Bis(2,4‐dinitrophenyl ether)s of the water‐soluble polymer poly(ethylene glycol) (PEG) are low‐loading models for time‐release herbicide systems and may potentially hydrolyse in basic aqueous media according to a mechanistic menu that includes elimination, aliphatic and/or aromatic displacement, as well as anchimerically assisted displacement involving O‐6 of the plyether backbone. This paper study reports kinetic (second‐order rate constnts, k2, and activation parameters) and 1H (400 MHz) NMR results (monitoring of the reaction in DMSO‐d6 and D2O) for the alkaline hydrolysis of a series of these ethers (DNPEGs). DNPEGs with varying average molecular weights (MW) of the polymer backbone (DNPEG‐59, ‐1900 and ‐3200, where the numbers refer to the PEG MW) were studied, as were DNPEGs that differed only in the degree of end‐group substitution, namely DNPEG‐1900‐59 and ‐81 (where the final numbers refer to the percentage substitution). The 1H NMR studies show significant aryl ring hydrogen–deuterium exchange in the hydroxide–DMSO‐d6 and hydroxide–D2O systems examined, as well as a poly(ethylene glycol) alkoxide (PEG‐O−) C‐1 adduct in DMSO‐d6; the PEG‐O− is displaced in an SNAr fashion from DNPEG as a result of initial hydroxide attack at C‐1 of DNPEG. The kinetic and spectroscopic results are discussed in the context of previous kinetic studies of alkaline hydrolysis of alkyl 2,4‐dinitrophenyl ethers, recent 1H NMR spectroscopic studies of electron‐deficient aryl ethers and the mechanism of hydrolysis in the DNPEG systems. The possible significance of these results for the development of time‐release herbicide systems is cosidered briefly.