Aggregation behavior in water of amphiphilic diblock copolymers bearing biocompatible phosphorylcholine and cholesteryl groups

Poly(2-(methacryloyloxy) ethyl phosphorylcholine)-block-poly(cholesteryl 6-methacryloyloxyhexanoate) (PMPC82-b-PChM(n)) copolymers with different PChM block lengths were prepared via reversible addition-fragmentation chain transfer controlled/living radical polymerization using a PMPC-based macro-chain transfer agent. The subscript number and n (= 3 and 6) refer to the degree of polymerization of the PMPC and PChM blocks, respectively. PMPC82-b-PChM(n) cannot dissolve in water directly due to the strong hydrophobic nature of the PChM block. To prepare the aqueous solution, the diblock copolymer was dissolved in an organic solvent and then dialyzed against pure water. These diblock copolymers formed spherical and rod-like micelles in water, depending on the composition of cholesteryl (Chol) group in the polymer. The prepared aggregates were characterized using static light scattering, dynamic light scattering, transmission electron microscopy and fluorescence probe techniques. The characterization results suggest that the morphology of the polymer aggregates can be controlled from spherical to rod-like micelles by increasing the number of Chol groups in the polymer.