Brillouin scattering studies of polymeric nanostructures *

Hartschuh, R. D.; Ding, Yifu; Roh, Joon Ho; Kisliuk, A.; Sokolov, Alexei P.; Soles, Christopher L.; Jones, Ronald L.; Hu, Tianyi; Wu, Wen‐Li; Mahorowala, Arpan P.

doi:10.1002/polb.10780

Cited by 40 publications

(42 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…BLS measurements have shown limited impact of confinement on linear PS and PMMA thin films. These results are consistent with the invariant modulus generally obtained for nanostructures using BLS . One potential explanation for the limited impact of confinement is the time scale associated with the BLS measurement due to the frequency of the radiation.…”

Section: Elastic Properties Of Polymer Glasses Under Confinementsupporting

confidence: 90%

Mechanical and viscoelastic properties of confined amorphous polymers

Vogt

2017

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

Confinement of polymers to nanoscale dimensions can dramatically impact their physical properties. Substantial efforts have focused on the glass transition temperature (T g ) of polymers confined to thin films, but their mechanical properties are less studied despite their technological importance. In this review, challenges with mechanical measurements of polymer thin films are discussed along with novel metrologies that provide insight into their mechanical properties. A comparison of experimental measurements, simulations and theory provide several general conclusions about the mechanical properties under confinement. Confinement impacts the elastic modulus, rubbery compliance and viscosity of polystyrene, the archetypal polymer for confinement, but the confinement effect appears to depend on the measurement technique. This effect may be due to the details of averaging of gradients in properties that are dependent on the measurement details. Routes to minimize confinement effects are addressed. Despite progress in the measurements of mechanical properties of polymer thin films, there remain unresolved questions about the impact of confinement, which we highlight at the end of this review. 1,2 These concerns persist for polymeric nanostructures, where mechanical properties are critical to feature stability. 3 The mechanical properties of many polymers are dependent on their processing history,

show abstract

Section: Elastic Properties Of Polymer Glasses Under Confinementsupporting

confidence: 90%

Mechanical and viscoelastic properties of confined amorphous polymers

Vogt

2017

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

show abstract

“…The latter follows by ignoring F B in Eq. (7) and assuming K 0 (z) ∼ K 0,bulk , from which one can analytically derive an approximate inverse in distance variation from the surface behavior Figure 8 was used, while "simulation timescale" curve only fits the first 5 decades of data in Figure 8 to extract an exponent. Inset: Natural log-linear plot of the decoupling exponent versus location in the thick film.…”

Section: Interfacial Dynamic Decouplingmentioning

confidence: 99%

Dynamic Gradients, Mobile Layers, T_g Shifts, Role of Vitrification Criterion, and Inhomogeneous Decoupling in Free-Standing Polymer Films

Phan

Schweizer

2018

Macromolecules

View full text Add to dashboard Cite

The force-level Elastically Collective Nonlinear Langevin Equation (ECNLE) theory of activated relaxation in glass-forming free standing thin films is re-visited to improve its treatment of collective elasticity effects. The naive cut off of the isotropic bulk displacement field approximation is improved to explicitly include some aspects of spatial anisotropy with a modified boundary condition consistent with a step function liquid-vapor interface. The consequences of this improvement on dynamical predictions are quantitative but of significant magnitude, and in the direction of further speeding up dynamics and further suppressing T g . The theory is applied to thin films and also (for the first time) semi-infinite thick films to address qualitatively new questions for three different polymers of different dynamic fragility. Variation of the vitrification time scale criterion over many orders of magnitude is found to have a surprisingly minor effect on changes of the film-averaged T g relative to its bulk value. The mobile layer length scale grows strongly with cooling, and correlates in a nearly linear manner with the effective barrier deduced from the corresponding bulk isotropic liquid alpha relaxation time. The theory predicts a new type of spatially inhomogeneous "dynamic decoupling" corresponding to an effective factorization of the total barrier into its bulk temperature-dependent value multiplied by a function that only depends on location in the film. The effective decoupling exponent grows monotonically as the vapor surface is approached. Larger reductions of the absolute value of Tg shifts in thin polymer films are predicted for longer time vitrification criteria and more fragile polymers. Quantitative no-fit-parameter comparisons with experiment and simulation for film-thickness-dependent T g shifts of polystyrene and polycarbonate (PC) are in reasonable accord with the theory, including a nearly 100 Kelvin suppression of T g in 4 nm PC films. Predictions are made for polyisobutylene thin films.

show abstract

“…11 There are also recent examples in the literature of experimental methods for measuring the mechanical properties of thin and ultrathin polymer films, 5,12,13 the most prevalent being Brillouin light scattering (BLS). BLS has been used to measure the elastic constants of both supported 14,15 and free-standing 16 polymer films and features with thicknesses from 375 nm down to 29 nm, and it was observed that the high-frequency mechanical properties did not significantly change at these dimensions. Probing thinner free-standing films with BLS becomes difficult due to sample preparation and handing issues, while BLS measurements on thinner supported films are complicated by the presence of the substrate interface.…”

mentioning

confidence: 99%

Elastic Moduli of Ultrathin Amorphous Polymer Films

et al. 2006

View full text Add to dashboard Cite

The elastic moduli of ultrathin poly(styrene) (PS) and poly(methylmethacrylate) (PMMA) films of thickness ranging from 200 nm to 5 nm were investigated using a buckling-based metrology. Below 40 nm, the apparent modulus of the PS and PMMA films decreases dramatically, with an order of magnitude decrease compared to bulk values for the thinnest films measured. We can account for the observed decrease in apparent modulus by applying a composite model based on the film having a surface layer with a reduced modulus and of finite thickness. The observed decrease in the apparent modulus highlights issues in mechanical stability and robustness of sub-40 nm polymer films and features.

show abstract

Brillouin scattering studies of polymeric nanostructures *

Cited by 40 publications

References 18 publications

Mechanical and viscoelastic properties of confined amorphous polymers

Mechanical and viscoelastic properties of confined amorphous polymers

Dynamic Gradients, Mobile Layers, T_g Shifts, Role of Vitrification Criterion, and Inhomogeneous Decoupling in Free-Standing Polymer Films

Elastic Moduli of Ultrathin Amorphous Polymer Films

Contact Info

Product

Resources

About

Brillouin scattering studies of polymeric nanostructures *

Cited by 40 publications

References 18 publications

Mechanical and viscoelastic properties of confined amorphous polymers

Mechanical and viscoelastic properties of confined amorphous polymers

Dynamic Gradients, Mobile Layers, Tg Shifts, Role of Vitrification Criterion, and Inhomogeneous Decoupling in Free-Standing Polymer Films

Elastic Moduli of Ultrathin Amorphous Polymer Films

Contact Info

Product

Resources

About

Dynamic Gradients, Mobile Layers, T_g Shifts, Role of Vitrification Criterion, and Inhomogeneous Decoupling in Free-Standing Polymer Films