We have experimentally determined a phase diagram for cylinder-forming polystyrene-block-polybutadien-block-polystyrene triblock copolymer in thin films. The phase behavior can be modeled in great detail by dynamic density functional theory. Deviations from the bulk structure, such as wetting layer, perforated lamella, and lamella, are identified as surface reconstructions. Their stability regions are determined by an interplay between surface fields and confinement effects.

The phase behavior of cylinder-forming ABA block copolymers in thin films is modeled in detail using dynamic density functional theory and compared with recent experiments on polystyrene-block-polybutadiene-block-polystyrene triblock copolymers. Deviations from the bulk structure, such as wetting layer, perforated lamella, and lamella, are identified as surface reconstructions. Their stability regions are determined by an interplay between surface fields and confinement effects. Our results give evidence for a general mechanism governing the phase behavior in thin films of modulated phases.

The influence of confinement on morphology formation in copolymer systems is an important area of interest in theoretical research. We apply dynamic density functional theory to investigate the effect of pores on the morphology formation in a symmetric diblock copolymer system. The pore is represented by a perfect cylindrical tube. Porous systems are important in biology and are gaining interest for applications in nanotechnology. We show that for the pore sizes under investigation two equilibrium morphologies are possible depending on the surface interaction: a perpendicular or slab morphology and a parallel or multiwall tube morphology. The latter is referred to in the article as dartboard morphology. In the dynamic pathway towards this morphology an intermediate metastable helical phase is found. An important observation is that, for a wide range of pore radii and variations of polymer chain length, no mixed parallel/perpendicular morphologies were found: All observed morphologies are insensitive to the pore diameter.

The kinetics of phase transitions is essential for understanding pattern formation in structured fluids. These fluids play a key role in the morphogenesis of biological cells, and they are very common in pharmaceutical products and plastic materials. Until now, it has not been possible to follow phase transitions in structured fluids experimentally in real time and with high spatial resolution. Previous work has relied on static images and indirect experimental evidence from spatially averaging scattering experiments. Simulating the processes with computer models is a further challenge because of the multiple time and length scales involved. Our movies based on in situ scanning force microscopy show the time sequence of the elementary steps of a phase transition in a fluid film of block copolymer from the cylinder to the perforated lamella phase. The movies validate a versatile simulation model that gives physical insight into the nature of the process. Our approach provides a means of improving the study and understanding of pattern formation processes in nanostructured fluids. We expect a significant impact on nanotechnology where block copolymers serve as self-organized templates for the synthesis of inorganic nanostructured materials.

We simulate the microphase separation dynamics of aqueous solutions of the triblock polymer surfactants (ethylene oxide)13(propylene oxide)30(ethylene oxide)13 and (propylene oxide)19(ethylene oxide)33(propylene oxide)19 by a dynamic variant of mean-field density functional theory for Gaussian chains. This is the first 3D mesoscale model for the dynamic behavior of specific complex polymer solutions. Different mesoscale structures (micellar, hexagonal, bicontinuous, and lamellar and dispersed coexisting phases) are formed depending on composition. The numerical results are in good agreement with experiment. The intermediate hexagonal and bicontinuous phases of (ethylene oxide)13(propylene oxide)30(ethylene oxide)13 solution retain a rich defect structure. Concentrated solution (60%) of (propylene oxide)19(ethylene oxide)33(propylene oxide)19 shows the onset of macrophase separation, with small water droplets dispersed throughout the system. We confirm the experimental observation that the lamellar phase formation does not depend on the block sequence. Quenched from homogeneous state, the kinetics of each system consists of a fast local aggregation stage and subsequent slow rearrangement by defect annihilation. We conclude that the simulation method is a valuable tool for description of 3D morphology formation in a wide variety of complex polymer liquids.

The electric field alignment of cylindrical microdomains in diblock copolymer thin films was studied using small-angle neutron scattering and transmission electron microscopy. The alignment process was followed with the block copolymer films in different initial states. Starting from a poorly ordered state, the cylindrical microdomain orientation was biased by the surface field that initially drove the cylindrical microdomains to be oriented parallel to the film surface. With further annealing, the cylinders were disrupted locally and formed ellipsoid-shaped microdomains that, with time, connected into cylindrical microdomains oriented in the field direction. Starting from an ordered state with cylinders parallel to the surface, the applied electric field enhanced fluctuations at the interfaces of the microdomains. The growth of the fluctuations continued until the cylindrical microdomains broke up into spherical microdomains, similar to that seen in the thermoreversible cylinder-to-sphere order−order transition. With time, the spherical microdomains deformed into ellipsoidal domains that reconnected into cylindrical microdomains oriented at ∼45° with respect to the applied field direction. Further annealing aligned the tilted cylinders along the applied field direction. This reorientation process was much slower than from the poorly ordered state. The details of the realignment process are supported by computer simulations based on dynamic self-consistent-field theory.

We study the effect of dissimilar interfaces on the phase behavior of cylinder forming block copolymers in thin films by means of dynamic density-functional theory. In this article, we show that dissimilarity of the interfaces induces hybrid structures. These structures appear when the surface fields at the two interfaces stabilize different surface structures and/or reconstructions. We propose a general classification of hybrid structures and give an unifying description of phase behavior of cylinder forming block copolymer films. Our results are consistent with experimental observations.

An electric field induced sphere-to-cylinder transition in thin films of asymmetric polystyrene-b-poly(methyl methacrylate) diblock copolymers was observed. In the absence of an applied electric field, thin films of the asymmetric diblock copolymer consisted of layers of spherical microdomains with poor in-plane long-range ordering. Under a ∼40V/μm applied electric field, hexagonally packed cylindrical microdomains normal to the surface were found. Cross-sectional transmission electron microscopy images of the intermediate stages of the alignment indicated that, under an electric field, the asymmetric diblock copolymer formed spherical microdomains that were deformed into ellipsoids and, with time, interconnected into cylindrical microdomains oriented in the direction of the applied electric field. Simulations suggest that improved long-range order of the cylindrical microdomains could be achieved by cycling the electrical field.