Year: 2015
Type: article
Abstract: Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.
Source: Soft Matter
DOI: 10.1039/c5sm00754b
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Funders: National Science Foundation, U.S. Department of Energy, Cystic Fibrosis Foundation, Center for Integrated Nanotechnologies, National Energy Research Scientific Computing Center, National Institutes of Health, Office of Science, National Nuclear Security Administration, National Heart, Lung, and Blood Institute, Division of Materials Research, Basic Energy Sciences, Advanced Scientific Computing Research, Sandia National Laboratories
Awards: G1071216263, G122673668, G1286236842, G1286251239, Triangle Center for Excellence for Materials Research and Innovation: Programmable Assembly of Soft Matter, G1414775356, G1445641779, G1591330662, G1677143136, G1799333409, G1816284028, G1863003419, G1867850364, DMREF/Collaborative Research: Acoustically Transformative Materials, G194215011, G2075401295, G2259352651, G237582453, G2472858983, G2815991194, G2900453181, G30714459, G3083819904, G3144391755, G351415096, G365575497, G37756661, G382641700, G419881185, G42916606, G4501827968, G498139845, G5076365615, MIRT: Stressed Polymers - Exploiting Tension in Soft Matter, G5296923526, G5375843722, G5849692847, G6485281451, G650090426, G6765930142, G7164875514, Dynamical Coupling Between Particles and Polymers, G7202702891, G7318852158, Development of Novel Mycolytic Therapies for Lung Disease, G805243471, G8315917632, G8456466421, G85740837, G866554245, G875654730, Collaborative: Viscoelasticity of Nanoparticle Dispersed Polymer Melts: Experiment and Simulation, G9000181756, G969889393
OpenAlex ID: W2159336807