Alignment of lamellar block copolymer microstructure in an electric field. 1. Alignment kinetics

Amundson, Karl; Helfand, Eugene; Quan, Xina; Smith, Steven D.

doi:10.1021/ma00063a010

Cited by 221 publications

(226 citation statements)

References 12 publications

(21 reference statements)

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“…38 The influence of the slit is at least twofold. First, it is known that external forces, like electric fields 48 and flow fields, 37 can reduce the time scales connected with long range ordering enormously. The influence of a slit on the ordering process can be thought of in terms of an external force.…”

Section: E Dynamics In a Slitmentioning

confidence: 99%

Asymmetric block copolymers confined in a thin film

Huinink

Brokken-Zijp

Dijk

et al. 2000

The Journal of Chemical Physics

186

318

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We have used a dynamic density functional theory ͑DDFT͒ for polymeric systems, to simulate the formation of micro phases in a melt of an asymmetric block copolymer, A n B m ( f A ϭ1/3), both in the bulk and in a thin film. In the DDFT model a polymer is represented as a chain of springs and beads. A spring mimics the stretching behavior of a chain fragment and the spring constant is calculated with the Gaussian chain approximation. Simulations were always started from a homogeneous system. We have mainly investigated the final morphology, adopted by the system. First, we have studied the bulk behavior. The diblock copolymer forms a hexagonal packed array of A-rich cylinders, embedded in a B-rich matrix. Film calculations have been done by confining a polymer melt in a slit. Both the slit width and surface-polymer interactions were varied. With the outcomes a phase diagram for confined films has been constructed. Various phases are predicted: parallel cylinders (C ʈ ), perpendicular cylinders (C Ќ ), parallel lamellae (L ʈ ), and parallel perforated lamellae (CL ʈ ). When the film surfaces are preferentially wet by either the A or the B block, parallel oriented microdomains are preferred. A perpendicular cylindrical phase is stable when neither the A nor B block preferentially wets the surfaces. The predicted phase diagram is in accordance with experimental data in the literature and explains the experimentally observed differences between films of asymmetric block copolymers with only two parameters: the film thickness and the energetic preference of the surface for one of the polymer blocks. We have also observed, that confinement speeds up the process of long range ordering of the microdomains.

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Section: E Dynamics In a Slitmentioning

confidence: 99%

Asymmetric block copolymers confined in a thin film

Huinink

Brokken-Zijp

Dijk

et al. 2000

The Journal of Chemical Physics

186

318

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“…Ultimately, dielectric breakdown limits the applicability of electric fields to alter block copolymeric patterns. [16][17][18] Magnetic fields should in principle also lead to spatial reorientations of copolymer blocks. They are attractive as no limitations to the field strength and sample configuration exist.…”

mentioning

confidence: 99%

Self-organized two-dimensional onions

Ren

Briber

Wuttig

2009

Applied Physics Letters

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Spontaneously self-assembled onion-type nanostructures based on block copolymers as templating materials are reported. Polystyrene-poly͑ethylene oxide͒ diblock copolymer containing CoFe 2 O 4 and Pb 1.1 ͑Zr 0.53 Ti 0.47 ͒O 3 precursors segregated to the two microdomains forms well-ordered templated lamellar structures. Onion-type nanostructures have been induced by room temperature solvent annealing for 64 h in a magnetic field of 0.8 T oriented perpendicularly to the plane of film. The recorded images suggest that the Lorentz force acting on charges in the paraelectric precursor induces a circular component of the diffusion flux that leads to the onion formation. This templating process opens a route for nanometer-scale patterning of magnetic toroids. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3101373͔ Block copolymers have attracted much attention as prominent systems for nanotechnological applications because of their ability to spontaneously develop patterns on a nanoscale based on self-assembly. [1][2][3][4] Currently, a great deal of attention is being paid to the synthesis of complex nanostructured inorganic-organic hybrid materials. 5-10 A typical approach is the use of organic structures formed through self-assembly as structure directing agents. The final morphology is then determined by the cooperative organization of inorganic and organic molecular species into threedimensionally structured arrays. 11 In thin films, in addition to composition and molecular weight, the domain structure is also dependent on the surface energies of the blocks and on geometrical constraints introduced by the film. A recent example of inorganic-organic hybrid templating is the fabrication of ultrahigh density ferromagnetic nanocylinders that are embedded in a piezoelectric matrix by utilizing a precursorcontaining polystyrene-block-polyethylene oxide block copolymer. 12 The morphology and orientations of microdomains are the key factors controlling the properties of the patterned materials. The limited control over order and orientation of the microdomain in thin films poses restrictions on possible usages of patterning innovative material configurations via block copolymers. 13 Recent work demonstrates the alignment of block copolymers by electromagnetic fields. 14,15 Electric field induced alignment has been shown to be especially useful in thin film systems in which the two blocks have different dielectric constants. It does, however, require special sample geometries and surface preparation in the form of electrodes and patterned surfaces. Ultimately, dielectric breakdown limits the applicability of electric fields to alter block copolymeric patterns. [16][17][18] Magnetic fields should in principle also lead to spatial reorientations of copolymer blocks. They are attractive as no limitations to the field strength and sample configuration exist. Magnetic field induced alignment was reported in 1998; 19 a 2.4 T magnetic field was imposed on a diblock copolymer comprising both block chains of liquidcrystallin...

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“…According to [3] we adopt the expansion of the dielectric constant in powers of the order parameter up to quadratic terms…”

Section: B Contribution Of the Electric Field To The Effective Hamilmentioning

confidence: 99%

Fluctuation Effects in the Theory of Microphase Separation of Diblock Copolymers in the Presence of an Electric Field

et al. 2007

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We generalize the Fredrickson-Helfand theory of the microphase separation in symmetric diblock copolymer melts by taking into account the influence of a time-independent homogeneous electric field on the composition fluctuations within the self-consistent Hartree approximation. We predict that electric fields suppress composition fluctuations, and consequently weaken the first-order transition. In the presence of an electric field the critical temperature of the order-disorder transition is shifted towards its mean-field value. The collective structure factor in the disordered phase becomes anisotropic in the presence of the electric field. Fluctuational modulations of the order parameter along the field direction are strongest suppressed. The latter is in accordance with the parallel orientation of the lamellae in the ordered state.

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Alignment of lamellar block copolymer microstructure in an electric field. 1. Alignment kinetics

Cited by 221 publications

References 12 publications

Asymmetric block copolymers confined in a thin film

Asymmetric block copolymers confined in a thin film

Self-organized two-dimensional onions

Fluctuation Effects in the Theory of Microphase Separation of Diblock Copolymers in the Presence of an Electric Field

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