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.