Preparation And Properties Of Functional Polymers For Controlled Release Of Avermectin

Avermectin (Av) is susceptible to oxidation and photolysis, resulting in unstability under UV irradiation and short half-life. Although some pesticides can avoid degradation and provide sustained release, few research studies that how to prolong the retention period of Av in crop foliar, delay the photodegradation, release rate according to the external environment change and prepare environmental friendly formulations. Dopamine chemistry, inspired by the adhesive properties of mussel proteins, could deposit a polydopamine (PDA) layer on different substrates in weak alkaline solution and povide a versatile coatings to graft polymer brushes. Such chemistry features could be used for feasibly designing PDA-based materials with stimuli-responsive preperties, which have rarely been investigated and afford an alternative structure for specific applications. Moreover, combining the characteristics of biodegradable and snvironmentally friendly hydrogel, prepared a temperature and pH stimuli-responsive avermectin release system. In this paper, these works have been done aim to the problems mentioned above.1. Study on UV-shielding and controlled-release properties of polydopamine coating for avermectin. The mussel-inspired polydopamine coated avermectin composites are prepared through the oxidization self-polymerization of dopamine and the multistep depositon method. Importantly, there still is a large amount of undecomposed avermectin in the polydopamine layer after UV irradiation. Moreover, the thicker the polydopamine coating of the composites, the longer the release and the better the UV-shielding performance.2. Adhesive Polydopamine Coated Avermectin Microcapsules for Prolonging Foliar Pesticide Retention. This work developed a novel method for enabling the controlled release of Av by emulsion interfacial polymerization. The proposed microcapsules showed remarkable loading ability for Av. Av@PDA could effectively protect Av against photo-degradation and imparted Av@PDA microcapsules with excellent sustained-release properties. Higher pH values and temperatures intensified Av release. Av showed good adhesion properties and long residence times on cotton and corn leaves. Meanwhile, these microcapsules had good mechanical stability property. Hence, Av@PDA microcapsules may be developed as a resource-saving and environment-friendly pesticide formulation.3. Mussel-Inspired thermosensitive microcapsules for controlled pesticide release via metal-free surface-initiated photopolymerization. First, we describe a simple yet extremely versatile and generalized surface polymer modification approach based on a surface initiated polymerization from a polydopamine (PDA) layer. Second, SiO2 spheres are used as templates to prepare PDA microparticles, and the thermal responsive PDMAEMA thin films are grafted on PDA surfaces through a metal-free surface-initiated photopolymerization approach without adding any photoinitiator or photosensitizer under UV light, the subsequent acid etching yields PDMAEMA-g-PDA hollow microcapsules. The PDMAEMA coated PDA microcapsules exhibit temperature controlled-release performance.4. A facile route to fabricate a biodegradable hydrogel for controlled pesticide release. We have demonstrated a convenient and rapid synthetic approach for the preparation of Av-HGs based on a hydrazone bond induced hydrogel. Av-HG displays the desired temperature and pH controlled-release properties of avermectin and has a remarkable loading ability for avermectin. Moreover, this system provides a potential method to control pesticide release and reduce the pollution risk to the environment.