Synthesis and Characterization of Oligo(Ethylene Glycol)s Functionalized with Desaminotyrosine or Desaminotyrosyltyrosine

Abstract

The aromatic compounds desaminotyrosine (DAT) and desaminotyrosyltyrosine (DATT) have been successfully used to functionalize gelatin in order to form physically crosslinked networks via π-π interactions and hydrogen bonds of the introduced phenol moieties. Here, it was explored whether this concept can be applied to a synthetic polymer not engaging in additional interactions such as triple helix formation in gelatin, enabling a network to form by physical interactions mainly related to the terminal functional groups. Oligo(ethylene glycol) (OEG) was chosen as hydrophilic synthetic polymer for the backbone structure. Linear OEG (MP = 3 kDa) and four-arm OEG (Mn = 5 kDa) with amino functionalities as endgroups were functionalized with DAT and DATT using EDC·HCl and NHS as activating agents. The compounds were characterized by NMR, IR spectroscopy, and MALDI. Rheological behavior of aqueous solutions of the polymers was studied. The critical micelle concentration (CMC) was determined by a fluorescence spectroscopic analysis using the hydrophobic fluorescent dye pyrene. DATT-functionalized linear OEG, four-arm DAT-functionalized OEG and four-arm DATT-functionalized OEG were synthesized with degrees of functionalization of 60-95 mol%. All compounds were water soluble, and rheological measurements revealed a decrease in storage modulus G' and loss modulus G'' compared to unfunctionalized OEG. Moreover, the CMC of linear OEG-DATT could be determined. The syntheses of OEG functionalized with the aromatic compounds DAT and DATT was reported. The polymers showed the properties of a surfactant.