Tuning the Thermo-Sensitivity of Micellar Systems through a Blending Approach

This paper reports an original and easy route toward thermosensitive micelles based on a lipidic core and with adjustable cloud point temperatures (T-CP) through a simple blending approach between two copolymers of different T-CP. The cationic ring-opening polymerization (CROP) of various 2-alkyl-2-oxazoline monomers was first investigated from both mesylated and tosylated lipoinitiators and different lipid-b-poly(2-methyl-2-oxazoline), lipid-b-poly(2-ethyl-2-oxazoline), lipid-b-poly(2-isopropyl-2-oxazoline) and lipid-b-poly((2-ethyl-2-oxazoline)-co-(2-isopropyl-2-oxazoline)) copolymers were synthesized. Blending of lipid-b-p(EtOx) and lipid-b-p(iPrOx) copolymers in various proportions were then prepared and their T-CP investigated through UVvisible spectroscopy. Very interesting results were obtained as the blends exhibit a single T-CP ranging from 35 to 45 degrees C. Furthermore, the blends T-CP correspond to those of the statistical lipid-b-p((EtOx)-co-(iPrOx)) for the same p(EtOx)/p(iPrOx) content up to 52 wt % of p(EtOx). The blending approach is then an attractive strategy to control the T-CP of micellar systems through a simple and easy formulation approach rather than fastidious syntheses.