Sphere-to-cylinder transitions in thin films of diblock copolymers under shear: The role of wetting layers

Alexandros Chremos, Paul M. Chaikin, Richard A. Register, Athanassios Z. Panagiotopoulos

    Research output: Contribution to journalArticle

    Abstract

    Shear-induced sphere-to-cylinder transitions in diblock copolymer thin films have been studied using coarse-grained Langevin dynamics simulations. Parameters of the coarse-grained model were chosen to represent a polystyrene-polyisoprene copolymer with molecular weights of the blocks equal to 68 and 12 kg/mol, respectively, matching the system studied experimentally by Hong et al. [Soft Matter2009, 5, 1687]. At zero-shear conditions and below the order-disorder transition temperature, thin films form a monolayer or bilayer of spheres. The minority block has higher affinity for the confining surfaces, thus forming wetting layers whose chains interpenetrate those forming the microdomain layer(s). Once a shear field is applied and above a critical shear rate, the spheres elongate and merge with their neighbors to form cylinders. We find that shear-induced cylinder formation is closely related to stretching of individual diblock chains. Our simulations suggest that a higher stress is required to achieve the sphere-to-cylinder transition in monolayer versus bilayer thin films because the wetting layers transfer momentum into the film by stretching the chains, which in turn causes higher shear stress for a given surface velocity. This observation is in agreement with experimental findings. In addition to the effects of shear, the impact of temperature was investigated with respect to chain stretching and the formation of cylinders under shear.

    Original languageEnglish (US)
    Pages (from-to)4406-4415
    Number of pages10
    JournalMacromolecules
    Volume45
    Issue number10
    DOIs
    StatePublished - May 22 2012

    Fingerprint

    Block copolymers
    Wetting
    Stretching
    Thin films
    Monolayers
    Polyisoprenes
    Order disorder transitions
    Momentum transfer
    Polystyrenes
    Shear deformation
    Superconducting transition temperature
    Shear stress
    Copolymers
    Molecular weight
    Computer simulation
    Temperature

    ASJC Scopus subject areas

    • Organic Chemistry
    • Materials Chemistry
    • Polymers and Plastics
    • Inorganic Chemistry

    Cite this

    Chremos, A., Chaikin, P. M., Register, R. A., & Panagiotopoulos, A. Z. (2012). Sphere-to-cylinder transitions in thin films of diblock copolymers under shear: The role of wetting layers. Macromolecules, 45(10), 4406-4415. https://doi.org/10.1021/ma300382v

    Sphere-to-cylinder transitions in thin films of diblock copolymers under shear : The role of wetting layers. / Chremos, Alexandros; Chaikin, Paul M.; Register, Richard A.; Panagiotopoulos, Athanassios Z.

    In: Macromolecules, Vol. 45, No. 10, 22.05.2012, p. 4406-4415.

    Research output: Contribution to journalArticle

    Chremos, A, Chaikin, PM, Register, RA & Panagiotopoulos, AZ 2012, 'Sphere-to-cylinder transitions in thin films of diblock copolymers under shear: The role of wetting layers', Macromolecules, vol. 45, no. 10, pp. 4406-4415. https://doi.org/10.1021/ma300382v
    Chremos, Alexandros ; Chaikin, Paul M. ; Register, Richard A. ; Panagiotopoulos, Athanassios Z. / Sphere-to-cylinder transitions in thin films of diblock copolymers under shear : The role of wetting layers. In: Macromolecules. 2012 ; Vol. 45, No. 10. pp. 4406-4415.
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