Preparation of 2,4-dichlorophenoxyacetic acid loaded on cysteamine-modified polydopamine and its release behaviors

摘要

With dopamine as the monomer, the model pesticide 2,4-dichlorophenoxyacetic acid (2,4D) was loaded on cysteamine (NHSH)-modified polydopamine (PDA) nanospheres [2,4-dichlorophenoxyacetic acid bound to cysteamine-modified polydopamine (2,4D-PDA-NHSH)] via the construction of amide bonds. We investigated the materials' structure, adhesive capability, and release behaviors, especially the mechanism of the release processes. The results demonstrate that the materials were spherical in appearance and adhesive. 2,4D loaded on the PDA vehicle was amorphous in structure. The amide bond between PDA and 2,4D generated by NHSH not only enhanced the loading amount of PDA from 296.28 to 692.56 mg/g but also decreased the thermal stability from 291 to 230 degrees C. The 2,4D-PDA-NHSH showed no pH responsiveness, whereas the PDA system without NHSH modification exhibited pH sensitivity. A mechanism for the observed behaviors was suggested. First-order, logistic, Weibull, and Korsmeyer-Peppas models were applied to describe the release behaviors at different pH values. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47469.