Abstract
The cooperative self-assembly of nanoparticles and amphiphilic block copolymers has attracted increasing interests as it offers effective routes to achieve nanocomposite supramolecular structures with desired structure and properties. The incorporation of nanoparticles usually tunes the self-assembly structure of block copolymers, as the copolymer–nanoparticle interactions may change the relative volume ratio of hydrophobic block/hydrophilic block copolymers. It should be noted that the micro-size length and the strong nonpolar feature of carbon nanotubes (CNTs) may cause the block copolymer–CNT interactions to differ from the the block copolymer–nanoparticle interactions. Herein, we show that the diameter of CNTs and the copolymer/CNT ratio have a profound effect on the self-assembly behavior of amphiphilic block copolymers. Upon the addition of carboxylated multi-walled carbon nanotubes (c-MWCNTs, diameter <8 nm,) to the methoxy polyethylene glycol-poly (D,L-lactic acid) (MPEG-PDLLA) solution, it is difficult to observe the c-MWCNTs directly in TEM images. However, it has been found that they form supramolecular nanocomposite structures with MPEG-PDLLA. Moreover, these supramolecular structures transform from core–shell spherical micelles into rod-like micelles and then into large composite aggregates with the increase of the c-MWCNT addition. However, in the case of the addition of c-MWCNTs with a diameter of 30–50 nm, the dispersed c-MWCNTs and spherical core–shell micelles could be observed simultaneously in the TEM images at a low c-MWCNT addition, and then the micelle structure disappeared and only well-dispersed c-MWNTs were observed in TEM images at a high c-MWCNT addition. A possible model was proposed to explain the rule of CNTs participating in the formation of copolymer/CNT nanocomposite structures. It was also shown that as-prepared copolymer/CNT supramolecular nanocomposites could be used as drug carriers, enabling the adjustment of the drug loading and release time.
Highlights
The self-assembly of amphiphilic block copolymers offers a powerful route to enable the precise fabrication of multifunctional nanostructures [1–6]
To investigate the effects of different amounts of c-MWCNTs on the structure of MPEG-PDLLA/c-MWCNT nanocomposites, we fixed the concentration of MPEG-PDLLA at 1.5 mg/mL, which is above the critical micelle concentration, and the mass ratios of c-MWCNTs relative to MPEG-PDLLA were 0, 0.005:1, 0.01:1, 0.02:1, 0.05:1 and 0.1:1, respectively
MPEG-PDLLA/carbon nanotubes (CNTs) nanocomposites and it can be seen from these images that the addition of c-MWCNTs has a great influence on the morphology of nanocomposites
Summary
The self-assembly of amphiphilic block copolymers offers a powerful route to enable the precise fabrication of multifunctional nanostructures [1–6] These self-assembled nanostructures have been extensively studied and used for a range of biomedical applications including bioimaging and controlled drug delivery [7–9]. These nanocomposites can combine the advantages of both components (nanoparticles and amphiphilic block copolymers) and show some new and interesting properties that can be used as nanocarriers for biomedical applications. The incorporation of nanoparticles in self-assembled amphiphilic block copolymers can produce an interaction between nanoparticles and block copolymers that may have a significant impact on the hydrophobic interaction of hydrophobic blocks and the relative ratios of hydrophobic blocks/hydrophilic blocks The change in these parameters caused by the interaction between nanoparticles and block copolymers can affect the self-assembly behaviors and be used to adjust the structures and properties of nanocomposite supramolecular structures [15]
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