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Title: Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene

Abstract

A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, M{sub N}{sup PEO}=8.8 kg/mol, and a number average molecular weight of PS blocks, M{sub N}{sup PS}=24.5 kg/mol, (volume fraction of the PEO blocks, f{sub PEO}, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3 nm, and the hexagonal lattice was a=25.1 nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer (M{sub N}{sup PEO}=8.7 kg/mol and M{sub N}{sup PS}=9.2 kg/mol) and a PS homo-polymer (M{sub N}{sup PS}=4.6 kg/mol) in which the f{sub PEO} was 0.32. The cylinder diameter in this blend sample was 13.7 nm and the hexagonal lattice was a=23.1 nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the M{sub N}{sup PS} of PS homo-polymer is lower than themore » PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect-controlled process. The mean crystallite sizes were estimated by the Scherer equation, and the PEO crystal sizes are on the scale of the confined size.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914329
Report Number(s):
BNL-78897-2007-JA
Journal ID: ISSN 0032-3861; POLMAG; TRN: US200809%%26
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Polymer; Journal Volume: 47; Journal Issue: 15
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CONFINEMENT; COPOLYMERS; CRYSTALLIZATION; HEXAGONAL LATTICES; MOLECULAR WEIGHT; POLYSTYRENE; POLYETHYLENE GLYCOLS; CYLINDRICAL CONFIGURATION; PHASE STUDIES; national synchrotron light source

