Synthesis of amphiphilic block-type macromolecular brushes with cleavable pendant chains and fabrication of micelle-templated polymer nanocapsules

Abstract

Nanocapsules composed of cross-linked membranes and empty voids have found wide applications as drug delivery carriers, sensors and nanosized reactors. In this research, a new method for the fabrication of functional nanocapsules is proposed. Poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-(poly(tert-butyl methacrylate)-graft-poly(2-(dimethylamino)ethyl methacrylate)) (POEGMA-b-(PtBMA-g-PDMAEMA)) brush polymers were synthesized by two-step reversible addition–fragmentation chain transfer polymerization and atom transfer radical polymerization. The pendant PDMAEMA chains were grafted to the backbones through disulfide bonds. In acidic water, the brush polymer chains self-assembled into micelles with PtBMA cores and POEGMA/PDMAEMA mixed coronae. Upon cross-linking of PDMAEMA chains and cleavage of the disulfides with tri-n-butylphosphine, hydrophilic nanocapsules were obtained. The brush polymers were analyzed by gel permeation chromatography and ¹H NMR. The sizes and the morphologies of the micelles and the nanocapsules were characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The thiol groups on the inner walls of the nanocapsules undergo a thiol–ene reaction with fluorescein O-methacrylate (FMA). The photoluminescence results demonstrate that FMA molecules are able to pass through the membranes and functionalization of the nanocapsules can be performed.