However, the reaction also caused undesirable chain scissions from an intermediate radical or oxonium cation before they react with a nucleophilic carboxylic acid, resulting in decreased molecular weight and broadened dispersity of a number average molecular weight (Mn) of 3.6 kg/mol and dispersity (Đ) of 1.38. To balance activation and attachment rates, the TBHP loadings were decreased in subsequent experiments. At TBHP = 0.7 equiv., the conversion rate was 79%, and the functionalization ratio was 3.9 mol% (entry 2). The crude mixture showed nominal dispersity broadening and good conversion (Mn = 5.1 kg/mol, Đ = 1.23). After dialysis in acetone, the purified functional PEO had a functionalization ratio of 3.3 mol%, Mn = 5.5 kg/mol, and Ð = 1.29 (entry 2-1). The conversion rates decreased to 49% and 15% at TBHP loadings of 0.5 and 0.25 equiv., respectively (entries 3 and 4). The 1 H NMR and FT-IR spectra confirmed the successful introduction of the benzoyloxy group to PEO 6.0k (Figure ). Aromatic proton peaks of 2:1:2 ratio (7.30 -8.20 ppm, orange dot) and triplet acetal proton peak (6.25 ppm, red dot) in 1 H-NMR and an ester vibration signal (1720 cm -1 ) in FT-IR were placed with PEO signals.