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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

(a) Selected 2D GISAXS images during swelling with EAC vapor. Thetimes after the beginning of the SVA are indicated. The exposure timeis 5 s for the images taken at 1385 and 1474 s, else 30 s. The intensityscale is given below the images. The M1, P1, M3, and P3 peaks aremarked as well as the Yoneda band; see text. The red arcs are thecalculated DDSRs; see text. (b) qz profile measured at 0 s (black line) and model curve calculatedusing the symmetric model (red line); see text. (c) qz profile measured at 966 s (black line)and model curves calculated using the symmetric model (red line) andthe asymmetric model (blue line). For the latter, an asymmetry of0.55 was chosen, just high enough to reveal the position of the M2and P2 reflections.
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fig2: (a) Selected 2D GISAXS images during swelling with EAC vapor. Thetimes after the beginning of the SVA are indicated. The exposure timeis 5 s for the images taken at 1385 and 1474 s, else 30 s. The intensityscale is given below the images. The M1, P1, M3, and P3 peaks aremarked as well as the Yoneda band; see text. The red arcs are thecalculated DDSRs; see text. (b) qz profile measured at 0 s (black line) and model curve calculatedusing the symmetric model (red line); see text. (c) qz profile measured at 966 s (black line)and model curves calculated using the symmetric model (red line) andthe asymmetric model (blue line). For the latter, an asymmetry of0.55 was chosen, just high enough to reveal the position of the M2and P2 reflections.

Mentions: Figure 2a shows selected 2D GISAXS imagesobtained during SVA. The GISAXS image of the as-prepared film (Figure 2a, image taken at 0 s) shows a pair of first-orderDDSRs, their intensities being enhanced between the Yoneda peaks ofP(S-b-B) and SiOx, inthe so-called Yoneda band.41 In addition,the intensities of the DDSRs are significantly enhanced near qy = 0; i.e., a significantfraction of the lamellae is parallel to the film surface. Thus, thethin film features mainly parallel lamellae with a small portion ofrandomly oriented ones.26,30 We note that this inhomogeneousintensity distribution indicates that the film is not disordered.30 This is in line with the fact that the χN value of the P(S-b-B) diblock copolymerunder study is as high as 26, i.e., far higher than the value at theorder-to-disorder transition (∼10.5). To characterize the innerstructure quantitatively, the first-order DDSRs were fitted by eq 2 in the following way: First, to determine the spacingof the parallel lamellae, a qz profile was created from the experimental 2D GISAXS imageby averaging over a narrow qy range (−0.002 Å–1 < qy < 0.002 Å–1) along qz (Figure 2b). Second, the lamellar spacing was determinedfrom this qz profileby using the software and model described in the Experimental Section and varying the spacing of the parallellamellae and αi to match the qz peak positions of the first-orderBragg reflections M1 and P1. While the calculated curve cannot reproducethe width of the peaks, the peak positions of M1 and P1 are well reproduced(Figure 2b). The best match was obtained for Dlampar = 145.5 ± 1 Å and αi = 0.178 ± 0.001°. The film thickness of 3260 ± 10Å thus amounts to 22.4Dlampar. The value of αi is very close to the nominal value of 0.18°,which confirms that the sample adjustment is reliable; however, Dlampar is significantly smaller than the bulk value. Third, using this Dlampar value, the calculated DDSRs were derived from eq 2. It is found that neither the calculated M1 nor the calculatedP1 DDSRs fit the measured ones, which indicates that the lamellarspacing depends on the orientation of the lamellae, whereas the parallellamellar spacing is much smaller than the perpendicular. Using Bragg’slaw, we find Dlamperp = 230 ± 1 Å, which is close tothe value of bulk sample. Shear forces during the film preparationby spin-coating may be at the origin of the orientation dependenceof the lamellar spacing. We anticipate that such kind of inner structuremay give rise to different behaviors for parallel and perpendicularlamellae during SVA.


