Macromolecule and Particle Dynamics in Confined Media

Abstract

Dynamic properties play an important role in designing functional polymer nanocomposites, impacting molecular transport and phase separation kinetics. When nanoparticle (NP) size is comparable to polymer chain size, segmental relaxations may be influenced by changes in chain conformations and packing at the polymer/NP interface. Following the reptation model, these changes can perturb the longest relaxation time, in particular, the center-of-mass (COM) dynamics of polymer chains in entangled melts. This Perspective focuses on unsolved issues in polymer COM diffusion and local dynamics and segmental motions in the presence of NPs. The article introduces the effect of NP size, shape, surface modification, and enthalpic interactions on polymer diffusion and further relates dynamic studies in PNCs to macromolecular transport in bio-related systems and nanopores. Studies of local dynamics also provide insights into how entanglement density, monomeric friction, and chain conformation are influenced by NPs and how the interplay between these key parameters relates to COM dynamics to provide a unified picture across length scales. Moving forward, new studies investigating dynamics in PNCs are needed to address these unresolved problems and motivate potential applications from membranes for separations to NP carriers for drug delivery.

Co‐(POSS#‐styrene) nanocomposites reduced the glass‐transition temperature, rubbery modulus, and melt viscosity of entangled polystyrene

“…The reduction of T g and considerable decrease of melt viscosity suggest that the POSS # ‐sty copolymers induced changes to the macromolecular dynamics, perhaps due to nanoparticle‐induced chain disentanglement and free volume increase effects . The dynamics of the PS/POSS # ‐sty blends were investigated by probing the linear viscoelastic behavior using shear rheometry.…”

Polymer and spherical nanoparticle diffusion in nanocomposites

“…However, in polymer nanocomposites 2 there are more topological constraints due to the dispersed nanoparticles (NPs) in the polymer matrix that can influence the polymer primitive path [3][4][5][6][7] , thus the polymer dynamics. Polymer dynamics can be altered by the characteristics of nanoparticles such as size, shape, aspect ratio, surface area, volume fraction of nanoparticles and the nature of the interactions between the nanoparticle and the polymer matrix 8,9 . There are several theories that have been used to predict how the polymer diffusivity is impeded by impenetrable particles [10][11][12][13][14][15][16][17][18][19] .…”

Grafted polymer chains suppress nanoparticle diffusion in athermal polymer melts

“…3 Improved mechanical properties 4 and flammability 5 have also been achieved by adding NPs that impart strength and limit combustion, respectively, to the host polymer. In addition to adding functionality to polymers, nanoparticle mobility influences fundamental properties of the PNC such as melt flow and viscosity, [6][7][8][9][10][11] as well as the effectiveness of self-healing materials to limit crack propagation. 12 Therefore, an improved understanding of nanoparticle diffusion in polymer melts is of both technological and fundamental importance.…”