Thermodynamic Free Energy Behavior of Diblock Copolymer Chains Confined Between Planar Surfaces Having End-Tethered Flexible Polymer Molecules
10 May 2012-Journal of Macromolecular Science, Part B (Taylor & Francis Group)-Vol. 51, Iss: 7, pp 1282-1302
TL;DR: In this article, a molecular model for the free energy of a confined system of diblock copolymer chains within a 2D slit with the interior surfaces having end-tethered chains is presented, based on a combined lattice and scaling theory approach.
Abstract: A molecular model for the free energy of a confined system of diblock copolymer chains within a 2D slit with the interior surfaces having end-tethered chains is presented, based on a combined lattice and scaling theory approach. The thermodynamics of a model system, based on a constrained minimization of free energy, is explored as a function of the intermolecular energy parameters for interaction between the segments of block copolymer chains, end-tethered chains, and the surfaces. The effects of chain length and the block length ratio are investigated over a wide range of values. The results obtained are qualitative in nature; however, the model can be implemented to real systems provided appropriate parameterization of the model parameters to real systems can be performed. The phase diagrams obtained here provide ways for designing thermodynamically stable systems within the physical parametric variable space.
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01 Mar 2000
TL;DR: In this paper, a simulation of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates, is presented.
Abstract: Polymer-layered silicate nanocomposites may be formed by annealing layered silicate particles with a polymer melt. Polymer molecules flow from a bulk melt into the galleries between silicate sheets, swelling the silicate structure. The use of an amphiphilic intercalant raises possibilities of forming novel structures and enhancing the intercalation kinetics relative to the case of homopolymer intercalants. We perform molecular dynamics simulations of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates. Intercalation kinetics are examined for a variety of polymer–surface and interblock interactions and for thermodynamic states in which the bulk polymer occupies either a lamellar or disordered phase. Comparison to previous simulations of homopolymer intercalation demonstrates that diblock copolymers may be used to intercalate a block that would not spontaneously intercalate as a homopolymer.
34 citations
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TL;DR: In this article, a simulation of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates, is presented.
Abstract: Polymer-layered silicate nanocomposites may be formed by annealing layered silicate particles with a polymer melt. Polymer molecules flow from a bulk melt into the galleries between silicate sheets, swelling the silicate structure. The use of an amphiphilic intercalant raises possibilities of forming novel structures and enhancing the intercalation kinetics relative to the case of homopolymer intercalants. We perform molecular dynamics simulations of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates. Intercalation kinetics are examined for a variety of polymer–surface and interblock interactions and for thermodynamic states in which the bulk polymer occupies either a lamellar or disordered phase. Comparison to previous simulations of homopolymer intercalation demonstrates that diblock copolymers may be used to intercalate a block that would not spontaneously intercalate as a homopolymer.
37 citations
TL;DR: In this article, the diblock copolymer was synthesized by anionic polymerization using high-vacuum techniques and was molecularly characterized by size exclusion chromatography.
37 citations
TL;DR: In this paper, a diblock copolymer can be effectively intercalated within the clay galleries and the balance of these interactions give rise to a case where one block of the copolymers is interalated and the other forms a spring that keeps the clay platelets apart, i.e., "hairy" plates.
Abstract: The morphology and thermal properties have been investigated in laponite/poly(ethylene oxide) (PEO) clay/homopolymer and laponite/poly(ethylene oxide-b-isoprene) (PEO−PI) clay/block copolymer nanocomposites using small- and wide-angle X-ray scattering, optical microscopy, transmission electron microscopy, and differential scanning calorimetry. In the laponite/PEO composite, PEO intercalation adjusts the layer spacing and increases the layer correlation length. In the laponite/PEO−PI nanocomposite, the enthalpic interactions between the unlike blocks favoring nanophase separation work in tandem with the entropic interactions favoring polymer/clay intercalation, giving rise to multiple levels of organization. We show that (i) a diblock copolymer can be effectively intercalated within the clay galleries and (ii) the balance of these interactions give rise to a case where one block of the copolymer is intercalated and the other forms a spring that keeps the clay platelets apart, i.e., “hairy” plates.
34 citations
01 Mar 2000
TL;DR: In this paper, a simulation of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates, is presented.
Abstract: Polymer-layered silicate nanocomposites may be formed by annealing layered silicate particles with a polymer melt. Polymer molecules flow from a bulk melt into the galleries between silicate sheets, swelling the silicate structure. The use of an amphiphilic intercalant raises possibilities of forming novel structures and enhancing the intercalation kinetics relative to the case of homopolymer intercalants. We perform molecular dynamics simulations of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates. Intercalation kinetics are examined for a variety of polymer–surface and interblock interactions and for thermodynamic states in which the bulk polymer occupies either a lamellar or disordered phase. Comparison to previous simulations of homopolymer intercalation demonstrates that diblock copolymers may be used to intercalate a block that would not spontaneously intercalate as a homopolymer.
34 citations
"Thermodynamic Free Energy Behavior ..." refers background in this paper
...[ 43 – 46 ] The molecular simulation approach has revealed interesting aspects of the behavior of diblock copolymers in the intercalated confined state between silicate layers....
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TL;DR: In this article, molecular dynamics simulations of the flow of macromolecules from a bulk melt into a slit of nanometer dimension with strongly attracting walls are presented, which is central to the formation of polymer-layered silicate nanocomposites by direct melt intercalation.
Abstract: We present molecular dynamics simulations of the flow of macromolecules from a bulk melt into a slit of nanometer dimension with strongly attracting walls. Such flow is central to the formation of polymer-layered silicate nanocomposites by direct melt intercalation. In this process, polymer molecules flow from a melt into the galleries between the sheets that compose a mica-type layered silicate. We present a systematic study of the effects of polymer molecular weight and polymer-surface interactions on the flow dynamics.
32 citations