Residual stress relaxation and stiffness in spin-coated polymer films: Characterization by ellipsometry and fluorescence

Askar, Shadid; Evans, Christopher M.; Torkelson, John M.

doi:10.1016/j.polymer.2015.08.036

Cited by 46 publications

(73 citation statements)

References 73 publications

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“…In agreement with previous dewetting studies to probe residual stress relaxation in thin polystyrene films, Askar et al found Arrhenius temperature dependence of stress relaxation times, having low activation energy comparable to a fast β‐like relaxation process . However, the T g of bulk PS films was unaffected by residual stress relaxation .…”

Section: Fluorescence To Measure Mechanical Responsesupporting

confidence: 88%

“…Although the ratio of the first to third vibronic peak intensities of the pyrenyl dye fluorescence spectra (displayed in Figure a) can be plotted against temperature to give T g (as shown for two different film thicknesses in Figure b), individual isothermal measurements of this ratio were found to be related to a “caging” mechanism involving sequential segmental motion of the polymer . This “caging” was further dependent on the stiffness and residual stress relaxation of the film …”

Section: Fluorescence To Measure Mechanical Responsementioning

confidence: 99%

“…[130] Using similar experimental approaches to those developed to determine T g [17,31] and structural relaxation [22] by fluorescence, Torkelson and co-workers recently investigated several aspects of residual stresses and stiffening in pyrenelabeled polystyrene single-layer films. [208,209] Although the ratio of the first to third vibronic peak intensities of the pyrenyl dye fluorescence spectra (displayed in Figure 14a) can be plotted against temperature to give T g (as shown for two different film thicknesses in Figure 14b), individual isothermal measurements of this ratio were found to be related to a "caging" mechanism involving sequential segmental motion of the polymer. [208] This "caging" was further dependent on the stiffness and residual stress relaxation of the film.…”

Section: Fluorescence To Measure Mechanical Responsementioning

confidence: 99%

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21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

Burroughs

Christie

Gray

et al. 2017

Macro Chemistry & Physics

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properties. [9,10] While fluorescence has been used extensively to characterize bulk properties of polymers, including glass transition temperature (T g ) [11][12][13] and polymerization conversion, [13] it is particularly well-suited to study polymers at the nanoscale. This is largely due to the fact that fluorescence techniques enable sensitive and location-specific measurements with high resolution.In this review, we focus on the use of both steady-state and transient fluorescence techniques to characterize physical properties of polymers over nanoscale dimensions. This length scale can refer to film thickness in single-component polymer films, interparticle spacing in nanocomposites, domain spacing in phaseseparated block copolymers, and distance from the polymer-polymer interface in multicomponent immiscible blends. Several geometries characterized via fluorescence are shown in Figure 1. Prior to delving into specific contributions, the basic principles and techniques of fluorescence are presented as well as a brief introduction to the behavior of confined polymers. We then present recent advances in fluorescence techniques for polymer physical characterization under confinement with regards to the glass transition temperature, physical aging, mobility and diffusion, and mechanical response. Through this examination of the literature, we illustrate the unique ability of fluorescence to characterize polymers in confined and complex geometries, providing insights into the influences of interfaces and nanostructure on material properties through sensitive, location-specific measurements. We conclude with a view toward future areas of research in which fluorescence has the potential to be impactful. Introduction to FluorescenceWhen a molecule absorbs energy via light, an electron is excited to a higher energy state, returning to the ground state through either radiative or nonradiative deactivation. This electronic excitation and return to the ground state is a combination of three photophysical processes: absorption, luminescence, and nonradiative decay. [33] Fluorescence is a luminescent process in which the excited-state electron returns to the ground state by emitting a photon, i.e., light. As shown in a simplified Jablonski Polymer CharacterizationCharacterization of polymers at the nanometer-length scale has become increasingly important with the growth and expansion of nanotechnology. Due to limitations of sensitivity and specificity that persist with traditional materials characterization techniques, there is a growing need to develop new tools to measure the properties of confined polymer systems. Within the past 20 years, fluorescence characterization techniques have emerged to address this challenge. This review focuses on the employment of fluorescence techniques such as temperature-and time-dependent steady-state intensity, fluorescence recovery after photobleaching, and nonradiative energy transfer to study polymer behavior at the nanoscale. Properties discussed include glass transition temperatur...

