High‐throughput characterization of pattern formation in symmetric diblock copolymer films

Abstract

Surface‐pattern formation in thin block copolymer films was investigated by utilizing a high‐throughput methodology to validate the combinatorial measurement approach and to demonstrate the value of the combinatorial method for scientific investigation. We constructed measurement libraries from images of subregions of block copolymer films having gradients in film thickness and a range of molecular mass, M. A single gradient film covers a wide range of film morphologies and contains information equivalent to a large number of measurements of films having a fixed thickness, h. Notably, the scale of the surface patterns is generally much larger than the molecular dimensions so that the interpretation of the patterns is more subtle than ordering in bulk block copolymer materials, and there is no predictive theory of this type of surface‐pattern formation. We observed a succession of surface patterns that repeat across the film with increasing h [extended smooth regions, regions containing circular islands, labyrinthine (“spinodal”) patterns, holes, and smooth regions again]. The extended smooth regions and the labyrinthine patterns appear to be novel features revealed by our combinatorial study, and these patterns occurred as bands of h that were quantized by integral multiples of the bulk lamellar period, Lo. The magnitude of the height gradient influenced the width of the bands, and the smooth regions occupied an increasing fraction of the film‐surface area with an increasing film gradient. The average size of the spinodal patterns, λ, was found to scale as λ ∼ L −2.5italico or λ ∼ M−1.65 and reached a limiting size at long annealing times. The hole and island features had a size comparable to λ, and their size likewise decreased with increasing M. The smooth regions were attributed to an increase in the surface‐chain density in the outer brushlike block copolymer layer with increasing h, and the scaling of λ with M was interpreted in terms of the increasing surface elasticity with M. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2141–2158, 2001

Integration of MALDI-TOFMS as high-throughput screening tool into the workflow of combinatorial polymer research

“…Examples of such tailor-made HTS techniques include, for instance the fast determination of molar mass and molar mass distribution by rapid gel permeation chromatography, 11 the wettability of polymer libraries, 12 or the morphology of polymer gradient libraries. 13,14 However, until recently no feasible technique was described for the high-throughput determination of molar masses, molar mass distributions as well as of end-groups of synthetic polymers by mass spectrometry. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry ͑MALDI-TOFMS͒ has advanced to the perhaps most powerful MS tool for the analysis of polymers 15 since its introduction in the 1980s.…”

Multiscale Dewetting of Low-Molecular-Weight Block Copolymer Ultrathin Films

“…Numerous studies [1 -5] have sought to elucidate the conditions that govern the kinetics of surface pattern formation, as well as the topological features of the accompanying island, hole or spinodal pattern. Recent efforts [6,7] in this vein have employed combinatorial methods to establish the roles of experimental factors such as copolymer molecular weight, film thickness and temperature on pattern formation. While most studies conducted to date have focused on ultrathin films composed of block copolymers in the intermediate-or strong-segregation regimes, Green and coworkers, [8,9] however, have examined the dewetting characteristics of copolymer films at temperatures above the order-disorder transition (ODT).…”

Combinatorial Mapping of Substrate Step Edge Effects on Diblock Copolymer Thin Film Morphology and Orientation

“…For very thin films we see only WL; with increasing thickness t, we observe either single or double layers of spheres over the WL, which we denote as WL þ 1S and WL þ 2S, respectively. As has been previously observed [11,12] films of ''incommensurate'' thickness, not corresponding to an integer number of sphere layers over WL, can spontaneously form a terrace structure, a mixed morphology of alternating regions of the two nearest commensurate thicknesses. (Regions of the less prevalent morphology are often roughly circular, hence ''islands'' for greater thicknesses and ''holes'' for smaller thicknesses.)…”