Abstract
Summary: Two series of novel α,ω‐perfluoroalkyl terminated esters of poly(ethylene oxide) (PEO) (R~F~‐PEO) having the general structure C~m~F~2__m__+1~COO(CH~2~CH~2~O)~n~OCC~m~F~2__m__+1~, with m = 1,2,3,4 or 5 have been synthesized. The influences of the PEO molar mass, the length of the perfluoroalkyl group (R~F~) and temperature on the cleavage of the ester bridge in aqueous solution and the effect of the hydrolysis process on the size of aggregates formed in water were studied. According to ^1^H and ^19^F NMR measurements the degree of functionalization obtained (up to 96 mol‐%) increases with the decrease in the length of the R~F~ group. All of the derivatives showed ester cleavage in water in short time scales. The rates of hydrolysis of the ester bridge in aqueous solution were determined from pH‐measurements. It was verified that the rate law for hydrolysis corresponds to a pseudo‐first order type. The hydrolysis kinetic constant k increased with a decrease in the length of the R~F~ group ranging from 0.2 × 10^−3^ s^−1^ for the longest R~F~ group (C~5~F~11~) up to 1.2 × 10^−2^ s^−1^ for the shortest R~F~ group (CF~3~). The value of k depended almost exclusively on the length of the perfluoroalkyl chain and was independent of the length of the PEO backbone (1 000 or 2 000 g · mol^−1^), as long as no additional phenomenon such as phase separation was present. It was also found that the change in the value of k with temperature followed a non‐Arrhenius pattern and there was an evident relationship between the non‐linearity in the ln k vs. 1/T relation with increasing temperatures and the occurrence of a macroscopic phase separation of LCST type. Dynamic light scattering measurements showed the coexistence of unimers with associated species with apparent hydrodynamic radii (R~h~) of approximately 20–45 nm for all samples in aqueous solutions. These species might correspond to aggregates of a few micelles. For some samples also larger aggregates were found with R~h~ in the 100–500 nm range, which might be attributed to clusters of micelles.
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