Controlling the Self-Assembly Structure of Magnetic Nanoparticles and Amphiphilic Block-Copolymers: From Micelles to Vesicles

Abstract

We report how to control the self-assembly of magnetic nanoparticles and a prototypical amphiphilic block-copolymer composed of poly(acrylic acid) and polystyrene (PAA-b-PS). Three distinct structures were obtained by controlling the solvent-nanoparticle and polymer-nanoparticle interactions: (1) polymersomes densely packed with nanoparticles (magneto-polymersomes), (2) core-shell type polymer assemblies where nanoparticles are radially arranged at the interface between the polymer core and the shell (magneto-core shell), and (3) polymer micelles where nanoparticles are homogeneously incorporated (magneto-micelles). Importantly, we show that the incorporation of nanoparticles drastically affects the self-assembly structure of block-copolymers by modifying the relative volume ratio between the hydrophobic block and the hydrophilic block. As a consequence, the self-assembly of micelle-forming block-copolymers typically produces magneto-polymersomes instead of magneto-micelles. On the other hand, vesicle-forming polymers tend to form magneto-micelles due to the solubilization of nanoparticles in polymer assemblies. The nanoparticle-polymer interaction also controls the nanoparticle arrangement in the polymer matrix. In N,N-dimethylformamide (DMF) where PS is not well-solvated, nanoparticles segregate from PS and form unique radial assemblies. In tetrahydrofuran (THF), which is a good solvent for both nanoparticles and PS, nanoparticles are homogeneously distributed in the polymer matrix. Furthermore, we demonstrated that the morphology of nanoparticle-encapsulating polymer assemblies significantly affects their magnetic relaxation properties, emphasizing the importance of the self-assembly structure and nanoparticle arrangement as well as the size of the assemblies.

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…8). 232 Depending on the initial casting solvent, stable core-shell structures, micelles, or particle-loaded polymersomes were observed in water. Clearly, the initial solvent plays a dominant role on the final structure, but there is no means to anticipate these structures without performing experiments.…”

Self-assembly and morphology transition of amphipathic spiropyran-based random copolymers to control drug release

“…In recent years, a great deal of stimuli-responsive amphipathic polymer micelles that respond to internal or external stimuli including pH, [1,2] temperature, [3] redox, [4] light, [5], and magnetic field [6] have been abundantly investigated due to their broad range of potential applications as nanocarriers, [7] biosensors, [8,9], and biochemical gates. [10] Among the various stimuli, light is one of the most attractive external stimuli because of the superiority in spatial and temporal control.…”

Advanced functional nanomaterials with microemulsion phase

“…The rearrangement of polymeric micelles indicates that pluronics do not simply perform as a template in synthesizing nanoparticles of different morphologies, as stated in the previous literature [65]. Also, the incorporation of metal ions and production of nanoparticles promote a morphological transition of the block copolymers, which has been utilized to induce polymer vesicle formation [66]. This approach provides an economic way to synthesize gold nanoparticles with high stability under various physicochemical conditions, which exhibits great opportunities to be used in biotechnology and biomedicine [67].…”