Citation Formats

Huang,P., Guo, Y., Quirk, R., Ruan, J., Lotz, B., Thomas, E., Hsiao, B., Avila-Orta, C., Sics, I., and Cheng, S.. Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene. United States: N. p., 2006. Web. doi:10.1016/j.polymer.2005.06.129.
Huang,P., Guo, Y., Quirk, R., Ruan, J., Lotz, B., Thomas, E., Hsiao, B., Avila-Orta, C., Sics, I., & Cheng, S.. Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene. United States. doi:10.1016/j.polymer.2005.06.129.
Huang,P., Guo, Y., Quirk, R., Ruan, J., Lotz, B., Thomas, E., Hsiao, B., Avila-Orta, C., Sics, I., and Cheng, S.. Sun . "Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene". United States. doi:10.1016/j.polymer.2005.06.129.
@article{osti_914329,
title = {Confined Cylinders Constructed by a Poly(ethylene oxide)-b-polystyrene Diblock Copolymer and a Blend of Poly(ethylene Oxide)-b-Polystyrene and Polystyrene},
author = {Huang,P. and Guo, Y. and Quirk, R. and Ruan, J. and Lotz, B. and Thomas, E. and Hsiao, B. and Avila-Orta, C. and Sics, I. and Cheng, S.},
abstractNote = {A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, M{sub N}{sup PEO}=8.8 kg/mol, and a number average molecular weight of PS blocks, M{sub N}{sup PS}=24.5 kg/mol, (volume fraction of the PEO blocks, f{sub PEO}, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3 nm, and the hexagonal lattice was a=25.1 nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer (M{sub N}{sup PEO}=8.7 kg/mol and M{sub N}{sup PS}=9.2 kg/mol) and a PS homo-polymer (M{sub N}{sup PS}=4.6 kg/mol) in which the f{sub PEO} was 0.32. The cylinder diameter in this blend sample was 13.7 nm and the hexagonal lattice was a=23.1 nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the M{sub N}{sup PS} of PS homo-polymer is lower than the PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect-controlled process. The mean crystallite sizes were estimated by the Scherer equation, and the PEO crystal sizes are on the scale of the confined size.},
doi = {10.1016/j.polymer.2005.06.129},
journal = {Polymer},
number = 15,
volume = 47,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • A poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer with number-average molecular weights of 7.7k g/mol for the PS block and 21.4k g/mol for the PEO block was used to study the PEO crystal orientation changes at different crystallization temperatures (T{sub x}) via small- and wide-angle X-ray scattering techniques. For this diblock copolymer, an inverse hexagonal cylinder (IHC) phase morphology was identified with PS cylinders hexagonally packed within the PEO matrix. In this IHC morphology, the PEO blocks were tethered on the convex interfaces of the PS domains, and the crystallization of PEO blocks was outside of the cylinders. The crystal orientation ofmore » the PEO blocks (the c-axis of the PEO crystals) after crystallization among the PS cylinders was, for the first time, found to change with respect to the long cylinder axis, {cflx a}, depending solely on T{sub x}. At very low T{sub x}'s, when the samples were quenched into liquid nitrogen, the crystals possessed a random orientation. When -30 C {<=}T{sub x} {<=} 5 C, PEO crystals had an orientation with their c-axis parallel to {cflx a}. Within the temperature region of 10 C {<=} T{sub x} {<=} 20 C, the c-axis crystal orientation changed to be tilted with respect to {cflx a} (the tilting angle was defined to be between the c-axis of the PEO crystals and {cflx a}). This tilting angle increased with increasing T{sub x}. Finally, a major crystal orientation with the c-axes of PEO crystals perpendicular to {cflx a} was observed when Tx reached 30 C. Furthermore, it was particularly interesting that the PEO crystals in the IHC phase were oriented in two dimensions when T{sub x} = 30 C. Namely, the PEO crystal growth was specifically grown along the {l_brace}100{r_brace} planes of the hexagonal PS cylinders. The crystallite sizes were estimated by the Scherrer equation. The PEO crystal sizes, at least along one dimension, were on the scale of the sizes limited by the distance between the neighboring glassy PS cylinders in the hexagonal lattice.« less
  • A poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer with number-average molecular weights of 7.7k g/mol for the PS block and 21.4k g/mol for the PEO block was used to study the PEO crystal orientation changes at different crystallization temperatures (T{sub x}) via small- and wide-angle X-ray scattering techniques. For this diblock copolymer, an inverse hexagonal cylinder (IHC) phase morphology was identified with PX cylinders hexagonally packed within the PEO matrix. In this IHC morphology, the PEO blocks were tethered on the convex interfaces of the PS domains, and the crystallization of PEO blocks was outside of the cylinders. The crystal orientation ofmore » the PEO blocks (the c-axis of the PEO crystals) after crystallization among the PS cylinders was, for the first time, found to change with respect to the long cylinder axis, a, depending solely on T{sub x}. At very low T{sub x}'s, when the samples were quenched into liquid nitrogen, the crystals possessed a random orientation. When -30 {sup o}C {<=} T{sub x} {<=} 5 {sup o}C, PEO crystals had an orientation with their c-axis parallel to a. Within the temperature region of 10 {sup o}C < T{sub x} {<=} 20 {sup o}C, the c-axis crystal orientation changed to be tilted with respect to a (the tilting angle was defined to be between the c-axis of the PEO crystals and a). This tilting angle increased with increasing T{sub x}. Finally, a major crystal orientation with the c-axes of PEO crystals perpendicular to a was observed with T{sub x} reached 30 {sup o}C. Furthermore, it was particularly interesting that the PEO crystals in the IHC phase were oriented in two dimensions when T{sub x} = 30 {sup o}C. Namely, the PEO crystal growth was specifically grown along the {l_brace}1010{r_brace} planes of the hexagonal PS cylinders. The crystallite sizes were estimated by the Scherrer equation. The PEO crystal sizes, at least along on dimension, were on the scale of the sizes limited by the distance between the neighboring glassy PS cylinders in the hexagonal lattice.« less
  • No abstract prepared.
  • A poly(ethylene oxide)-{ital b}-polystyrene (PEO-{ital b}-PS) diblock copolymer having a number-average molecular weight ({bar M}{sub n}) of 11&hthinsp;000 g/mol in the PEO blocks and an {bar M}{sub n} of 5200 g/mol in the PS blocks has been synthesized (with a volume fraction of the PEO blocks of 0.66 in the molten state). Differential scanning calorimetry results show that this copolymer possesses a single endotherm, which is attributed to the melting of the PEO-block crystals. Based on real-time resolved synchrotron small-angle x-ray scattering (SAXS) observations, the diblock copolymer is in a disordered state above the glass transition temperature of the PS-richmore » phase (T{sub g}{sup PS}), which has been determined to be 44.0&hthinsp;{degree}C during cooling using dilatometer mode in thermomechanical measurements. The order-disorder transition temperature (T{sub ODT}) for this diblock copolymer is thus experimentally inaccessible. Depending upon different isothermal crystallization temperatures quenched from the disordered state (T{sub q}s), four cases can be investigated in order to understand the phase relationships among self-organization, crystallization of the PEO blocks, and vitrification of the PS-rich phase: the region where the T{sub q} is above the T{sub g}{sup PS}, the regions where the T{sub q} is near but slightly higher or lower than the T{sub g}{sup PS}; and the region where the T{sub q} is below the T{sub g}{sup PS}. Utilizing simultaneous SAXS and wide angle x-ray-diffraction experiments, it can be seen that lamellar crystals of the PEO blocks in the first case grow with little morphological constraint due to initial disordered phase morphology. As the T{sub q} approaches but is still slightly higher than the T{sub g}{sup PS}, as in the second case, the PEO-block crystals with a greater long period ({ital L}) than that of the disordered state start to grow. The initial disordered phase morphology is gradually destroyed, at least to a major extent. When the T{sub q} is near but slightly lower than the T{sub g}{sup PS}, the crystallization takes place largely within the existing phase morphology. Only a gradual shift of the {ital L} towards smaller {ital q} values can be found with increasing time, which implies that the initial phase morphology is disturbed by the crystallization of the PEO blocks. In the last case, the PEO blocks crystallize under a total constraint provided by the disordered phase morphology due to rapid vitrification of the PS-rich phase. Substantial decrease of crystallinity can be observed in this case. This study also provides experimental evidence that the PS-rich phase size, which is down to 7{endash}8 nm, can still retain bulky glassy properties. {copyright} {ital 1999} {ital The American Physical Society}« less