Effect of Confinement on the Mesoscale and Macroscopic Swelling of Thin Block Copolymer Films

Abstract

We report on the swelling behavior and the corresponding morphological behavior of cylinder-forming polystyrene-b-polybutadiene diblock copolymers, which are confined to several layers of structures. The equilibration of thin films has been done under controlled atmosphere of a nonselective solvent. In situ spectroscopic ellipsometry measurements revealed more than 10% increase of the solvent uptake with decreasing film thickness. With scanning force microscopy of the microphase separated patterns in quenched films, the correlation between the degree of the long-range order of cylinder domains and the degree of the macroscopic swelling has been established. In the case of spontaneously formed micrometer-sized topographic features with discreet film thickness (terraces), the increased solvent uptake by thinner films holds true even for isolated terraces on the mesoscale. The observation of nonhomogeneous swelling of the films on the micrometer scale brings novel insights into the properties of confined soft matter, and suggests new approaches toward the fabrication of polymer-based nanostructured responsive materials.

Dewetting behavior of Langmuir−Blodgett films of polystyrene‐b‐poly(methyl methacrylate) induced by solvent vapor annealing

“…It is well known that block copolymers (BCPs) can self‐assemble into nanometer‐sized domains due to thermodynamic instability . One important method by which such self‐assembly structures can be further adjusted is solvent vapor annealing (SVA) . Once a BCP film is exposed to solvent vapor, polymer chains will absorb solvent molecules and the Flory–Huggins interaction parameter between polymer blocks or polymer blocks and the substrate will be significantly reduced, which results in the improvement of their mobility and lowering of the barrier to rearrangement of BCP .…”

“…[1][2][3][4][5][6] One important method by which such self-assembly structures can be further adjusted is solvent vapor annealing (SVA). [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Once a BCP film is exposed to solvent vapor, polymer chains will absorb solvent molecules and the Flory-Huggins interaction parameter between polymer blocks or polymer blocks and the substrate will be significantly reduced, which results in the improvement of their mobility and lowering of the barrier to rearrangement of BCP. 14,15 Gu and colleagues investigated the effect of processing history on the morphology evolution in polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films, and they indicated that the rearrangement of BCP microdomains towards equilibrium structure took place above a threshold swelling ratio.…”

“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Once a BCP film is exposed to solvent vapor, polymer chains will absorb solvent molecules and the Flory-Huggins interaction parameter between polymer blocks or polymer blocks and the substrate will be significantly reduced, which results in the improvement of their mobility and lowering of the barrier to rearrangement of BCP. 14,15 Gu and colleagues investigated the effect of processing history on the morphology evolution in polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films, and they indicated that the rearrangement of BCP microdomains towards equilibrium structure took place above a threshold swelling ratio. 16 Li et al found that the swelling degree and mobility of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) chains were influenced by solvent vapor pressure and preferential affinity of acetone vapor for PMMA blocks.…”

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

“…21 Analysis of the phase behavior under controlled solvent vapor treatment allowed to gain important insights into the mechanisms of microphase separation of conjugated polymers, 5 and of microdomain reorientation and ordering under combined application of solvent annealing and of electric field. [55][56][57][58] Furthermore, confinement effects on the microphase separation and swelling of thin 24,59 and thick 55,37 block copolymer films have become evident in the thickness-dependent swelling as well as in heterogeneous swelling of block copolymer films. 24,60,61 In the last years similar climate-controlled solvent-vapor annealing devices have been adopted and successfully exploited by several research groups.…”

Solvent‐Vapor‐Induced Rapid Assembly of Block‐Copolymer Film via Prevacuumizing

“…In such a case, solvent annealing provides an attractive alternative to thermal annealing. Since sufficient mobility of the copolymer chains is easily induced by solvent annealing at room temperature without the danger of degradation only with the film thickness changing, the way of solvent annealing has been used more and more widely . However, in most conventional BCP assembly processes undergone solvent annealing, a prolonged annealing approach is reported .…”