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)

(a) Selected 2D GISAXS images during swelling with EAC vapor. Thetimes after the beginning of the SVA are indicated. The exposure timeis 5 s for the images taken at 1385 and 1474 s, else 30 s. The intensityscale is given below the images. The M1, P1, M3, and P3 peaks aremarked as well as the Yoneda band; see text. The red arcs are thecalculated DDSRs; see text. (b) qz profile measured at 0 s (black line) and model curve calculatedusing the symmetric model (red line); see text. (c) qz profile measured at 966 s (black line)and model curves calculated using the symmetric model (red line) andthe asymmetric model (blue line). For the latter, an asymmetry of0.55 was chosen, just high enough to reveal the position of the M2and P2 reflections.
© Copyright Policy
Related In: Results  -  Collection

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

fig2: (a) Selected 2D GISAXS images during swelling with EAC vapor. Thetimes after the beginning of the SVA are indicated. The exposure timeis 5 s for the images taken at 1385 and 1474 s, else 30 s. The intensityscale is given below the images. The M1, P1, M3, and P3 peaks aremarked as well as the Yoneda band; see text. The red arcs are thecalculated DDSRs; see text. (b) qz profile measured at 0 s (black line) and model curve calculatedusing the symmetric model (red line); see text. (c) qz profile measured at 966 s (black line)and model curves calculated using the symmetric model (red line) andthe asymmetric model (blue line). For the latter, an asymmetry of0.55 was chosen, just high enough to reveal the position of the M2and P2 reflections.
Mentions: Figure 2a shows selected 2D GISAXS imagesobtained during SVA. The GISAXS image of the as-prepared film (Figure 2a, image taken at 0 s) shows a pair of first-orderDDSRs, their intensities being enhanced between the Yoneda peaks ofP(S-b-B) and SiOx, inthe so-called Yoneda band.41 In addition,the intensities of the DDSRs are significantly enhanced near qy = 0; i.e., a significantfraction of the lamellae is parallel to the film surface. Thus, thethin film features mainly parallel lamellae with a small portion ofrandomly oriented ones.26,30 We note that this inhomogeneousintensity distribution indicates that the film is not disordered.30 This is in line with the fact that the χN value of the P(S-b-B) diblock copolymerunder study is as high as 26, i.e., far higher than the value at theorder-to-disorder transition (∼10.5). To characterize the innerstructure quantitatively, the first-order DDSRs were fitted by eq 2 in the following way: First, to determine the spacingof the parallel lamellae, a qz profile was created from the experimental 2D GISAXS imageby averaging over a narrow qy range (−0.002 Å–1 < qy < 0.002 Å–1) along qz (Figure 2b). Second, the lamellar spacing was determinedfrom this qz profileby using the software and model described in the Experimental Section and varying the spacing of the parallellamellae and αi to match the qz peak positions of the first-orderBragg reflections M1 and P1. While the calculated curve cannot reproducethe width of the peaks, the peak positions of M1 and P1 are well reproduced(Figure 2b). The best match was obtained for Dlampar = 145.5 ± 1 Å and αi = 0.178 ± 0.001°. The film thickness of 3260 ± 10Å thus amounts to 22.4Dlampar. The value of αi is very close to the nominal value of 0.18°,which confirms that the sample adjustment is reliable; however, Dlampar is significantly smaller than the bulk value. Third, using this Dlampar value, the calculated DDSRs were derived from eq 2. It is found that neither the calculated M1 nor the calculatedP1 DDSRs fit the measured ones, which indicates that the lamellarspacing depends on the orientation of the lamellae, whereas the parallellamellar spacing is much smaller than the perpendicular. Using Bragg’slaw, we find Dlamperp = 230 ± 1 Å, which is close tothe value of bulk sample. Shear forces during the film preparationby spin-coating may be at the origin of the orientation dependenceof the lamellar spacing. We anticipate that such kind of inner structuremay give rise to different behaviors for parallel and perpendicularlamellae during SVA.

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