Polymers in 2D confinement: A nanoscale mechanism for thermo-mechanical reinforcement
Por:
Romo-Uribe A.
Publicada:
1 ene 2018
Categoría:
Polymers and plastics
Resumen:
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, 2Rh ? d001, where Rh is the polymer's hydrodynamic radius and d001 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, ?Tg = Tg ? Tg,bulk ~ 10°C, and the dynamic modulus E? increased 10-fold. Analysis of dynamic mechanical spectra showed an increase of relaxation time ?, ie, polymer dynamics retardation. Furthermore, the mechanical damping tan ? was strongly attenuated evidencing the reduction of viscous dissipation. The activation energy Ea of the ?-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/Ematrix ~ (2Rh/d001)n. This study paves the road for further understanding of polymer dynamics under 2D confinement and the reinforcement mechanism of thermo-mechanical properties. Copyright © 2017 John Wiley & Sons, Ltd.
Filiaciones:
Romo-Uribe A.:
R&D, Advanced Science & Technology Division, Johnson & Johnson Vision, Jacksonville, FL, United States
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