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A general route to nanocrystal kebabs periodically assembled on stretched flexible polymer shish.

Xu H, Xu Y, Pang X, He Y, Jung J, Xia H, Lin Z - Sci Adv (2015)

Bottom Line: However, this is an area where progress has been slower.These nanostructures can be regarded as organic-inorganic shish-kebabs, in which nanodisc kebabs are periodically situated on a stretched polymer shish.Simulations based on self-consistent field theory reveal that the formation of organic-inorganic shish-kebabs is guided by the self-assembled elongated star-like diblock copolymer constituents constrained on the highly stretched polymer chain.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. ; State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

ABSTRACT
Assembling nanoparticles into one-dimensional (1D) nanostructures with precisely controlled size and shape renders the exploration of new properties and construction of 1D miniaturized devices possible. The physical properties of such nanostructures depend heavily on the size, chemical composition, and surface chemistry of nanoparticle constituents, as well as the close proximity of adjacent nanoparticles within the 1D nanostructure. Chemical synthesis provides an intriguing alternative means of creating 1D nanostructures composed of self-assembled nanoparticles in terms of material diversity, size controllability, shape regularity, and low-cost production. However, this is an area where progress has been slower. We report an unconventional yet general strategy to craft an exciting variety of 1D nanonecklace-like nanostructures comprising uniform functional nanodiscs periodically assembled along a stretched flexible polymer chain by capitalizing on judiciously designed amphiphilic worm-like diblock copolymers as nanoreactors. These nanostructures can be regarded as organic-inorganic shish-kebabs, in which nanodisc kebabs are periodically situated on a stretched polymer shish. Simulations based on self-consistent field theory reveal that the formation of organic-inorganic shish-kebabs is guided by the self-assembled elongated star-like diblock copolymer constituents constrained on the highly stretched polymer chain.

No MeSH data available.


Related in: MedlinePlus

Formation mechanisms of (A) spherical nanoparticle and (B) 1D nanonecklace.The growth of Fe3O4 nanonecklace was taken as an example in (B). The formation of Fe3O4 nanonecklace underwent the coordination interaction between the precursors and amphiphilic star-like PAA-b-PS diblock copolymer constituents, followed by the hydrolysis and condensation reaction at elevated temperature to yield Fe3O4 nanonecklace.
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Figure 4: Formation mechanisms of (A) spherical nanoparticle and (B) 1D nanonecklace.The growth of Fe3O4 nanonecklace was taken as an example in (B). The formation of Fe3O4 nanonecklace underwent the coordination interaction between the precursors and amphiphilic star-like PAA-b-PS diblock copolymer constituents, followed by the hydrolysis and condensation reaction at elevated temperature to yield Fe3O4 nanonecklace.

Mentions: A variety of spherical colloidal nanoparticles have been synthesized by using star-like unimolecular micelle as template prepared from a β-CD core (30). It is not surprising that, by extension, using 1D micellar structures as template, anisotropic nanocrystals may be created, which is highly desirable because their physicochemical properties are often more interesting and unique than those of isotropic nanoparticles for many technological applications (36). Here, amphiphilic worm-like micelles rationally designed and synthesized were exploited as template to create surprising nanodiscs. It is obvious that the use of an amphiphilic star-like PAA-b-PS diblock copolymer (37) as template would lead to the formation of spherical nanoparticles (Fig. 4A). In stark contrast, in an amphiphilic worm-like PAA-b-PS diblock copolymer template, both PAA and PS chains cannot retain their spherical random coil-like conformation as in star-like PAA-b-PS diblock copolymer because all PAA-b-PS chains were confined on the PEG chain through the threaded α-CDs (that is, attached by one end). Moreover, because there were a number of α-CDs threaded on the PEG stem, PAA-b-PS chains grown from one α-CD core had to stretch out to alleviate the unavoidable steric crowding from the chains grafted from the neighboring α-CD core. These PAA-b-PS chains can be regarded as brushes. The interplay of the steric repulsion between adjacent α-CD–threaded PAA-b-PS brushes on the stretched PEG chain and the high density of threaded PAA-b-PS brushes on an individual α-CD (18 chains total) caused the energetically favored periodic separation of each α-CD–based PAA-b-PS brush. This explains why by capitalizing on amphiphilic worm-like PAA-b-PS diblock copolymers as nanoreactors, instead of continuous nanorods or nanowires, nanonecklaces were achieved despite the fact that a large amount of α-CDs were added in the reaction in an attempt to improve their threading density (Fig. 4B). Such high density of PAA-b-PS brushes constrained on the PEG was also responsible for forming stretched PEG chain despite the flexible nature of PEG. Together, each individual constituent of nanonecklace [that is, the 18-arm star-like PAA-b-PS diblocks connected to each α-CD (lower left panel in Fig. 1)] squeezed and extended perpendicularly with respect to the PEG stem, thereby forming elongated PAA-b-PS diblock copolymers (ellipsoid-shaped) of an α-CD rather than spherical shape, which in turn resulted in straight nanonecklaces consisting of periodic nanodiscs (that is, distorted rather than spherical nanoparticles) (Fig. 4B). To gain insight into the formation mechanism of nanonecklaces, we invoked the SCFT, a powerful method for solving the equilibrium problem, to calculate the self-assembly of star-like diblock copolymers threaded in the flexible yet highly stretched PEG chain, as elaborated later.


