Detection of Surface-Immobilized Components and Their Role in Viscoelastic Reinforcement of Rubber–Silica Nanocomposites

Mujtaba, Anas; Keller, M.; Ilisch, S.; Radusch, Hans‐Joachim; Beiner, Mario; Thurn‐Albrecht, Thomas; Saalwächter, Kay

doi:10.1021/mz500192r

Cited by 148 publications

(165 citation statements)

References 38 publications

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“…Percolation of the polymer with altered dynamics around NPs and their assemblies (as depicted in Fig. b) in polymers above T g is suggested to be the main reason for the nonclassical stiffening of PNCs by numerous authors . For instance, Tauban et al simulated the mechanical response of PNCs with retarded polymer segments within the particle structures of various morphologies based on previous experimental and theoretical results .…”

Section: Resultsmentioning

confidence: 99%

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Zbončák

Ondreáš

Uhlíř

et al. 2019

Polymer Engineering & Sci

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Structuring of polymer nanocomposites (PNCs) with an aid of relatively weak external magnetic fields has been studied as a method for control of the nano‐ and microstructure. Magnetic nanoparticles (NPs) were assembled into high aspect ratio one‐dimensional strings and unidirectionally oriented with the magnetic field (B = 0–50 mT) within the photopolymer matrix. The effect of the anisotropic MNPs assemblies on the mechanical properties was studied over a wide temperature range for the first time. The impact of various reinforcing mechanisms was distinguished with respect to the position of the glass transition temperature (Tg). The reinforcing effect exhibits temperature dependency with a maximum ~65°C above the glass transition and only negligible effect below the Tg. In addition, significant directional anisotropy of stiffness was observed. Composite micromechanics was applied to interpret the orientation and size‐dependent reinforcement of PNCs, and temperature‐dependent stiffness of the polymer‐MNP structures was quantified. The presence of polymer chains with altered dynamics surrounding the MNPs inside the anisotropic assemblies was proposed to be an essential nanoscale mechanism mediating the stress transfer and contributing to mechanical robustness of the hybrid structures and PNCs. POLYM. ENG. SCI., 60:587–596, 2020. © 2019 Society of Plastics Engineers

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Section: Resultsmentioning

confidence: 99%

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Zbončák

Ondreáš

Uhlíř

et al. 2019

Polymer Engineering & Sci

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“…1 The unique reinforcement has been explained theoretically 2,3 as well as experimentally [4][5][6] by filler networking, where filler-filler contacts are mediated by adsorbed and thus immobilized polymer species. The characterization of such adsorbed layers is challenging, as the traditional solvent-leaching technique ("bound rubber determination") largely overestimates the amount of polymer being part of the actual reduced-mobility layer.…”

Section: Introductionmentioning

confidence: 99%

Reduced-mobility layers with high internal mobility in poly(ethylene oxide)–silica nanocomposites

Golitsyn

Schneider

Saalwächter

2017

The Journal of Chemical Physics

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A series of poly(ethylene oxide) nanocomposites with spherical silica was studied by proton NMR spectroscopy, identifying and characterizing reduced-mobility components arising from either roomtemperature lateral adsorption or possibly end-group mediated high-temperature bonding to the silica surface. The study complements earlier neutron-scattering results for some of the samples. The estimated thickness of a layer characterized by significant internal mobility resembling backbone rotation ranges from 2 nm for longer (20 k) chains adsorbed on 42 nm diameter particles to 0.5 nm and below for shorter (2 k) chains on 13 nm particles. In the latter case, even lower adsorbed amounts are found when hydroxy endgroups are replaced by methyl endgroups. Both heating and water addition do not lead to significant changes of the observables, in contrast to other systems such as acrylate polymers adsorbed to silica, where temperature-and solvent-induced softening associated with a glass transition temperature gradient was evidenced. We highlight the actual agreement and complementarity of NMR and neutron scattering results, with the earlier ambiguities mainly arising from different sensitivities to the component fractions and the details of their mobility.

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“…Nanostructured films obtained from grafted nanoparticles (gold or SiO 2 ) dispersed in a polymer in solution have also been studied to understand the influence of nanoparticle‐matrix interactions on the thermal properties (note that tuning the length of the grafted chains promoted or not interactions with the polymer matrix) . Polymer nanofiller interaction has emerged as another important factor to explain the enhancement of physical properties in polymer nanocomposites, for instance, ionic interactions and van der Waals interactions …”

Section: Introductionmentioning

confidence: 99%

Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

Romo-Uribe

2017

Polymers for Advanced Techs

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Acrylate-clay nanocomposites, a 2D confined system, exhibited unusual increase of thermo-mechanical properties. The nature of this reinforcement can be ascribed to chain dynamics modification and therefore investigated via dynamic mechanical analysis. Transmission electron microscopy and dynamic light scattering showed a strong nanoconfined regime, 2R h ≫ d 001 , where R h is the polymer's hydrodynamic radius and d 001 is the clay gallery spacing.The geometrical constraints to polymer dynamics led to significant enhancement of the thermo-mechanical properties. Adding only 1 wt% nanoclay, the glass transition temperature increased significantly, ΔT g = T g − T g,bulk~1 0°C, and the dynamic modulus E′ increased 10-fold.Analysis of dynamic mechanical spectra showed an increase of relaxation time τ, ie, polymer dynamics retardation. Furthermore, the mechanical damping tan δ was strongly attenuated evidencing the reduction of viscous dissipation. The activation energy E a of the α-transition increased as the confined macromolecules needed to overcome higher energy barriers to achieve configurational rearrangements. The considerable increase of mechanical modulus cannot be explained by polymer composite models, rather it was associated to a "nano-effect," scaling with the degree of confinement as E/E matrix~( 2R h /d 001 )n . This study paves the road for further understanding of polymer dynamics under 2D confinement and the reinforcement mechanism of thermo-mechanical properties. 1-3 Hybrid nanoparticles are also successful to produce nanocomposites with more robust physical properties and are also being used to produce smart, shape memory polymeric networks with tailored thermo-mechanical properties. 4,5The addition of nanoclays, ie, layered silicates, to glassy and semicrystalline polymers has produced nanocomposites with enhanced mechanical, thermal, and barrier properties. For recent reviews, see Paul and Robeson 3 and Ray and Okamoto. 6 It is noted however that polymers (glassy and semicrystalline) with nanoclay concentrations in excess of 10 wt% led to relatively modest enhancement of mechanical properties, and the degree of property enhancement varies broadly according to the type of nanoclay used and the surface treatment. Furthermore, the concentration of nanoclays used also varies greatly and higher concentrations (>10%) appear contrary to the assumption that rather small concentrations of nanofiller would enhance the physical properties. 2,3It is believed that the macromolecular nanoconfinement found in, for instance, intercalated morphologies of layered silicate nanocomposites would be responsible to a larger extent for the changes of thermomechanical properties. For instance, confinement has induced lowering or increasing of the glass transition temperature, T g , in glassy polymer nanocomposites. The reduction of T g in confined small molecule glassy materials was first documented by McKenna et al. 7 The confinement in polymer nanocomposites is understood as (1) polymer chains constrained to layere...

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Detection of Surface-Immobilized Components and Their Role in Viscoelastic Reinforcement of Rubber–Silica Nanocomposites

Cited by 148 publications

References 38 publications

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Reduced-mobility layers with high internal mobility in poly(ethylene oxide)–silica nanocomposites

Polymers in 2D confinement: A nanoscale mechanism for thermo‐mechanical reinforcement

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