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To improve the utilization rate of pesticides and reduce the economic losses and environmental hazards caused by pesticide loss, the self-assembly layer of poly (octadecylsiloxane) (PODS) was prepared by hydrolysis, self-assembly and polycondensation of octadecyltrichlorosilane (OTS) on the surface of rapeseed meal (RSM) with octadecyltrichlorosilane (OTS) and p-aminoazobenzene (AAB) as modifiers. At the same time, AAB with photoisomerism was attached to RSM surface to synthesize RSM-PODS/AAB pesticide carrier with photoresponsiveness. Its structure and composition were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), UV-Vis spectroscopy and contact angle measurement device. The results showed that the loading rate of modified RSM was 21.4% higher than that of original RSM, and the cumulative release rate of pinoxaden was 83% in 72 h in the dark. The cumulative release rate of RSM-PODS/AAB was 95% after UV-Vis irradiation for 4 h and 92% after sunlight irradiation for 6 h. The application results showed that RSM-PODS/AAB loaded with pesticides had good UV-Vis and sunlight controlled release performance. The light responsive lipophilic pesticide carrier could effectively control the drug release behavior through UV-Vis and sunlight response. [ABSTRACT FROM AUTHOR]

Droplets evaporation on plant leaves plays an important role in the utilization of pesticides. Although traditional surfactants can change the evaporation mode or evaporation rate of droplets, they cannot adjust the evaporation process effectively according to external stimuli. In this research, a photo-responsive diacetylene-based cationic surfactant (PCDA-C6-NH3+) was designed and synthesized, where 10,12-pentacosadiynoic acid and protonated terminal amine were used as the photo-responsive motiey and the hydrophilic cation, respectively. The UV light-induced topochemical polymerization of PCDA-C6-NH3+ was studied by UV-Vis spectroscopy. Its surface activity and evaporation behavior before and after UV irradiation were analyzed by static surface tension and dynamic contact angle. The results showed that the aggregation state of PCDA-C6-NH3+ can be regulated by UV light during the droplets evaporation process, because of its topochemical polymerization. This work has provided a new strategy to adjust the evaporation of droplets, which is of great significance for improving the utilization rate of pesticides. [ABSTRACT FROM AUTHOR]