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.
Citations
More filters
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
References
More filters
TL;DR: In this paper, the linear dynamic viscoelastic properties of functionalized block copolymer/organoclay nanocomposites were investigated and the organoclay employed (Cloisite 30B, Southern Clay Products) is natural clay.
Abstract: Linear dynamic viscoelastic properties of functionalized block copolymer/organoclay nanocomposites were investigated. The organoclay employed (Cloisite 30B, Southern Clay Products) is natural clay ...
76 citations
TL;DR: For normal phase chromatography on aminoproply-bonded silicas, the adsorption of the polar modifier of various mixtures of hexane with n -alkanols, benzyl alcohol, acetone, dimethylformamide, nitromethane, chloroform and diisopropyl ether were measured.
70 citations
TL;DR: In this paper, non-equilibrium molecular dynamics (NEMD) simulations were employed to study films in nanometer confinements under shear and they found that nearly all the shear thinning takes place inside the solid-oligomer interface and that the adsorbed layers are more viscous than the middle part of the films.
Abstract: Non-Equilibrium Molecular Dynamics (NEMD) computer simulations were employed to study films in nanometer confinements under shear. Focusing on the response of the viscosity, we found that nearly all the shear thinning takes place inside the solid-oligomer interface and that the adsorbed layers are more viscous than the middle part of the films. Moreover, the shear thinning inside the interfacial area is determined by the wall affinity and is largely insensitive to changes of the film thickness and the molecular architecture. The rheological response of the whole film is the weighted average of these two regions -''viscous'' interfacial layer and bulk-like middle part- resulting in an absence of a universal response in the shear thinning regime, in agreement with recent SFA experiments of fluid lubricants.
65 citations
TL;DR: In this article, the effects of surface configuration (including surface type, surface pattern period, and surface separation) on the morphology of confined diblock copolymer thin films were studied.
Abstract: Thin films of symmetric diblock copolymers confined between two hard, flat and parallel surfaces have been investigated by means of Monte Carlo simulations on a simple cubic lattice. The upper surface is homogeneous, either neutral or preferential to one of the two blocks, and the lower surface is stripe-patterned, with all the stripes having the same width Ls/2 and alternatively preferring A and B blocks with the same strength of preference. We studied the effects of surface configuration (including surface type, surface pattern period, and surface separation) on the morphology of confined diblock copolymer thin films. Our results show that two conditions are essential for obtaining macroscopically ordered (over micrometers) perpendicular lamellae in the confined films (with film thickness no less than the bulk lamellar period L0): a stripe-patterned substrate with pattern period Ls comparable to L0, which directs the ordering of perpendicular lamellae over a macroscopic scale, and a neutral or weakly p...
62 citations
"Thermodynamic Free Energy Behavior ..." refers result in this paper
...[31] However, in systems in which the surface affinities of both blocks are comparable, lamellae perpendicular to the confining surfaces have been observed in agreement with similar conclusions arrived at through Monte Carlo simulations.[32] Intercalation of block copolymers into layered silicates presents a real situation of block copolymer confinement between flat parallel surfaces, and this situation has been looked at via selfconsistent field theory for a description of the interactions between silicate surfaces and the block copolymers....
[...]
TL;DR: In this article, the influence of a highly anisotropic layered silicate (organically modified montmorillonite) in directing the mesoscopic self-assembly of a block copolymer blend is studied as a model for the development and tailoring of templated inorganic-organic hybrid materials.
Abstract: The influence of a highly anisotropic layered silicate (organically modified montmorillonite) in directing the mesoscopic self-assembly of a block copolymer blend is studied as a model for the development and tailoring of templated inorganic–organic hybrid materials. The potential for nanometer thick layers to induce large-scale mesoscopic ordering of cylindrical and spherical microdomains in asymmetric block copolymers is studied using a combination of rheology, electron microscopy, and small angle neutron scattering. Spherical microdomains arranged on a bcc lattice are templated by the anisotropic layered silicate and the kinetics of their growth are dramatically accelerated by the presence of even 0.1 wt.% (0.04 vol.%) of the filler. However, for cylindrical microdomain ordering, the kinetics are essentially unaffected by the addition of layered silicates and the development of three-dimensional mesoscopic order is possibly even disrupted. These results suggest that for the development of three-dimensional well-ordered nanostructures, the surface defining the pattern has to be significantly larger than the leading dimension of the structure being templated.
61 citations