Nanoparticle-regulated phase behavior of ordered block copolymers (original) (raw)
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Nanoparticle Ordering via Functionalized Block Copolymers in Solution
ACS Nano, 2008
We consider nanoparticles and functionalized copolymers, block copolymers with attached end groups possessing a specific affinity for nanoparticles, in solution. Using molecular dynamics, we show that nanoparticles are able to direct the self-assembly of the polymer/ nanoparticle composite. We perform a detailed study for a wide range of nanoparticle sizes and concentrations. We show that the nanoparticles order in a number of distinct phases: simple cubic, layered hexagonal, hexagonal columnar, gyroid, and a novel square columnar. Our results show that nanoparticles ordered with functionalized block copolymers can provide a simple and efficient tool for assembling novel materials with nanometer scale resolution.
Block Copolymer-Directed Assembly of Nanoparticles: Forming Mesoscopically Ordered Hybrid Materials
Macromolecules, 2002
Mixtures of diblock copolymers and nanoscopic spherical particles can yield well-ordered hybrid materials, which can be used for separation processes, catalysis, and optoelectronic applications. Predicting the morphologies of these systems is difficult because the final structures depend not only on the characteristics of the copolymer but also on the features of the particles. Combining self-consistent field and density functional theories, we develop a model that allows us to determine the equilibrium or metastable phases of diblock copolymer/spherical nanoparticle composites, without making a priori assumptions about the structure of the system. Using this model, we illustrate various examples where mixtures of diblocks and nanoparticles self-assemble into mesoscopically ordered phases. The model can be generalized to other types of copolymers and particles and can be modified to include homopolymers or solvent molecules. Thus, the technique constitutes a useful tool for determining the structures of a large class of nanocomposites. † University of Pittsburgh. ‡ Present address: The Dow Chemical Company,
Macromolecules, 2006
Introduction. Controlled ordering of nanoparticles in block polymer matrices has been exploited to synthesize novel composites for a variety of applications such as catalysis, semiconductors, photonic materials, electricity, and biological and medical fields. 1-3 Recently, a novel strategy 4-7 has been developed to organize nanoparticles in polymer matrices with controlled patterns by exploiting microphase separation of block copolymers, and it is observed that the confinement of nanoparticles in organized patterns improves the optical 8,9 and mechanical properties 10 of the nanocomposites. To gain better insight into the physical properties of these functional materials, significant effort is being devoted to understanding the morphologies of nanocomposites both theoretically and experimentally. Since solvent selectivity is an important parameter that determines the phase behavior of block copolymer solutions, its role has to be considered in solution-based synthetic routes for tailoring morphologies of nanocomposites. It has been found that order-disorder (ODT) and order-order (OOT) transition temperatures are correlated to the polymer concentration in solution, and the composition profiles and dimensions of microdomains vary with dilution. In a selective solvent, the solvent expands only the favorable block, causing shifts along both temperature and composition directions in the phase diagram. Effects similar to this can also be obtained by sequestering nanoparticles in the favorable domain. By using solvents with different selectivity and concentration of polymer and nanoparticles, it would be possible to tune the morphologies in the microdomains and consequently the nanocomposites.
Controlling the phase behavior of block copolymers via sequential block growth
Polymer, 2010
Block copolymers remain one of the most extensively investigated classes of polymers due to their abilities to self-organize into various nanostructures and modify polymer/polymer interfaces. Despite fundamental and technological interest in these materials, only a handful of experimental phase diagrams exist due to the laborious task of preparing such diagrams. In this work, two copolymer series are each synthesized from a single macromolecule via sequential living anionic polymerization to yield molecularly asymmetric diblock and triblock copolymers systematically varying in composition. The phase behavior and morphology of these copolymers are experimentally interrogated and quantitatively compared with predictions from mean-field theories, which probe copolymer phase behavior beyond current experimental conditions.
Block copolymer nanostructures
Nano Today, 2008
Block copolymers occupy a huge area of research because they offer a vast range of possibilities for architecture, size, and chemical composition. Advances in polymer chemistry 1 , such as anionic polymerisation 2 and most recently living radical polymerization 3 , have enabled a vast array of block copolymers to be synthesized with great control over their architecture, molecular weight, chemical composition, and functionality. Their intrinsic multi-properties allow the combination of different polymers and therefore the design of novel materials potentially comprising several different properties (e.g. thermoplastic, rubber, ductile, electrical conductivity, etc.). In bulk, when the different blocks are chemically immiscible, the balance between the entropically and enthalpically driven phase separation and the chemical bond constraints between the blocks drives the formation of ordered domains 4-10 . In solution, the interactions between the solvent and the different blocks dictate the ability to form well-defined structures. The architecture, molecular weight, volume fractions of blocks, and chemical functionality can all be set in the synthesis, making designer block copolymers a reality. The ability to effectively design nanoparticles and nanostructures to your preference, coupled with the wide range of applications associated with them, have made them an incredibly popular topic of research. Herein,
Compositional Dependence of the Order-Disorder Transition in Diblock Copolymers
Macromolecules, 1994
The bulk morphologies and microphase separation behavior were studied in seven low molecular weight poly(styrene-co-isoprene) diblock copolymers with polystyrene volume fractions ranging from 0.21 to 0.76. Their order-disorder transitions (ODT) were investigated using small-angle X-ray scattering and rheological measurements as a function of the degree of polymerization (N), composition, and temperature. The resultant versus composition plot has been compared with theories for the ODT in diblock copolymers. Near compositions of 50 vol %, our experiments agree with the fluctuation theories of both Fredrickson-Helfand and Muthukumar. At other compositions the critical for the ODT is smaller than that predicted by the available theories. This discrepancy increases as the copolymer composition deviates further from 50 vol %. In addition, transitions from one ordered morphology to another, order-order transitions, exhibit only a slight dependence on the composition.
Polymer, 2020
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Polymer, 2009
The solid-state morphology of polystyrene-poly(ethylene oxide) metallo-supramolecular diblock copolymer PS 20-[Ru]-PEO 70 , has been investigated by small-and wide-angle X-ray scattering and atomic force microscopy. Above the melting point of PEO the metal-ligand complexes and their associated counter ions are known to form aggregates within the still disordered polymer matrix of PS and PEO. Crystallization of PEO induces microphase separation between the PS and the PEO blocks. In addition, the metal-ligand aggregates are forced out of the crystalline PEO part and subsequently order at the interface in the amorphous PS block into a (short-range) square lattice.