2-phenyl-2-oxazoline and 2-methyl-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.

Topics: Emulsifying Agents; Emulsions; Oxazoles; Polymers

Solvent mixtures often alter the solubility of polymeric substances. Statistical copolymers made from 2-methyl-2-oxazoline (MeOx) and 2-phenyl-2-oxazoline (PhOx) are known for their varying solubilities in pure ethanol, pure water and in binary mixtures of ethanol-water. Constrained Molecular Dynamics (MD) simulations have been carried out with an aim to explain the varying solubilities of the statistical MeOx-PhOx copolymers. The solute-solvent dynamic friction kernels calculated through constrained MD simulations corroborate the solubility pattern in these copolymers. The solvation characteristics have been analyzed in terms of the solute-solvent radial distribution functions (RDFs). The ethanol-soluble MeOx-PhOx copolymers exhibit characteristic solute-composition dependence in the dynamic solute-solvent friction kernels, indicating the strength of the solute-solvent correlations. The aggressive solvation by the ethanol molecules in the binary solvent mixtures has been brought out by the O(solute)-H(ethanol) RDFs which exhibit a characteristic dependence on the ethanol content in the solvent composition. The corresponding O(solute)-H(water) RDFs are devoid of any such composition dependence. For all the MeOx-PhOx copolymers, the O-site solvation is strongly dominated by the water molecules and the N-sites are solvated equally by both ethanol and water molecules.

Topics: Ethanol; Molecular Dynamics Simulation; Oxazoles; Polymers; Solutions; Solvents; Water