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Lamellar Diblock Copolymer Thin Films during Solvent Vapor Annealing Studied by GISAXS: Different Behavior of Parallel and Perpendicular Lamellae.

Zhang J, Posselt D, Smilgies DM, Perlich J, Kyriakos K, Jaksch S, Papadakis CM - Macromolecules (2014)

Bottom Line: During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly.The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process.During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed.

View Article: PubMed Central - PubMed

Affiliation: Physik-Department, Fachgebiet Physik weicher Materie, Technische Universität München , James-Franck-Str. 1, 85748 Garching, Germany.

ABSTRACT
The reorientation of lamellae and the dependence of the lamellar spacing, D lam, on polymer volume fraction, ϕP, D lam ∝ ϕP (-β), in diblock copolymer thin films during solvent vapor annealing (SVA) are examined by combining white light interferometry (WLI) and grazing-incidence small-angle X-ray scattering (GISAXS). A thin film of lamellae-forming poly(styrene-b-butadiene) prepared by spin-coating features lamellae of different orientations with the lamellar spacing depending on orientation. During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly. Quantitatively, the swelling process is composed of three regimes and the drying process of two regimes. The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process. The rearrangement is attributed to the increase of mobility of the polymer chains imparted by the solvent and to a decrease of total free energy of the thin film. In the third regime of swelling, the scaling exponent is found to be β = -0.32. During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed.

No MeSH data available.


Related in: MedlinePlus

qz profiles at thebeginning (4800 s, ϕP = 0.95, lower red curve) andat the end (7200 s, ϕP = 1.0, upper black curve)of the second regime of drying (V). The curves are shifted verticallyfor better visibility. M1, P1, M2, P2, M3, and P3 mark the DBSs.
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fig6: qz profiles at thebeginning (4800 s, ϕP = 0.95, lower red curve) andat the end (7200 s, ϕP = 1.0, upper black curve)of the second regime of drying (V). The curves are shifted verticallyfor better visibility. M1, P1, M2, P2, M3, and P3 mark the DBSs.

Mentions: During drying, tworegimes are distinguished (Figure 5b): (IV)slow deswelling following Dlampar ∝ ϕP–0.43±0.01 for 0.77< ϕP < 0.95 and (V) faster deswellingfollowing Dlampar ∝ ϕP–0.84±0.04 for 0.95 <ϕP < 1. The initial drying (IV) is slower thanexpected for affine deswelling; i.e., the lamellar spacing is higherthan that resulting from affine deswelling. As the solvent is removed,nonfavorable segmental interactions increase, and the block copolymersundergo a reorganization within the entire film to accommodate theincommensurability between the surface area and the changing lamellarspacing. This means that additional thicker lamellae are formed viarearrangement of the lamellae, which is possible because, at thisdegree of swelling, the Tg of the PS domainsis still below room temperature.44 Thebehavior is different from the one which shows an increase of domainspacing during the deswelling process observed by Gu et al.9 However, in both cases the lamellar thicknesstends to reach the bulk equilibrium value. The subsequent drying (V)is affine. The beginning of this regime is at the same ϕP (Figure 4, ϕP = 0.95)as the beginning of the second regime of swelling; i.e., in this regime, Tg of PS is now above room temperature, whichdrastically reduces the mobility of the PS blocks and leads to a differentdrying mechanism. Owing to the low Tg ofPB, further evaporation of the solvent is expected to give rise toasymmetric lamellae. This speculation is supported by the experimentaldata. Figure 6 shows the qz profiles at the beginning and at theend of the second drying regime (V). The second-order DBSs M2 andP2 appear after drying, indicating that asymmetric lamellae are formed.


Lamellar Diblock Copolymer Thin Films during Solvent Vapor Annealing Studied by GISAXS: Different Behavior of Parallel and Perpendicular Lamellae.

