Direct imaging and mesoscale modelling of phase transitions in a nanostructured fluid

Abstract

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.

Cylindrical phase of diblock copolymers confined in thin films. A real-space self-consistent field theory study

“…These structures, such as the perpendicular cylinders, parallel cylinders with integer number of layers, flat lamellae, and perforated lamellae, have also been observed in previous experiments and simulations [24][25][26][27][28][29][30][31][32][33][44][45][46][47][48][49]. However, the undulated lamellae and cylinders, as well as parallel cylinders with fractional number (non-integer) of layers are found for the first time in the present real-space SCFT calculation.…”

“…Under confinement, diblock copolymers with cylindrical phase in the bulk may not only change the orientation of the cylinders, but also alternate between different morphologies, provided suitable polymer-substrate interaction energy and film thickness. Recently, the phase behavior of cylinder-forming triblock copolymer under thin films conditions attracts much attention [44][45][46][47][48][49].…”

“…the systems with upper and lower substrates having different preference to the blocks or there being some decorated pattern on the substrates; (b) surface reconstruction [44,46,47,49], i.e. wetting layer and the nearest two molecular layers against substrates being carefully examined; (c) hybrid structures [46][47][48], i.e. under confinements, different structures occurring in different horizontal layers, in the same horizontal layer, or connected with each other.…”

Scanning Force Microscopy as Applied to Conformational Studies in Macromolecular Research

“…[240,241] They demonstrated peculiar 'reptational' movements of flexible chain macromolecules on mica in a humid environment. [240,241] Time evolution of dynamics of surface relief and phase transition in the structure of block copolymer films were studied upon exposure to vapours [242,243] and also with additionally applied electric field. [244,245] Is was shown that different vapours may destabilise and induce dewetting of thin [246,247] and ultrathin-i.e., with thicknesses smaller than the radius of gyration of the unperturbed molecule R g [248] -polymer films.…”

Enhancing Ordering Dynamics in Solvent-Annealed Block Copolymer Films by Lithographic Hard Mask Supports

“…One group of factors concerns the inherent thermodynamic features of the microphase separation. [18][19][20] Belonging to soft matter, block copolymers are characterized by low interfacial and surface energies, small differences in the free energy between different morphological states, 21 and relatively small incompatibility parameters between the blocks, which all lead to easy stabilization of meta-stable states and defects. [22][23] This makes the selfassembly of block copolymers in thin films extremely sensitive to external fields and to experimental uncertainties, such as tiny variations in the environmental temperature, 24 humidity, 25 solvent concentration [26][27][28] and quality, [29][30][31][32] surface energy at the substrate, [33][34] film preparation [35][36][37] and film thickness, 38 etc.…”