PRODAN and C120 fluorescent probes to investigate the structure of branched cyclic polyglycerol

• For the first time, the structure of bcPGs was studied using fluorescent probes. • A comparative study with different macro(molecules) allowed elucidate bcPG structure. • The polymer topology strongly influences the ability of PGs to host small molecules. Hyperbranched polyglycerols have been widely studied in biomedical applications due to their biocompatibility and chemical functionality. Branched cyclic polyglycerols, which have a cyclic structure in their central core, belong to the family of hyperbranched polyglycerols but have not been extensively explored. To better understand the potential of these novel polymers to host small molecules and to elucidate their complex structure, we proposed here the use of environmentally sensitive probes, PRODAN and Coumarin 120 (C120), which undergo changes in their fluorescence intensity and emission maxima in response to changes in the environment. To this end, the photophysical properties of both fluorescent dyes were studied in the presence of aqueous solutions of branched cyclic polyglycerol and a number of compositionally and structurally similar molecules and macromolecules, including hyperbranched polyglycerol, β-cyclodextrin, glycerol, and crown ethers such as 12-crown-4, 15-crown-5, 18-crown-6, and 2-hydroxymethyl 18-crown-6. PRODAN is able to accept hydrogen bonds and C120 is able to accept and donate hydrogen bonds. Consequently, the distinct photophysical response of PRODAN and C120 when interacting with the above molecules and macromolecules, rich in either hydroxyl or ether groups, provided valuable insights into the structure of branched cyclic polyglycerols and their ability to host small molecules.