First poly(2-oxazoline)s with pendant amino groups

A new 2-oxazoline monomer with a Boc protected amino function, 2-[N-Boc-5-aminopentyl]-2-oxazoline; (Boc-AmOx), was synthesized from commercially available compounds. With an initiator salt system (N-methyl-2-methyl-2-oxazolinium triflate; MeOxOTf), the monomer could be converted via living cationic ring-opening polymerization to well-defined homopolymers with narrow molar mass distributions and targeted polymer chain length. After a quantitative deprotection, poly(2-oxazoline)s with pendant amino functions were obtained. In order to vary the polymer functional group density and solubility of the polymer, copolymerization with different monomer ratios of BocAmOx and 2-ethyl-2-oxazoline (EtOx) was performed. Exsitu NMR spectroscopy studies verified the randomness of the cationic copolymerization. The accessibility of the pendant amino side functions was confirmed in polymer analog thiourea formation with different isothiocyanates, such as benzyl isothiocyanate (BzNCS), or a fluorescence dye, tetramethyl rhodamine isothiocyanate (TRITC). A cross-linking reaction with a bifunctional isothiocyanate (Ph(NCS)₂) resulted in poly(2-oxazoline) hydrogels.