Melt State Reinforcement of Polyisoprene by Silica Nanoparticles Grafted with Polyisoprene

Abstract

We systematically vary the nanoparticle (NP) dispersion state in composites formed by mixing polyisoprene homopolymers with polyisoprene grafted silica particles, and demonstrate how creep measurements allow us to overcome the limitations of small amplitude oscillatory shear (SAOS) experiments. This allows us to access nearly 13 orders in time in the mechanical response of the resulting composites. We find that a specific NP morphology, a percolating particle network achieved at intermediate graft densities, significantly reinforces the system and has a lower NP percolation loading threshold relative to other morphologies. These important effects of morphology only become apparent when we combine creep measurements with SAOS reemphasizing the role of synergistically combining methods to access the mechanical properties of polymer nanocomposites over broad frequency ranges.

Assembly of Polymer-Grafted Nanoparticles Dictates the Topological Constraints on Grafted Chains

“…In NC-5k samples, storage and loss moduli appear to reach another plateau which is commonly observed in the literature for jammed colloidal systems. , As the polymer fraction is low in case of the NC-5k sample, they exhibit these features similar to soft colloidal glasses. , However, for NC-12k, G ′ and G ″ decrease with a decrease in frequency with a similar power law. This could be interpreted as a sample approaching percolated network behavior due to a higher volume fraction of the polymer in NC-12k samples. , One possible interpretation could be that the absence of polymer entanglements in NC-5k would lead to more prominent interactions between the nanoparticles. However, in NC-12k, the weak entanglements in the grafted chains could screen these nanoparticle–nanoparticle interactions.…”

“…This could be interpreted as a sample approaching percolated network behavior due to a higher volume fraction of the polymer in NC-12k samples. 47,48 One possible interpretation could be that the absence of polymer entanglements in NC-5k would lead to more prominent interactions between the nanoparticles. However, in NC-12k, the weak entanglements in the grafted chains could screen these nanoparticle− nanoparticle interactions.…”

Manipulating the Void Nucleation and Propagation in Silica Nanoparticle/Polyisoprene Nanocomposites via Grafted Chains: A Multiscale Simulation

“…D g varies from 0.0 to 0.55, which is within the experimental range (0−0.6). 52,53 The grafting positions are evenly distributed on the surface of NPs according to the Fibonacci lattice 54 as shown in Figure S3, which can avoid the slip of grafted chains on the NP surface. Subsequently, each model is equilibrated for 100 ns at high T = 500 K and P = 0.1 MPa due to the low mobility of NPs, 50,55 which is then cooled to T = 300 K for 100 ns.…”

Addressing Nanocomposite Systems via 3D-SCFT: Assessment of Smearing Approximation and Irregular Grafting Distributions

“…Polymer-grafted nanoparticles (PGNPs) are quite promising for the manufacturing of membrane − and composite materials − for gas separation, biological, , mechanical reinforcement, − and optical applications . Theoretical frameworks and computer simulations are very useful in guiding and interpreting experimental studies and help resolve major design issues of industrial interest. ,− A variety of theoretical and simulation methodologies have been employed to address systems of PGNPs and brushes, such as the polymer reference interaction site model (PRISM), self-consistent field theory (SCFT), − density functional theory (DFT), − molecular dynamics (MD), − dissipative particle dynamics (DPD), − as well as machine-learning frameworks. , In addition to these studies, scaling laws for the height of the polymer brush have been proposed to describe the structural behavior of grafted chains in the solid/polymer interfacial region over a broad range of experimental conditions. ,− …”