Nanostructured Composites with Layered Morphology: Structure and Properties

Adhikari, Rameshwar; Henning, Sven; Michler, Goerg H.

doi:10.1002/masy.200690025

Cited by 14 publications

(3 citation statements)

References 16 publications

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“…Other recent studies of multilayer films have also shown large changes in properties with decreasing layer thickness. Hiltner and coworkers 3,4 have observed increased gas permeation and merging of the dynamics into a single T g when the thickness of the nanolayers is reduced, and Adhikari et al 5 have observed craze propagation across multiple layers when the layer thickness is decreased. Why do the cooperative segmental dynamics behave fundamentally different when the layer/domain thicknesses reach <∼10 nm?…”

Section: Comparison Of Block Copolymer Films To Multilayer Films Of D...mentioning

confidence: 99%

“…With recent advances in polymer processing yielding nanoscale layer or domain sizes, − there is potential for significant property improvements with important technological applications. For instance, multilayer films of different polymers are used in applications ranging from barrier layers for food packaging 9 to films with unique optical properties .…”

Section: Introductionmentioning

confidence: 99%

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Selectively Probing the Glass Transition Temperature in Multilayer Polymer Films: Equivalence of Block Copolymers and Multilayer Films of Different Homopolymers

2007

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The temperature dependence of the fluorescence of trace levels of pyrene was employed to measure the glass transition temperatures (T gs) of polystyrene (PS) domains within ultrathin films of poly(styrene-block-methyl methacrylate) (P(S-b-MMA)) and poly(styrene-block-2-vinylpyridine) (P(S-b-2VP)) diblock copolymers supported on silica after self-assembly into lamellar morphologies. The PS domains within the two block copolymers exhibited dramatically different T g−nanoconfinement behavior. The T gs of the PS domains within the P(S-b-MMA) films were observed to decrease with decreasing film thickness in accordance with T g reductions observed for single-layer PS homopolymer films; in contrast, the T g of the PS domains within the P(S-b-2VP) films exhibited no change within experimental uncertainty upon confinement. The T gs of the block copolymer films showed excellent agreement with those of multilayer films constructed from homopolymer layers with an equivalent morphology, indicating that chain connectivity across the immiscible interface has little impact on cooperative segmental dynamics within the individual layers/domains. The difference in the T g−nanoconfinement behavior exhibited by the PS free-surface layer of P(S-b-MMA) and P(S-b-2VP) block copolymer films, and equivalently exhibited by the PS free-surface layer of PS/PMMA and PS/P2VP bilayer films, is due to the much stronger attractive interaction at the P2VP−silica substrate interface. Once the P2VP−silica substrate interaction is removed, the P2VP underlayer is no longer able to suppress the enhanced mobility of a PS free-surface layer when the underlayer thickness is made sufficiently thin (<∼10 nm). This indicates that both the type and amount of material present in the underlayers determine the T g−nanoconfinement behavior at the free surface of multilayer films. In addition, intrinsic phenyl ring fluorescence was shown to be effective for quantifying in situ the time scale for self-assembly of styrene-containing block copolymers.

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Section: Comparison Of Block Copolymer Films To Multilayer Films Of D...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Selectively Probing the Glass Transition Temperature in Multilayer Polymer Films: Equivalence of Block Copolymers and Multilayer Films of Different Homopolymers

2007

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“…Other microlaminate systems such as the ductile/ductile polyethylene-terephthalate (PET)/PC and the brittle/brittle polystyrene (PS)/ PMMA have been discussed elsewhere(Ivan'kova et al, 2004a,b;Balta Calleja et al, 2005;Adhikari et al, 2006).2 Kerns et al (2000) used a gently waisted specimen geometry, shown inFig. 1(b), in their uni-axial experiments on PC/PMMA laminates, resulting in an axial stress that varies with axial position which, in turn, favors inelastic events to initiate at the minimum crosssection.…”

mentioning

confidence: 98%

Micromechanics of toughening in ductile/brittle polymeric microlaminates: Effect of volume fraction

Sharma

Boyce

Socrate

2008

International Journal of Solids and Structures

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Ductile/brittle microlaminates, comprised of alternating layers of ductile polymer [e.g., polycarbonate (PC)] that inelastically deform by shear yielding, and brittle polymer [e.g., styrene-acrylonitrile (SAN), polymethylmethacrylate (PMMA)] that undergo crazing in tension, offer a strategy for tensile toughening by capitalizing on the synergistic interactions between crazing and shear yielding. This work presents a micromechanical model for PC/PMMA ductile/brittle laminates that captures the constituent volume fraction dependence of the macroscopic behavior, as well as the underlying micro-mechanisms of deformation and tensile failure, in particular the synergy between crazing and shear yielding. The finite element implementation of the model considers both two-dimensional and three-dimensional representative volume elements (RVEs), and incorporates continuum-based physics-inspired descriptions of shear yielding and crazing, along with failure criteria for the ductile (PC) and brittle (PMMA) layers. The interface between the ductile and brittle layers is assumed to be perfectly bonded. The 3D RVE models successfully capture the macroscopic tensile stress-strain behavior of the ductile/brittle laminates at varying constituent volume fractions and the corresponding underlying micromechanisms of deformation and failure. The transition from brittle to ductile laminate behavior is in agreement with experimental data and is found to occur as the fraction of the ductile layer is increased to 0.60. The simulations reveal the brittle to ductile cross-over to be governed by the ability of the ductile layers to constrain the dilation and growth of crazes in the brittle layer. In particular, after the critical volume fraction of the ductile constituent is attained, surface edge crazes are inhibited from tunneling across the width of the specimen which then leads to reduced crazing/cracking and increased shear yielding. 2D RVE models are unable to adequately account for the deformation and toughness of PC/PMMA microlaminates as a function of the constituent volume fractions, as they neglect any distribution of inelastic events in the laminate-width (out-of-plane) direction.

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Micromechanical Properties

Šlouf

Henning

2022

Encyclopedia of Polymer Science and Technology

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The term micromechanical properties of polymers (or micromechanics of polymers) represents quite a broad topic, which comprises three principal areas: the measurement of micromechanical properties, the interpretation of micromechanical behavior, and the imaging of microstructure changes during deformation and fracture. Our contribution covers all three aspects of micromechanics in Polymer science. The first part focuses on the measurement of micromechanical properties by indentation methods, which dominate in the field of micromechanical properties measurement; the other micromechanical characterization methods are just mentioned briefly. The second part deals with the interpretation of micromechanical behavior, that is, with the correlations among molecular structure, supermolecular structure (morphology), micromechanical properties, and macromechanical properties of polymers. The third part describes imaging of microscopic processes during deformation and fracture or, in other words, how the deformation of polymer materials influences their morphology and vice versa.

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Nanostructured Composites with Layered Morphology: Structure and Properties

Cited by 14 publications

References 16 publications

Selectively Probing the Glass Transition Temperature in Multilayer Polymer Films: Equivalence of Block Copolymers and Multilayer Films of Different Homopolymers

Selectively Probing the Glass Transition Temperature in Multilayer Polymer Films: Equivalence of Block Copolymers and Multilayer Films of Different Homopolymers

Micromechanics of toughening in ductile/brittle polymeric microlaminates: Effect of volume fraction

Micromechanical Properties

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