Morphological Evolution of Gyroid-Forming Block Copolymer Thin Films with Varying Solvent Evaporation Rate

Block copolymers can assume a range of microphase-separated morphologies, and the dependence of morphology on temperature and composition is an area of active research. Our work has been studying the morphology of solvent-cast thin films of polystyrene-polybutadiene-polystyrene (SBS) as a function of solvent evaporation rate and post-specimen annealing. This paper describes the analysis of thin film cross-sections to distinguish between possible morphologies. ∼50 nm-0.5 μm thick films were cast from a 0.1 wt% solution of SBS (30 wt%, Mw=105) in toluene. GPC analysis indicates PS/PB diblock and PS homopolymer is present (<5wt% total). 50 μl of solution was deposited on water-polished salt. The solvent evaporation rate was roughly controlled between 200 nl/sec and 0.2 nl/sec. After evaporation, the film was cut, floated from the salt, collected on grids, and exposed to OsO4 vapor (20 min) to stain the PB. After plan view study, some specimens were cross-sectioned. A carbon layer was evaporated on both sides prior to embedding in epoxy and ultramicrotomy(−130°C). Microscopy used a Philips CM3 0ST TEM.

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Cylinder Orientation Mechanism in Block Copolymer Thin Films Upon Solvent Evaporation

Macromolecules ◽

10.1021/ma1012946 ◽

2010 ◽

Vol 43 (18) ◽

pp. 7763-7770 ◽

Cited By ~ 159

Author(s):

William A. Phillip ◽

Marc A. Hillmyer ◽

E. L. Cussler

Keyword(s):

Thin Films ◽

Block Copolymer ◽

Solvent Evaporation ◽

Orientation Mechanism

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Morphological transformations in solution-cast Styrene-Butadiene-Styrene (SBS) triblock copolymer thin films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013729x ◽

1995 ◽

Vol 53 ◽

pp. 184-185

Author(s):

Ginam Kim ◽

W. Marsillo ◽

M. Libera

Keyword(s):

Thin Films ◽

Triblock Copolymer ◽

Annealing Treatment ◽

Minor Component ◽

Solvent Evaporation ◽

Single Crystal Substrate ◽

Transparent Films ◽

Crystal Substrate ◽

Solution Cast ◽

Morphological Transformations

The fact that block copolymers can assume a range of morphologies depending upon such variables as relative block length and molecular weight is now well known. In the case of poly(styrene)[PS]-poly(butadiene)[PB]-poly(styrene) (SBS) triblock copolymer, the morphologies range from spheres (roughly ~20% minor component), to cylinders (roughly 20%~35% minor component), to lamellae (roughly equal component fractions) Most recently, there has been increasing interest in transformations between morphologies by thermal annealing. This paper describes initial results studying the effect of solvent evaporation rate and post-casting annealing treatment on the morphology of SBS thin films.TEM specimens were prepared by solution casting electron transparent films. 50 μl of 0.1 wt% SBS (30% styrene, Mw=14,000, Scientific Polymer Products, Inc.) dissolved in toluene was deposited on a polished NaCl single crystal substrate placed in a small dish. After solvent evaporation the film was cut into small squares, floated from the salt in water, and each square was collected on a Cu grid.

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