Bio-Based Amphiphilic Farnesyl Glycidyl Ether Block Copolymers: Aqueous Self-Assembly and Solubilization Boosting

Sustainability has become essential in addressing the substitution of depleting fossil-based resources with bio-renewable alternatives, including products active at interfaces, such as surfactants. Enhancing their efficiency reduces both ecological and economic impact. Here, we present amphiphilic poly(ethylene glycol)-b-poly(terpenyl glycidyl ether) diblock copolymers synthesized via anionic ring-opening polymerization from two terpenyl glycidyl ethers (TGE) based on the naturally occurring terpenoid farnesol, farnesyl glycidyl ether (FarGE), and its hydrogenated derivative hexahydrofarnesyl glycidyl ether (HHFarGE). Using poly(ethylene glycol) monomethyl ether (mPEG₁₁₄) as a macroinitiator resulted in controlled molecular weights (5600 - 8400 g·mol^-1) with low dispersities Đ (1.04-1.07). Fluorescence spectroscopy and light scattering revealed low critical micelle concentrations with a systematic decrease with increasing TGE block size due to the hydrophobic effect. The addition of small amounts of mPEG₁₁₄-b-PTGE_m to microemulsions leads to a significant increase of the solubilization efficiency not limited to conventional H₂O/NaCl - n-decane - tetraethylene glycol monodecyl ether microemulsions, but also in sustainable H₂O - isopropyl myristate - n-octyl β-D-glucopyranoside - farnesol formulations, serving as model systems for cosmetic applications. Using SANS, we observed that adsorption of the copolymer at the amphiphilic film leads to an increased structural order of bicontinuous microemulsions due to a higher film bending rigidity.