Ordering of Gold Nanorods in Confined Spaces by Directed Assembly

Abstract

This paper describes an effective approach to order gold nanorods (NRs) within cylindrically confined microdomains of block copolymer-(BCP-) based supramolecular assemblies. Individual BCP micelles encapsulated with wellordered NRs can be obtained by disassembling the supramolecular structures. The mismatch of binary polymer brushes with different lengths on the surface of the NRs was used to effectively improve the dispersion of the NRs within polymer matrix, due to enhanced wetting of the brushes by surrounding mismatch polymers. This enables us to quantitatively explore the location and orientation of the NRs within confined geometries. By varying the content of NRs, the aspect ratio of the NRs, or the diameter of the cylindrical BCP micelles, the orientation of the NRs within micelles can be tuned to form one-dimensional nanostrings with end-to-end organization of NRs along the micelles or with side-by-side twisted arrangement of NRs perpendicular to the micelles. UV−vis spectroscopy measurements and finitedifference time-domain (FDTD) calculations confirm that our approach provides a simple yet versatile route to tune the optical properties of the hybrid micelles by controlling the ordering of the NRs. This work provides guidelines for dispersing other functional anisotropic NPs, and lays groundwork for the fabrication of optical and electronic devices.

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory

“…22,23 Perhaps the simplest small anisotropic objects are nanorods, and their behavior in block copolymer films has been considered in Refs. [24][25][26][27][28][29][30][31][32][33][34][35][36], which are mainly short communications just focused into the visualization of the morphology of the prepared composites. In any case the number of 4 publications dealing with anisotropic nanoparticles in block copolymers is vanishingly small compared with the total number of publications on block copolymer nanocomposites over the past decade.…”

End-to-End Alignment of Nanorods in Thin Films

“…BCPbased supramolecules are effective in this as well. 38,39 Geometric confinement imposed by the supramolecular framework leads to NR assembly in bulk. In cylindrical supramolecular nanocomposites, the high aspect ratio NRs are selectively sequestered at the interstitial sites between the BCP cylinders.…”

Aspect ratio effect of nanorod surfactants on the shape and internal morphology of block copolymer particles

“…[12][13][14][15][16] Despite their interesting and attractive properties, much fewer studies on the morphological behavior of BCP/NR assembly have been conducted when compared with BCP/NP system. 6,[17][18][19][20][21][22] The influence of the AR values of the NRs on their positioning in the BCP domain and on their morphological behavior has been theoretically simulated; [23][24][25] however, it is still an open question experimentally. Although the assembly of NPs in BCP domains can be relatively well understood by the interplay of entropy loss of the chains to accommodate the NPs and enthalpic interactions between the NPs and BCPs, 26,27 other factors including the anisotropic geometry, rotational freedom, and NR-NR interactions should be considered for the NR positioning within the BCP domains.…”

“…33 In addition, highly anisotropic NRs often tend to aggregate side-by-side due to the rod-rod interactions, which could reduce the efficiency of NRs as surfactants to generate the morphological transition of the BCP particles. 6,7 FIGURE 3 SEM and TEM images of PS 27k -b-P4VP 7k (PDP) 0.5 particles including (a and b) NR-1, (c and d) NR-6, and (e and f) NR-15; NR-1 and NR-15 generated spherical particles, whereas NR-6 produced convex lens-shaped particles. We observed a dramatic morphological transition of the BCP particles from spherical to the convex lens-shaped particles; however, as the AR values of the NRs further increased, they became spherical again.…”

“…[1][2][3][4] This is of particular interest in the case of anisotropically shaped nanorods (NRs), because the collective electrical and optical properties of their organizations depend strongly on both their aspect ratio (AR) and directional assembly. [5][6][7][8][9][10][11] Self-assembly of block copolymers (BCPs) can direct the position of the NRs, their orientation, and three-dimensional assembly. [12][13][14][15][16] Despite their interesting and attractive properties, much fewer studies on the morphological behavior of BCP/NR assembly have been conducted when compared with BCP/NP system.…”