active. The hydrogel may be found applications in the biomedical field.In order to exploit the potential applications of chitosan/PHQ hydrogel, a novel redox hydrogel film was synthesized using chitosan hydrogel as matrix and PHQ as redox couple. First, the single-component chitosan LBL film was fabricated uniformly and reproducibly by glutaraldehyde-mediated assembly of chitosan. Then, the chitosan film was treated with an acidic solution of hydroquinone to introduce PHQ. The introduced PHQ could result in the increased roughness and thickness of the film. It is proved that the oxygen is used as oxidant and chitosan is used as a template in the polymerization of HQ. Cyclic voltammetry data confirms that after the introduction of PHQ, chitosan film became redox-active. Therefore, the new redox-active film may be found the potential applications in amperometric biosensors.The oxidative polymerization of catechol could also process using chitosan as template and oxygen as the oxidant, and the in-situ polymerization generated polycatechol (PCQ), which was characterized by UV and FTIR. This is the first report of the template polymerization of CQ. Kinetic studies shows:the template polymerization of catechol follows the "Pick up" mechanism, and the order of the polymerization reaction for catechol is0.537, and the activation energy is39.35kJ/mol. The physical crosslinking between PCQ and chitosan results in the gelation of the solution. With the increasing chitosan and catechol concentration and the increasing temperature, the gelation time decreased. The CV curves of chitosan/PCQ hydrogel is also redox active. The hydrogel may be found applications in the biomedical field, and the polymerization of CQ is useful for the wastewater disposal.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Colloid chemistry ( physical and chemical dispersion system ) > Colloid > Gel and soft
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