Composition fluctuations before dewetting in polystyrene/poly(vinyl methyl ether) blend thin films

Abstract

a b s t r a c tWe report structural development in blend thin films of deuterated polystyrene (dPS) and poly(vinyl methyl ether) (PVME) below w200 nm in two phase region during the incubation period before dewetting using neutron reflectivity (NR) and atomic force microscopy (AFM). As was predicted by the former optical microscope (OM) and small-angle light scattering (LS) measurements on blend thin films of protonated PS and PVME [Ogawa H, Kanaya T, Nishida K, Matsuba G. Polymer 2008;40:254-62.], the NR results clearly showed that the tri-layer structure consisting of the surface PVME layer, the middle blend layer and the bottom PVME layer was formed in the one phase region. After the temperature jump into the two phase region, it was found that the phase separation of the middle blend layer proceeded in the depth direction during the incubation period before dewetting, suggesting that the dewetting was induced by the composition fluctuations during the incubation period.

Time-resolved specular and off-specular neutron reflectivity measurements on deuterated polystyrene and poly(vinyl methyl ether) blend thin films during dewetting process

“…As shown in a previous paper 23 the specular reflectivity profile could be described by a trilayer model consisting of surface PVME layer at air, middle blend layer, and interface PVME layer at Si substrate even in the one phase region because preferential interactions are considered between PVME and air [30][31][32][33][34] and between PVME and Si substrate. 19,20 In the trilayer model the surface roughness and the interface roughness were introduced by an error function.…”

“…The dewetting of the phase separated polymer blend thin film limits the industrial applications because they require stable, homogeneous, and uniform thin films. This motivated the fundamental studies of polymer blend thin films very much to reveal the dewetting mechanism and control the morphology 4 for blend thin films of poly͑p-methylstyrene͒ ͑PpMS͒ and deuterated PS ͑dPS͒, 12 poly ͑styrene-ran-acrylonitrile͒ and deuterated poly ͑methyl methacrylate͒, [13][14][15][16][17] and PS and poly ͑vinyl methyl ether͒ ͑PVME͒ [18][19][20][21][22][23] in various film thickness ranges.…”

“…In order to see what structure formation occurs in the incubation period we performed neutron reflectivity measurements on blend thin films of dPS and PVME. 23 The measurements were done by quenching the samples after annealing in two phase region for a give period. We found that the phase separation in the depth direction occurred during the incubation period before dewetting.…”

“…15,16 In this work, we performed time-resolved specular and off-specular neutron reflectivity measurements on the dewetting process of dPS/PVME blend thin films 42 and 98 nm thick in two phase region using a time-of-flight ͑or energy dispersive͒ neutron reflectometer to study the details of phase separation in the depth direction before dewetting observed in the previous measurements. 23 In addition, we analyzed, for the first time, the off-specular data to demonstrate that the time-of-flight reflectivity measurements are very powerful to investigate kinetics of structure formation in the film plane in micrometer scale.…”

Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

“…In recent years, experimental work has been devoted to studying the phase-separation mechanism in polymer solutions, [1][2][3][4] polymer blends [5][6][7][8][9][10][11][12] and colloid-polymer mixtures [13][14][15][16][17] using small-angle light scattering (SALS). The aim of these studies was to control the morphology of the fabricated material and thus directly change the structure and properties of the product.…”