A coarse-grained model has been built to study the effect of the interfacial
interaction between spherical filler particles and polymer on the mechanical properties of
polymer nanocomposites. The polymer is modeled as bead-spring chains, and nano-fillers
grafted with coupling agent are embedded into the polymer matrix. The potential parameters
for polymer and filler are optimized to maximally match styrene-butadiene rubber reinforced
with silica particles. The results indicated that, to play a noticeable role in mechanical
reinforcement, a critical value exists for the grafting density of the filler–polymer coupling
agent. After reaching the critical value, the increase of grafting density can substantially
enhance mechanical properties. It is also observed that the increase of grafting density does not
necessarily increase the amount of independent polymer chains connected to fillers. Instead, a
significant amount of increased grafting sites serve to further strengthen already connected
polymer and filler, indicating that mechanical reinforcement can occur through the locally
strengthened confinement at the filler–polymer interface. These understandings based on
microstructure visualization shed light on the development of new filler polymer interfaces
with better mechanical properties.
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Structural Insight in the Interfacial Effect in Ferroelectric Polymer Nanocomposites
Both experimental results and theoretical models suggest the decisive role of the filler–matrix interfaces on the dielectric, piezoelectric, pyroelectric, and electrocaloric properties of ferroelectric polymer nanocomposites. However, there remains a lack of direct structural evidence to support the so‐called interfacial effect in dielectric nanocomposites. Here, a chemical mapping of the interfacial coupling between the nanofiller and the polymer matrix in ferroelectric polymer nanocomposites by combining atomic force microscopy–infrared spectroscopy (AFM–IR) with first‐principles calculations and phase‐field simulations is provided. The addition of ceramic fillers into a ferroelectric polymer leads to augmentation of the local conformational disorder in the vicinity of the interface, resulting in the local stabilization of the all‐
- Award ID(s):
- 1744213
- NSF-PAR ID:
- 10455153
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 32
- Issue:
- 49
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Polymer‐clay nanocomposites (PCNs) are commonly applied as multi‐functional structural materials with exceptional thermomechanical properties, while maintaining the characteristics of lightweight and optical clarity. In this study, building upon previously developed coarse‐grained (CG) models for nanoclay and poly (methyl methacrylate) (PMMA), we employ molecular dynamics (MD) simulations to systematically investigate the thermomechanical properties of PCNs when arranged in stacked configurations. Incorporating stacked clay nanofillers into a polymer matrix, we systematically conduct shear and tensile simulations to investigate the influences of variations in weight percentage, system temperature, and nanoclay size on the thermomechanical properties of PCNs at a fundamental level. The weight percentage of nanoclay in nanocomposites proves to have a significant influence on both the shear and Young's modulus (e.g., the addition of 10 Wt% nanoclay leads to an increase of 32.6% in the Young's modulus), with each exhibiting greater mechanical strength in the in‐plane direction compared to the out‐of‐plane direction, and the disparity between these two directions further widens with an increase in the weight percentage of nanoclay. Furthermore, the increase in the size of nanoclay contributes to an overall modulus enhancement in the composite while the growth reaches a saturation point after a certain threshold of about 10 nm. Our simulation results indicate that the overall dynamics of PMMA are suppressed due to the strong interactions between nanoclay and PMMA, where the confinement effect on local segmental dynamics of PMMA decays from the nanoclay‐polymer interface to the polymer matrix. Our findings provide valuable molecular‐level insights into microstructural and dynamical features of PCNs under deformation, emphasizing the pivotal role of clay‐polymer interface in influencing the thermomechanical properties of the composite materials.
Highlights CG modeling is performed to explore the thermomechanical behavior of PCN.
Effects of nanoclay weight percentage and size on modulus are studied.
Interface leads to nanoconfinement effect on
T gand molecular stiffness.Correlations between molecular stiffness and modulus are identified.
Simulations show spatial variation of dynamical heterogeneity.
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