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Section: Fluorescence To Measure Mechanical Responsesupporting

confidence: 88%

Section: Fluorescence To Measure Mechanical Responsementioning

confidence: 99%

Section: Fluorescence To Measure Mechanical Responsementioning

confidence: 99%

See 1 more Smart Citation

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

Burroughs

Christie

Gray

et al. 2017

Macro Chemistry & Physics

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show abstract

“…where the values of ͗ u 2 ͘ are determined in the bulk at the bulk T g of the confi ned material and B is an adjustable parameter refl ecting the material's sensitivity to softness of confi nement. The success of ͗ u 2 ͘ as a measure of the softness of confi nement can be understood based upon a general scaling relationship between ͗ u 2 ͘, which is an experimentally accessible [68][69][70][71][72] measure of local segmental rattle space on a picosecond timescale, [ 73,74 ] and the high-frequency shear modulus,…”

Section: What Determines the Magnitude And Direction Of Interface Effmentioning

confidence: 99%

“…The success of ⟨ u 2 ⟩ as a measure of the softness of confinement can be understood based upon a general scaling relationship between ⟨ u 2 ⟩, which is an experimentally accessible measure of local segmental rattle space on a picosecond timescale, and the high‐frequency shear modulus,

G_{\infty} \propto k T / (u^{2})

. In essence, this result indicates that the dynamics of near‐interface polymers are more sensitive to interfacial energy when they are confined by a material exhibiting a relatively high glassy modulus.…”

Section: Introductionmentioning

confidence: 99%

An Emerging Unified View of Dynamic Interphases in Polymers

Simmons

2015

Macro Chemistry & Physics

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The properties of nanostructured polymeric materials reflect the presence of a dynamic interphase in which polymer segmental dynamics, glass formation, mechanics, and transport properties are altered from their bulk states. Examples include nanoconfinement effects on polymer nanofilms, reinforcement effects in polymer nanocomposites and filled rubbers, formation of a rigid amorphous fraction in semicrystalline polymers, and observation of suppressed‐mobility domains around ionic aggregates in ionomers. Whereas many of these phenomena have been viewed as emerging from system‐specific mechanisms, here recent work is highlighted that contributes to an emerging unified understanding of the dynamic interphase in all of these systems. This view suggests that the size scales of dynamic interphases in polymers are generally determined by the scale of cooperative rearrangements intrinsic to relaxation dynamics in supercooled glass‐forming liquids. It also implicates alterations in local segmental rattling as playing a central role in the dynamic interphase, and it suggests that near‐interface modifications in dynamics exhibit a general dependence on the interfacial work of adhesion and the relative high‐frequency moduli of the interface‐adjacent domains.

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Nonequilibrium Properties of Thin Polymer Films

Chandran¹,

Reiter²

2022

Macromolecular Engineering

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Rapid industrial processes often freeze polymers in nonequilibrium conformations, which, in turn, cause material properties that are significantly different from the predictions of equilibrium theories. Such deviations in properties may introduce enhanced material performance. Thus, by choosing appropriate processing pathways, we potentially can control macroscopic properties and performance of polymers. However, due to our current lack of fundamental understanding of the behavior of nonequilibrated polymers, we have to rely on empirical knowledge, imposing trial‐and‐error approaches for achieving desired properties. Considering these aspects, we discuss recent studies on polymer films revealing that quantitative relations exist between properties and processing pathways, suggesting possible relations for processing‐induced deviations in chain conformations. These relations propose that long‐living and long‐ranged correlations between polymers have been induced by processing, as indicated by the observation of relaxation times much longer than known for equilibrated polymers. We present an example where control of processing conditions for thin films allowed to translate the molecular relaxations during equilibration into a predictable lifting of macroscopic loads. Motivated by the presented results, we conclude that a comprehensive understanding of polymers with nonequilibrium conformations may not only expand the available spectrum of polymer properties but will also widen the scope of polymer science.

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Residual stress relaxation and stiffness in spin-coated polymer films: Characterization by ellipsometry and fluorescence

Cited by 46 publications

References 73 publications

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

An Emerging Unified View of Dynamic Interphases in Polymers

Nonequilibrium Properties of Thin Polymer Films

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