Morphology Evolution of Thin Polystyrene Film During the Non-solvent Driven Dewetting Process†

doi:10.7503/cjcu20150553

Abstract

Abstract:

We investigated the dewetting process of thin polystyrene(PS) film induced by different non-solvents via atomic force microscope(AFM). It is found that the non-solvent induced dewetting of thin PS film is via the penetration-replacement mechanism. The morphology of thin PS film depends on the relative velocity of the hole forming process and the hole growth process. When the thickness of PS film is 15 nm, with the increase of the alkyl chain of solvents, the number of holes significantly decreased, while the size of the holes obviously increased. When the thickness of PS film increased to 25 nm, with the increase of the alkyl chain of solvents, the formation of the number of holes is slightly low and the film morphology is a long-range ordered double continuous structure. When the PS film thickness is 35 nm, the number of holes decreased significantly comparing with the other two films. In addition, temperature and molecular weight can further reduce the number of holes in the process of dewetting and form fractal morphology.

Key words: Thin polymer film, Dewetting mechanism, Non-solvent induced dewetting, Surface morphology

CLC Number:

O631

TrendMD:

XU Lin, ZHANG Huanhuan, SHI Tongfei. Morphology Evolution of Thin Polystyrene Film During the Non-solvent Driven Dewetting Process^†[J]. Chem. J. Chinese Universities, 2016, 37(1): 174.

Figures/Tables 5

Scheme 1 Schematic of experimental apparatus

Fig.1 AFM height images of thin PS film(Mw=2500, h=15 nm) as a function of exposure time(ta) to methyl alcohol vapor at 35 ℃^ta/s: (A) 15; (B) 30; (C) 60; (D) 140.

Fig.2 AFM height images of thin PS film(Mw=2500) as a function of exposure time during the dewetting process induced by different solvents at 35 ℃^(A) h=15 nm, methyl alcohol, ta=60 s; (B) h=15 nm, ethyl alcohol, ta=60 s; (C) h=15 nm, n-butyl alcohol, ta=30 s; (D) h=26 nm, methyl alcohol, ta=7 min; (E) h=26 nm, ethyl alcohol, ta=5 min; (F) h=26 nm, n-butyl alcohol, ta=2.5 min; (G) h=34 nm, methyl alcohol, ta=50 min; (H) h=34 nm, ethyl alcohol, ta=20 min; (I) h=34 nm, n-butyl alcohol, ta=5 min.Inset: 2D FFT images.

Fig.3 AFM height images of PS film(Mw=2500, h=15 nm) as a function of exposure time during the dewetting process induced by different solvents at 15 ℃^ (A) Methyl alcohol, ta=60 h; (B) ethyl alcohol, ta=150 min; (C) n-butyl alcohol, ta=30 min.

Fig.4 AFM height images of PS film(Mw=5400, h=26 nm) with different exposure time during the dewetting process induced by different solvent at 35 ℃^ (A) Methyl alcohol, ta=60 h; (B) ethyl alcohol, ta=16 h; (C) n-butyl alcohol, ta=12 h.

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