Encapsulation properties of reverse-amphiphilic core/shell polymeric nanoobjects with different shapes

Abstract

Reverse-amphiphilic core/shell polymeric nanoobjects (PNOs) with lamellar, cylindrical and spherical morphologies derived from poly(glycidyl methacrylate)-block-poly(n-butyl methacrylate) (PGMA-b-PnBMA) diblock copolymers were used as nanocapsules to encapsulate anionic hydrophilic dyes. Through the bulk self-assembly of PGMA-b-PnBMA with different compositions, bulk materials with different microphase-separated morphologies were obtained. Ammonium hydroxide was used to crosslink the epoxy groups in the PGMA domains and amine groups were simultaneously introduced into the PGMA domains. Then the bulk materials were dispersed in toluene to generate shaped PNOs. After quaternizing amine groups in the cores, shaped PNOs with electropositive hydrophilic cores and hydrophobic PnBMA hairs were obtained. These PNOs dispersed in toluene were used as nanocapsules to transfer calmagite, an anionic hydrophilic dye, from water into the cores. The encapsulation capacities of these shaped PNOs were evaluated by comparing the number loading ratios (mole number of dyes encapsulated per mole of PGMA-b-PnBMA diblock copolymer chains (n_d/n_p)). Spherical nanocapsules had the highest n_d/n_p owing to the large specific area of the interface between the cores and shells of the spherical PNOs. The n_d/n_p of the cylindrical nanocapsules was approximately half that of the spherical ones and a little higher than n_d/n_p of the lamellar ones. As well as having the ability to encapsulate hydrophilic dyes in organic solution, the spherical nanocapsules could also be used to effectively separate dyes with different charges and uniformly color PnBMA bulk materials.