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We synthesized oligomer mixtures of (2,4-dichlorophenoxy) acetyl-(R,S)-3-hydroxybutyric acid and (3,6-dichloro-2-methoxy) benzoyl-(R,S)-3-hydroxybutyric acid, transforming (2,4-dichlorophenoxy)acetic acid (2,4-D) and (3,6-dichloro-2-methoxy)benzoic acid (dicamba) into low volatile oligomers with greater lipophilicity than the parent acids. Synthesis of the functional oligomers was carried out via the ring-opening polymerization of (R,S)-β-butyrolactone initiated by (2,4-dichlorophenoxy) acetate or (3,6-dichloro-2-methoxy) benzoate potassium salts in the presence of bulky complexing agents. The 3-hydroxybutyric acid (3-HBA) oligomers were susceptible to (bio)degradation via ester bond hydrolysis, which enables controlled release of the active ingredient. For each 3-HBA oligomer mixture, we determined the molecular structure and molecular weight by means of size exclusion chromatography, proton magnetic resonance spectrometry, and electro-spray ionization mass spectrometry. In addition, we evaluated the herbicidal efficacy of the 3-HBA oligomers on several broad-leaved species and crop injury to winter wheat relative to conventionally formulated dimethyl ammonium (DMA) salts. The death of weeds treated with the 2,4-D and dicamba 3-HBA oligomers was delayed relative to that induced by the DMA salts. This delayed activity may be explained by the controlled release of the 3-HBA oligomers.
2,4-D, dicamba, controlled release, delayed uptake, biodegradable oligomers, weed control
Kowalski, Witold J.
Professor, Jan Dlugosz Univ., Institute of Chemistry, Environmental Protection and Biotechnology, Czestochowa,
Associate Professor, Institute of Plant Protection, National Research Institute, Sosnicowice Branch, Sosnicowice,
Senior Researcher, Institute of Plant Protection, National Research Institute, Sosnicowice Branch, Sosnicowice,
Kowalczuk, Marek M.
Professor, Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze,
Ph.D. Student, Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze,
Institute of Chemistry, Environmental Protection and Biotechnology, Czestochowa,