Amphiphilic nonionic block and gradient copoly(2-oxazoline)s based on 2-methyl-2-oxazoline and 2-phenyl-2-oxazoline...

Poly(2-alkyl/aryl-oxazoline)s (PAOx) have seen a resurgence of interest in the new millennium due to their biocompatibility, low toxicity, and higher tunability compared to poly(ethylene glycol)s (PEG)s. Due to the straightforward access to hydrophilic and hydrophobic PAOx, it was hypothesized that amphiphilic PAOx should be capable of stabilizing oil/water (O/W) interfaces. Furthermore, the control of their composition, chain length, and monomer distribution could suggest the formulation of tunable emulsions. Special emphasis was given to evaluate whether spontaneously formed amphiphilic gradient copolymer could stabilize O/W emulsions.

We prepared a series of amphiphilic block and gradient copolymers based on 2-methyl-2-oxazoline and 2-phenyl-2-oxazoline with variable hydrophilic/lipophilic balance, degree of polymerization, and monomer distribution as basis to explore their ability to stabilize emulsions. Systematic granulometry, stability, and rheology studies were performed to characterize the final emulsions.

Remarkably, stable O/W emulsions are obtained with only 0.5 wt% of copolymers. The finer emulsions stabilized by the most hydrophilic copoly(2-oxazoline)s allow an adjustment of their texture, as well as the concentration increase and oil content. Importantly, emulsion properties prepared with gradient copolymers show similar behavior compared with their block counterparts offering easy access to new biocompatible emulsifiers as these gradient copolymers are spontaneously formed by statistical copolymerization.