Preparation And Properties Evaluation Of Stimulus-responsive Star Polymer As Pesticide Carrier

Pesticides are one of the important production materials in agricultural production,including pesticides,fungicides,herbicides,acaricides and so on.The bioavailability of traditional pesticide formulations is low due to dust drift,runoff rolling and other reasons.One of the ways to solve this problem is to use nanotechnology and environmental stimulus responsive pesticide carrier to realize the controllable and accurate release of pesticide active components.In this thesis,three environmentally responsive nano pesticide carriers were designed and prepared to load hydrophobic pesticides.On the one hand,the hydrophilicity of pesticides was improved.On the other hand,pesticides were released through environmental response to effectively improve the bioavailability of pesticides.The specific research contents are as follows:1.This portion is based on the relationship between the growth and reproduction of cotton aphids and temperature.That is,cotton aphids can not produce sexual aphids below 14°C and the maximum net reproduction rate at 21°C.Withβ-Cyclodextrin（β-CD）as star center,temperature responsive2-methoxyethoxymethyl methacrylate（MEO₂MA）as hydrophilic monomer and tert-butyl acrylate（t BA）as hydrophobic Monomer.Amphiphilic star polymers with different low critical transition temperatures（LCST）were constructed by atom transfer radical polymerization（ATRP）.The hydrophobic insecticide imidacloprid（IMI）was loaded by self-assembly to realize the on-demand regulated release of IMI.Select the one with LCST value of 21℃β-CD-P0 as the research objectives.The results showed that when the temperature was 14℃,21℃and 27℃,the cumulative drug release of IMI was 20%,36%and 48%respectively.The critical micelle concentration of the polymer is 8.71 mg/L and has storage stability for at least 28 days.The wettability experiment showed that the hydrophilicity of imidacloprid was stronger and easier to spread on the leaves.2.After cotton is invaded by aphids,its defense system function decreases and it is more vulnerable to bacterial infection.At the same time,the plant itself will quickly produce reactive oxygen species（ROS）when invaded by external bacteria.In this chapter,ROS responsive drug release carrier materials are designed and prepared to deal with bacterial infection.β-Cyclodextrin（β-CD）andε-Caprolactone（ε-CL）hydrophobic host after ring opening polymerization（β-CD-PCL）.After modification with adamantane and polyethylene glycol monomethyl ether(m PEG₅₀₀₀-OH),hydrophilic guest(m PEG₅₀₀₀-TK-Ad)was formed.They interact with each other to form amphiphilic polymer(m PEG₅₀₀₀-TK-Ad@β-CD-PCL),loaded with bactericide carbendazim by self-assembly.The in vitro sustained-release experiment showed that the polymer had ROS response characteristics.The 120 h sustained-release test without ROS showed that the cumulative release of carbendazim was 30%.The release rate of pesticide carbendazim could be increased to 57%under the stimulation of ROS.The antibacterial experiment showed that when the effective concentration of carbendazim was 30 mg/L,the inhibition rate of colony was 92.23%.The critical micelle concentration of the polymer is 8.30 mg/L and has storage stability for at least 14 days and good wettability.3.Based on the design idea of amphiphilic polymer carrier in the previous chapter,this chapter is to simplify the synthesis methods and steps of polymer carrier and improve its feasibility in agricultural production.With pentaerythritol（PER）as the star initiator center,andε-Caprolactone（ε-CL）after ring opening polymerization,the modified polyethylene glycol monomethyl ether(TK-m PEG₅₀₀₀)was grafted to form amphiphilic star polymer PER-PCL-TK-m PEG₅₀₀₀.The bactericide carbendazim was loaded in the form of self-assembly.The in vitro sustained-release experiment showed that the polymer had ROS response characteristics.The 120 h sustained-release test without ROS showed that the cumulative release of carbendazim was 40%.The release rate of pesticide carbendazim could be increased to 61%under the stimulation of ROS.The antibacterial experiment showed that when the effective concentration of carbendazim was 30 mg/L,the inhibition rate of colony was 91.60%.The critical micelle concentration of the polymer is only 4.37 mg/L,and has storage stability for at least 14 days and good wettability.