Amphiphilic polyoxazoline copolymers with carboxylic acid functionality via succinylation of poly(2-propyl-2-oxazoline-co-ethyleneimine)

Official URL: https://dx.doi.org/10.1016/j.mtchem.2026.103494

Succinylated polyoxazoline derivatives represent a promising platform for designing versatile pH-sensitive materials for applications in drug delivery, emulsification, and surface functionalization. In this study, we synthesized and characterized amphiphilic, carboxylic acid-functional polyoxazoline copolymers via the succinylation of partially hydrolyzed poly(2-propyl-2-oxazoline) (PPrOZ) with succinic anhydride. The partial hydrolysis of PPrOZ precursor enabled the introduction of reactive secondary amine groups through partial pendant group cleavage resulting in linear polyethyleneimine segments (L-PEI). These reactive sites were reacted with succinic anhydride to yield carboxylic acid-containing amphiphilic copolymers, denoted as succinylated poly(2-propyl-2-oxazoline-co-ethyleneimine), abbreviated as S-PPrOZ-PEI. The obtained polymers were characterized using 1H NMR, FTIR, and SEC, confirming both hydrolysis and succinylation. Buffering capacity was assessed by titration experiments, which revealed a pKa value of 4.53 and a buffering region between pH 3.5 and 5.5 for S-PPrOZ-PEI with further improvement upon addition of KH2PO4 salt. Water uptake measurements showed a significantly higher hydrophilicity, with an approximately fivefold increase in moisture content after 144 h for S-PPrOZ-PEI compared to PPrOZ. Moreover, in dip-coating experiments, up to 37% retention of S-PPrOZ-PEI polymer on non-woven (NW) polypropylene (PP) sheets was observed. Ultimately, NW PP sheet treated with S-PPrOZ-PEI in presence of KH2PO4 salt showed a maximum of 80% reduction in contact angle measurements compared to the blank NW PP substrate. These polymers are expected to serve as hydrophilic and pH-sensitive building blocks for the design of enhanced buffer systems and surface-active agents.