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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.

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Schematic structures of the thin film duringswelling and drying:(a) as-prepared film at t = 0 s, (b) swollen filmat t = 828 s, (c) swollen film at t = 1350 s, (d) subsequently dried film at t = 7200s.
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fig7: Schematic structures of the thin film duringswelling and drying:(a) as-prepared film at t = 0 s, (b) swollen filmat t = 828 s, (c) swollen film at t = 1350 s, (d) subsequently dried film at t = 7200s.

Mentions: In summary,we have investigated the structural evolution of apoly(styrene-b-butadiene) diblock copolymer thinfilm having initially a distribution of lamellar orientations duringannealing with EAC vapor. The behavior of both the parallel and theperpendicular lamellae in the thin film is investigated in detail,which gives us a clue to fully understand the reorganizational processesduring SVA. The structural evolution of the thin film can be describedby the sketch shown in Figure 7. For the as-preparedsample, the lamellar spacing depends on the orientation of the lamellae.Whereas the parallel lamellae have the smallest spacing, the perpendicularones have the largest one (Figure 7a). Duringswelling, the perpendicular lamellae swell less easily than the parallelones because of the constraining effect of the substrate. However,both reach the same lamellar spacing after a certain time of swelling(Figure 7b). The orientational distributionof the lamellae is changed during swelling, and a completely parallelorientation is obtained at the end of the swelling process (Figure 7c). For 0.87 < ϕP < 0.95,the lamellar spacing increases and reaches the bulk (equilibrium)value. Unexpectedly, EAC turns out to act as a nonselective solventfor P(S-b-B) diblock copolymer. It screens the unfavorableinteractions between the PS and PB blocks, resulting in a decreasein the lamellar spacing with increasing solvent concentration. For0.77 < ϕP < 0.83, we find a scaling exponent,β = −0.32, which is in agreement with the theoreticalprediction.43 Comparing with previous resultson a thin film featuring initially parallel lamellae and being swollenin toluene,29 we find that the increaseof Dlampar is different, whereas the subsequent decrease during thelater stage of the swelling follows the same behavior. After drying,a thin film with exclusively parallel lamellae is obtained; however,their spacing, 0.91Dlambulk, is larger than in the as-preparedfilm, 0.65Dlambulk (Figure 7d).


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)

Schematic structures of the thin film duringswelling and drying:(a) as-prepared film at t = 0 s, (b) swollen filmat t = 828 s, (c) swollen film at t = 1350 s, (d) subsequently dried film at t = 7200s.
© Copyright Policy
Related In: Results  -  Collection

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

fig7: Schematic structures of the thin film duringswelling and drying:(a) as-prepared film at t = 0 s, (b) swollen filmat t = 828 s, (c) swollen film at t = 1350 s, (d) subsequently dried film at t = 7200s.
Mentions: In summary,we have investigated the structural evolution of apoly(styrene-b-butadiene) diblock copolymer thinfilm having initially a distribution of lamellar orientations duringannealing with EAC vapor. The behavior of both the parallel and theperpendicular lamellae in the thin film is investigated in detail,which gives us a clue to fully understand the reorganizational processesduring SVA. The structural evolution of the thin film can be describedby the sketch shown in Figure 7. For the as-preparedsample, the lamellar spacing depends on the orientation of the lamellae.Whereas the parallel lamellae have the smallest spacing, the perpendicularones have the largest one (Figure 7a). Duringswelling, the perpendicular lamellae swell less easily than the parallelones because of the constraining effect of the substrate. However,both reach the same lamellar spacing after a certain time of swelling(Figure 7b). The orientational distributionof the lamellae is changed during swelling, and a completely parallelorientation is obtained at the end of the swelling process (Figure 7c). For 0.87 < ϕP < 0.95,the lamellar spacing increases and reaches the bulk (equilibrium)value. Unexpectedly, EAC turns out to act as a nonselective solventfor P(S-b-B) diblock copolymer. It screens the unfavorableinteractions between the PS and PB blocks, resulting in a decreasein the lamellar spacing with increasing solvent concentration. For0.77 < ϕP < 0.83, we find a scaling exponent,β = −0.32, which is in agreement with the theoreticalprediction.43 Comparing with previous resultson a thin film featuring initially parallel lamellae and being swollenin toluene,29 we find that the increaseof Dlampar is different, whereas the subsequent decrease during thelater stage of the swelling follows the same behavior. After drying,a thin film with exclusively parallel lamellae is obtained; however,their spacing, 0.91Dlambulk, is larger than in the as-preparedfilm, 0.65Dlambulk (Figure 7d).

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