Regulated Fragmentation of Crystalline Micelles of Block Copolymer via Monoamine-Induced Corona Swelling

Because long cylindrical crystalline micelles of block copolymers (BCPs) are similar to the fibril structures related to some severe diseases to some extent, study of the disassembly process of crystalline micelles of BCPs may provide some conceptual inspiration to the therapy of these diseases. Herein the effect of amines on the fragmentation of cylindrical crystalline-polyelectrolyte polyethylene-block-poly(acrylic acid) (PE-b-PAA) micelles is investigated. It is found that long crystalline cylindrical micelles (150-400 nm) can be fractured into short stublike ones (20-50 nm) by adding monoamines like diethylamine, triethylamine, and lysine, while addition of diamines such as ethylenediamine and 2,2′-(ethylenedioxy)di(ethylamine) or inorganic base like ammonia and sodium hydroxide has little effect on the morphology of cylindrical PE-b-PAA micelles. Fourier transform infrared (FT-IR) characterization shows that the interaction between PAA and amines is electrostatic attraction. The fragmentation of PE-b-PAA cylindrical micelles can be ascribed to the stress release of PAA corona chains swollen by amines, which is related to the effective functionality and molecular size of amines. Calculation of free energy verifies the thermodynamic accessibility of the fragmentation of PE-b-PAA cylindrical crystalline micelles induced by monoamines.