Block Copolymer-Directed Assembly of Nanoparticles:  Forming Mesoscopically Ordered Hybrid Materials

Thompson, Russell B.; Ginzburg, Valeriy V.; Matsen, Mark W.; Balazs, Anna C.

doi:10.1021/ma011563d

Cited by 291 publications

(326 citation statements)

References 35 publications

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“…This behavior has been experimen-tally documented by many authors and has been the subject of theoretical treatment. [12][13][14][15] While segregation of nanosized particles into specific domains of a multiphase system is reasonably understood, it remains still a puzzle what drives such particles to undergo reversible or irreversible association in a homogeneous polymer matrix. Theoretical treatments can be found in the recent literature for instance by Schweizer et al 16 and Balazs et al 17 However, experimental investigations that would allow to verify theoretical predictions are scarce and, in fact, difficult to obtain for the reason that suitable combinations of nanosized particles of precisely known surface properties and polymer matrices cannot be readily found.…”

Section: Introductionmentioning

confidence: 99%

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

et al. 2007

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Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO 3 H 2 ) in situ by monolayer coverage. Particle size and graft density of -PO 3 H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (φ) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 µm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm -1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm -1 vol % -1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ ) 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula. IntroductionThe development of polymer-based composites which exhibit various optical functionalities such as high/low refractive index, tailored absorption/emission properties, or strong optical nonlinearities attracts great interest because of the potential optoelectronic applications. 1,2 More specifically, it was pointed out that such composite materials could be applied as transparent substrate or flexible functional layers of optoelectronic devices which require high transparency in the visible range of the optical spectrum. 3 Replacing the conventional substrates made up of inorganic glasses by polymer-based materials could provide a number of advantages, as the polymer composites have milder processing conditions and better impact resistance, can be made flexible, and the optical parameters can be tailored. These composites are typically obtained by the incorporation of functional inorganic particles into a transparent polymer matrix. 3 While the polymeric component provides processability, flexibility, and transparency, the inorg...

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Section: Introductionmentioning

confidence: 99%

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

et al. 2007

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“…The radii of the p 1 and p 2 particles are denoted by R 1 and R 2 , respectively, and are given in units of R 0 , the root-meansquare end-to-end distance of the chain. These nanoparticles are comparable in size to the copolymers, and this correspondence of scales contributes to the unique structural organization within these nanocomposites.To determine the structure of the mixture, we now modify our previous SCF/DFT approach [8][9][10], which combines a self-consistent field theory (SCF) for diblocks with a density functional theory (DFT) for solid particles. The new free energy functional is…”

mentioning

confidence: 99%

“…To determine the structure of the mixture, we now modify our previous SCF/DFT approach [8][9][10], which combines a self-consistent field theory (SCF) for diblocks with a density functional theory (DFT) for solid particles. The new free energy functional is…”

