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Volumn 81, Issue 1, 2010, Pages

Shear alignment and realignment of sphere-forming and cylinder-forming block-copolymer thin films

Author keywords

[No Author keywords available]

Indexed keywords

BLOCK COPOLYMER THIN FILMS; HEXAGONAL LATTICE; LATTICE ORDERS; MICRO-DOMAINS; MICRODOMAIN; MISORIENTATION ANGLE; MONODOMAINS; PHENOMENOLOGICAL MODELS; SHEAR ALIGNMENT; SHEAR DIRECTION; SINGLE LAYER; STRUCTURED FLUIDS; TWO LAYERS; VARIABLE STRESS;

EID: 76149145019     PISSN: 15393755     EISSN: 15502376     Source Type: Journal    
DOI: 10.1103/PhysRevE.81.011503     Document Type: Article
Times cited : (48)

References (43)
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    • Some previous reports employed a similar model wherein T ODT □ possessed a quadratic dependence on σ rather than the linear dependence employed here and in Ref.. The quadratic dependence should hold at the lowest shear rates due to requirements of analyticity and symmetry. However, the coupling of the microdomains to the shearing field should occur quickly and can cause this relationship to become linear as shear rate and thus stress is increased, especially for high molecular weight polymers [10.1063/1.470747
    • Some previous reports employed a similar model wherein T ODT □ possessed a quadratic dependence on σ rather than the linear dependence employed here and in Ref.. The quadratic dependence should hold at the lowest shear rates due to requirements of analyticity and symmetry. However, the coupling of the microdomains to the shearing field should occur quickly and can cause this relationship to become linear as shear rate and thus stress is increased, especially for high molecular weight polymers [A. I. Nakatani, J. Chem. Phys. 104, 1589 (1996)]. As a practical matter, it is difficult to determine the precise functional form of T ODT □ from the data presented here. Indeed, we have refit all the data using a quadratic dependence of T ODT □ on σ and while the values of σc necessarily differ, the general quality of the fits is similar. Most importantly, the finding presented herein that the cylinder-forming diblock can be satisfactorily described by a single value of σc (whether for alignment from a polygrain structure or realignment of the oriented structure), while the sphere-forming diblock requires a higher σc for realignment than initial alignment, is independent of the functional form assumed for T ODT □. 10.1063/1.470747
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    • A block copolymer's TODT in a thin film can differ from its TODT in bulk because of substrate and free-surface effects. The TODT for a film of PS-PEP 3/23 containing a single layer of spherical microdomains was previously measured to be 125°C versus the bulk value of TODT =121±2°C. We were unable to measure the thin film TODT for the PS-PEP 4/13 because of the rapid formation of large grains, but we expect it to be similarly close to the bulk TODT since it has the same block chemistry and wetting conditions as the sphere former. We chose to consistently use the bulk TODT values because they are available for both polymers, but as a practical matter, using a slightly different value for TODT in our fits would simply change the best-fit value of the critical stress slightly (not beyond our quoted uncertainties) and would not affect our discussion or conclusions.
    • A block copolymer's TODT in a thin film can differ from its TODT in bulk because of substrate and free-surface effects. The TODT for a film of PS-PEP 3/23 containing a single layer of spherical microdomains was previously measured to be 125°C versus the bulk value of TODT =121±2°C. We were unable to measure the thin film TODT for the PS-PEP 4/13 because of the rapid formation of large grains, but we expect it to be similarly close to the bulk TODT since it has the same block chemistry and wetting conditions as the sphere former. We chose to consistently use the bulk TODT values because they are available for both polymers, but as a practical matter, using a slightly different value for TODT in our fits would simply change the best-fit value of the critical stress slightly (not beyond our quoted uncertainties) and would not affect our discussion or conclusions.
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    • Ph.D. thesis, Princeton University
    • M. W. Wu, Ph.D. thesis, Princeton University, 2005.
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    • See supplementary material at http://link.aps.org/supplemental/10.1103/ PhysRevE.81.011503 for color-scale versions of figures.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.