Size selective incorporation of gold nanoparticles in diblock copolymer vesicle wall

A systematic study is conducted to reveal how far the polymeric vesicle wall can embed gold nanoparticles (AuNPs) with different sizes by combining experiments and self-consistent field simulations. Both the experimental and simulative results indicate that the location of AuNPs in vesicle wall or in spherical micelle is heavily size dependent. Whether the AuNPs enter the vesicle wall or not is determined by a ratio of the diameter of AuNPs (D0) to the thickness of the vesicle wall (d(w0)). The 1-dodecanethiol-coated AuNPs (Au(x)R) with D0/d(w0) < 0.3 will stably disperse in the vesicle walls. For polystyrene-coated AuNPs (Au(x)S), a criterion of D0/d(w0) is proposed based on the phase diagram; i.e., the Au(x)S with D0/d(w0) < 0.5 can be located in the vesicle wall. Otherwise, the Au(x)R and the Au(x)S prefer to locate in spherical micelles. Moreover, the contributions of enthalpy and entropy to the total free energy of the system are respectively calculated to reveal the mechanism of the size selective distribution of AuNPs. The results demonstrate that the escape of AuNPs from vesicle walls and their selective distribution in spherical micelles is an entropy-driven process. Our study provides an important guideline for fabricating nanoparticle/block copolymer hybrid vesicles in dilute solution.