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confidence: 99%

Entropically Driven Formation of Hierarchically Ordered Nanocomposites

et al. 2002

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Using theoretical models, we undertake the first investigation into the rich behavior that emerges when binary particle mixtures are blended with microphase-separating copolymers. We isolate an example of coupled self-assembly in such materials, where the system undergoes a nanoscale ordering of the particles along with a phase transformation in the copolymer matrix. Furthermore, the selfassembly is driven by entropic effects involving all the different components. The results reveal that entropy can be exploited to create highly ordered nanocomposites with potentially unique electronic and photonic properties. DOI: 10.1103/PhysRevLett.89.155503 PACS numbers: 81.07.Pr, 61.46.+w, 83.80.Uv The self-assembly of hard and soft components into nanostructured composites can facilitate the development of novel biomimetic [1], photonic [2], and electronic [3,4] materials. By themselves, binary mixtures of hard particles that differ in size or shape can self-assemble into a startling array of ordered structures [5,6]. Soft block copolymers can ''microphase separate'' into spatially periodic lamellar, cylindrical, spherical, or more complicated mesophases [7]. Using theoretical methods, in this Letter we conduct the first investigations into the cooperative behavior and novel structures that can potentially emerge when these two disparate ordering phenomena are coupled. Focusing on a small volume fraction of bidisperse spheres in AB diblocks, we isolate a system that simultaneously exhibits a structural change in the system of particles and a transformation in the microstructure of the copolymer matrix, creating in a single process a nanocomposite that potentially exhibits unique optoelectronic properties. Furthermore, these morphological changes are driven entirely by entropic effects involving all of the species. Our results indicate that the blending of particle mixtures and block copolymers can be exploited to create materials with new morphologies and functions.To characterize the diblocks in our system, we let f denote the fraction of A segments per chain. The enthalpic interaction between an A segment and a B segment is described by the dimensionless Flory-Huggins parameter, AB . Both the larger (referred to as p 1 ) and smaller (p 2 ) spheres are preferentially wetted by the A blocks. That is, the Flory-Huggins interaction parameter between the particles and A is taken as p1A p2A 0, and the interaction parameter between the different particles and the B species is set equal to AB ( AB p1B p2B). The radii of the p 1 and p 2 particles are denoted by R 1 and R 2 , respectively, and are given in units of R 0 , the root-meansquare end-to-end distance of the chain. These nanoparticles are comparable in size to the copolymers, and this correspondence of scales contributes to the unique structural organization within these nanocomposites.To determine the structure of the mixture, we now modify our previous SCF/DFT approach [8][9][10], which combines a self-consistent field theory (SCF) for diblocks with a density funct...

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“…We note that this calculation has been carried out for the case of rod-like particles and diblock copolymers 4 using our hybrid ''SCF/DFT'' model, which combines the self-consistent field (SCF) theory with density functional theory (DFT). 2,3,5,6 The homogeneous phase can be stable only if the free energy assumes a positive definite, quadratic form with respect to long wavelength density variations near the uniform state. This implies that the following three conditions must all be satisfied to guarantee the stability (or metastability) of the homogeneous phase; violation of any of these equations lead to phase separation.…”

Section: The Modelmentioning

confidence: 99%

“…This is particularly difficult when the additives are solid nanoparticles, which are typically introduced to impart or enhance a range of physical properties (e.g., optical, electrical, and mechanical). To provide guidelines for creating the desired mixtures, researchers have developed theoretical models for the equilibrium and dynamic behavior of mixtures of diblock copolymers and nanoparticles, [1][2][3][4][5][6][7][8] as well as models for the structural evolution of particle-filled binary blends. [9][10][11][12][13][14][15][16] However, there have as yet been few systematic theoretical studies on the thermodynamic properties of mix- To address the aforementioned issue, Ginzburg recently carried out a thermodynamic analysis to determine the influence of nanoparticles on the miscibility of blends of A and B homopolymers.…”

Section: Introductionmentioning

confidence: 99%

Determining the phase behavior of nanoparticle‐filled binary blends

Ginzburg

Balazs

2006

J Polym Sci B Polym Phys

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Nanoparticle additives provide a means of imparting the desired electrical, optical, or mechanical properties to a polymeric matrix. The difficulty faced in creating these composites is determining the optimal conditions for forming a thermodynamically stable mixture, where the particles will not phase separate from the matrix material. This challenge is even more daunting when the polymeric matrix is itself a multicomponent mixture, as is often the case in advanced materials. Ideally, the nanoparticles would not only contribute the needed physical properties, but also stabilize the mixture so that the entire system forms a single-phase system. In this study, we use a free energy expression for a binary blend that contains nanoparticles and take the interaction parameters between the different species to be independent variables. Thus, the particles can have distinct enthalpic interactions with each of the polymeric components. Using this expression, we determine the conditions under which the mixture forms a stable, single-phase material. In particular, we isolate how variations in the system's parameters (e.g., polymer composition, particle volume fraction, particle size, interaction energies) affect the phase diagrams. The findings provide guidelines for creating effective formulations and can allow researchers to understand how choices made in the nature of the components affect the overall macroscopic properties.

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Block Copolymer-Directed Assembly of Nanoparticles: Forming Mesoscopically Ordered Hybrid Materials

Cited by 291 publications

References 35 publications

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

Optical Properties of Composites of PMMA and Surface-Modified Zincite Nanoparticles

Entropically Driven Formation of Hierarchically Ordered Nanocomposites

Determining the phase behavior of nanoparticle‐filled binary blends

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