Self-assembly of cetyl linear polyethylenimine to give micelles, vesicles, and dense nanoparticles

The involvement of macromolecules in the formation of biological and other membranes has important implications for structural biology and nanoengineering. Using cetyl polyethylenimines of varying molecular weight and hydrophobicity, it was found that polymer hydrophobicity (mol % cetylation) controlled the nature of the self-assembly, giving micellar (cetyl groups < 23 mol %), vesicular (cetyl groups = 23−42 mol % or cetyl groups = 3−42 mol % with cholesterol), and dense nanoparticle (cetyl groups ≥ 49 mol %) aggregates. Thick (up to 15 nm) membranes due to the polyelectrolyte coating with the amphiphile were observed with low levels of cetylation only, and both dn/dc (indirectly) and vesicle/nanoparticle size (directly) varied linearly with mol % cetylation (r = 0.96−0.99).