Zhang J, Posselt D, Smilgies DM, Perlich J, Kyriakos K, Jaksch S, Papadakis CM - Macromolecules (2014)

qz profiles at thebeginning (4800 s, ϕP = 0.95, lower red curve) andat the end (7200 s, ϕP = 1.0, upper black curve)of the second regime of drying (V). The curves are shifted verticallyfor better visibility. M1, P1, M2, P2, M3, and P3 mark the DBSs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150605&req=5

fig6: qz profiles at thebeginning (4800 s, ϕP = 0.95, lower red curve) andat the end (7200 s, ϕP = 1.0, upper black curve)of the second regime of drying (V). The curves are shifted verticallyfor better visibility. M1, P1, M2, P2, M3, and P3 mark the DBSs.
Mentions: During drying, tworegimes are distinguished (Figure 5b): (IV)slow deswelling following Dlampar ∝ ϕP–0.43±0.01 for 0.77< ϕP < 0.95 and (V) faster deswellingfollowing Dlampar ∝ ϕP–0.84±0.04 for 0.95 <ϕP < 1. The initial drying (IV) is slower thanexpected for affine deswelling; i.e., the lamellar spacing is higherthan that resulting from affine deswelling. As the solvent is removed,nonfavorable segmental interactions increase, and the block copolymersundergo a reorganization within the entire film to accommodate theincommensurability between the surface area and the changing lamellarspacing. This means that additional thicker lamellae are formed viarearrangement of the lamellae, which is possible because, at thisdegree of swelling, the Tg of the PS domainsis still below room temperature.44 Thebehavior is different from the one which shows an increase of domainspacing during the deswelling process observed by Gu et al.9 However, in both cases the lamellar thicknesstends to reach the bulk equilibrium value. The subsequent drying (V)is affine. The beginning of this regime is at the same ϕP (Figure 4, ϕP = 0.95)as the beginning of the second regime of swelling; i.e., in this regime, Tg of PS is now above room temperature, whichdrastically reduces the mobility of the PS blocks and leads to a differentdrying mechanism. Owing to the low Tg ofPB, further evaporation of the solvent is expected to give rise toasymmetric lamellae. This speculation is supported by the experimentaldata. Figure 6 shows the qz profiles at the beginning and at theend of the second drying regime (V). The second-order DBSs M2 andP2 appear after drying, indicating that asymmetric lamellae are formed.

Bottom Line: During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly.The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process.During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed.

View Article: PubMed Central - PubMed

Affiliation: Physik-Department, Fachgebiet Physik weicher Materie, Technische Universität München , James-Franck-Str. 1, 85748 Garching, Germany.

ABSTRACT
The reorientation of lamellae and the dependence of the lamellar spacing, D lam, on polymer volume fraction, ϕP, D lam ∝ ϕP (-β), in diblock copolymer thin films during solvent vapor annealing (SVA) are examined by combining white light interferometry (WLI) and grazing-incidence small-angle X-ray scattering (GISAXS). A thin film of lamellae-forming poly(styrene-b-butadiene) prepared by spin-coating features lamellae of different orientations with the lamellar spacing depending on orientation. During annealing with ethyl acetate (EAC) vapor, it is found that perpendicular lamellae behave differently from parallel ones, which is due to the fact that their initial lamellar thicknesses differ strongly. Quantitatively, the swelling process is composed of three regimes and the drying process of two regimes. The first two regimes of swelling are associated with a significant structural rearrangement of the lamellae; i.e., the lamellae first become thicker, and then perpendicular and randomly oriented lamellae vanish, which results in a purely parallel orientation at the end of the swelling process. The rearrangement is attributed to the increase of mobility of the polymer chains imparted by the solvent and to a decrease of total free energy of the thin film. In the third regime of swelling, the scaling exponent is found to be β = -0.32. During drying, the deswelling is nonaffine which may be a consequence of the increase of nonfavorable segmental interactions as the solvent is removed.

No MeSH data available.


Related in: MedlinePlus