A general route to nanocrystal kebabs periodically assembled on stretched flexible polymer shish.

Xu H, Xu Y, Pang X, He Y, Jung J, Xia H, Lin Z - Sci Adv (2015)

Formation mechanisms of (A) spherical nanoparticle and (B) 1D nanonecklace.The growth of Fe3O4 nanonecklace was taken as an example in (B). The formation of Fe3O4 nanonecklace underwent the coordination interaction between the precursors and amphiphilic star-like PAA-b-PS diblock copolymer constituents, followed by the hydrolysis and condensation reaction at elevated temperature to yield Fe3O4 nanonecklace.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643824&req=5

Figure 4: Formation mechanisms of (A) spherical nanoparticle and (B) 1D nanonecklace.The growth of Fe3O4 nanonecklace was taken as an example in (B). The formation of Fe3O4 nanonecklace underwent the coordination interaction between the precursors and amphiphilic star-like PAA-b-PS diblock copolymer constituents, followed by the hydrolysis and condensation reaction at elevated temperature to yield Fe3O4 nanonecklace.
Mentions: A variety of spherical colloidal nanoparticles have been synthesized by using star-like unimolecular micelle as template prepared from a β-CD core (30). It is not surprising that, by extension, using 1D micellar structures as template, anisotropic nanocrystals may be created, which is highly desirable because their physicochemical properties are often more interesting and unique than those of isotropic nanoparticles for many technological applications (36). Here, amphiphilic worm-like micelles rationally designed and synthesized were exploited as template to create surprising nanodiscs. It is obvious that the use of an amphiphilic star-like PAA-b-PS diblock copolymer (37) as template would lead to the formation of spherical nanoparticles (Fig. 4A). In stark contrast, in an amphiphilic worm-like PAA-b-PS diblock copolymer template, both PAA and PS chains cannot retain their spherical random coil-like conformation as in star-like PAA-b-PS diblock copolymer because all PAA-b-PS chains were confined on the PEG chain through the threaded α-CDs (that is, attached by one end). Moreover, because there were a number of α-CDs threaded on the PEG stem, PAA-b-PS chains grown from one α-CD core had to stretch out to alleviate the unavoidable steric crowding from the chains grafted from the neighboring α-CD core. These PAA-b-PS chains can be regarded as brushes. The interplay of the steric repulsion between adjacent α-CD–threaded PAA-b-PS brushes on the stretched PEG chain and the high density of threaded PAA-b-PS brushes on an individual α-CD (18 chains total) caused the energetically favored periodic separation of each α-CD–based PAA-b-PS brush. This explains why by capitalizing on amphiphilic worm-like PAA-b-PS diblock copolymers as nanoreactors, instead of continuous nanorods or nanowires, nanonecklaces were achieved despite the fact that a large amount of α-CDs were added in the reaction in an attempt to improve their threading density (Fig. 4B). Such high density of PAA-b-PS brushes constrained on the PEG was also responsible for forming stretched PEG chain despite the flexible nature of PEG. Together, each individual constituent of nanonecklace [that is, the 18-arm star-like PAA-b-PS diblocks connected to each α-CD (lower left panel in Fig. 1)] squeezed and extended perpendicularly with respect to the PEG stem, thereby forming elongated PAA-b-PS diblock copolymers (ellipsoid-shaped) of an α-CD rather than spherical shape, which in turn resulted in straight nanonecklaces consisting of periodic nanodiscs (that is, distorted rather than spherical nanoparticles) (Fig. 4B). To gain insight into the formation mechanism of nanonecklaces, we invoked the SCFT, a powerful method for solving the equilibrium problem, to calculate the self-assembly of star-like diblock copolymers threaded in the flexible yet highly stretched PEG chain, as elaborated later.

Bottom Line: However, this is an area where progress has been slower.These nanostructures can be regarded as organic-inorganic shish-kebabs, in which nanodisc kebabs are periodically situated on a stretched polymer shish.Simulations based on self-consistent field theory reveal that the formation of organic-inorganic shish-kebabs is guided by the self-assembled elongated star-like diblock copolymer constituents constrained on the highly stretched polymer chain.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. ; State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

ABSTRACT
Assembling nanoparticles into one-dimensional (1D) nanostructures with precisely controlled size and shape renders the exploration of new properties and construction of 1D miniaturized devices possible. The physical properties of such nanostructures depend heavily on the size, chemical composition, and surface chemistry of nanoparticle constituents, as well as the close proximity of adjacent nanoparticles within the 1D nanostructure. Chemical synthesis provides an intriguing alternative means of creating 1D nanostructures composed of self-assembled nanoparticles in terms of material diversity, size controllability, shape regularity, and low-cost production. However, this is an area where progress has been slower. We report an unconventional yet general strategy to craft an exciting variety of 1D nanonecklace-like nanostructures comprising uniform functional nanodiscs periodically assembled along a stretched flexible polymer chain by capitalizing on judiciously designed amphiphilic worm-like diblock copolymers as nanoreactors. These nanostructures can be regarded as organic-inorganic shish-kebabs, in which nanodisc kebabs are periodically situated on a stretched polymer shish. Simulations based on self-consistent field theory reveal that the formation of organic-inorganic shish-kebabs is guided by the self-assembled elongated star-like diblock copolymer constituents constrained on the highly stretched polymer chain.

No MeSH data available.


Related in: MedlinePlus