Composition-dependent sol-gel transition of amphiphilic blend of PEG with hydrophobic gallamide components

Two types of poly(ethylene glycol) (PEG)-based amphiphiles were synthesized: a diblock-type amphiphile (PEG1) with a hydrophobic moiety on one terminal of PEG (PEG with the molecular weight of 2000), and a triblock-type amphiphile (PEG2) with hydrophobic moieties on both terminals of PEG. The hydrophobic moiety consisted of hydrophobic C₁₄ alkyl tails covalently linked through a gallamide component. The sol–gel transitions of the aqueous solution of PEG1 and PEG2 were studied. At the PEG amphiphile concentration of 15 wt %, PEG1 gave a clear solution over a wide temperature range from 20 to 80 °C, while PEG2 was partially soluble in water. However, the aqueous blend solution of PEG1 and PEG2 exhibited a hydrogel depending on the blend ratio and temperature. It was considered that the composition of PEG1 and PEG2 governed the sol–gel transition, and that the dynamic moduli could be effectively controlled by changing the mixing ratios of the PEG amphiphiles.