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Title: Rouse mode analysis of chain relaxation in polymer nanocomposites

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. Furthermore, 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.
 [1] ;  [2] ;  [3] ;  [4]
  1. Columbia Univ., New York, NY (United States). Dept. of Chemical Engineering; National Inst. of Technology Karnataka, Surathkal (India). Dept. of Chemical Engineering
  2. Columbia Univ., New York, NY (United States). Dept. of Chemical Engineering
  3. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Chemistry
  4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Report Number(s):
SAND-2015-2617J; SAND2014-19679J
Journal ID: ISSN 1744-683X; SMOABF; 581967
Grant/Contract Number:
AC04-94AL85000; AC02-05CH11231; DMR-1006514; DMR-1309892; DMR-1436201; DMR-1121107; DMR-1122483; 1-P01-HL108808-01A1
Accepted Manuscript
Journal Name:
Soft Matter
Additional Journal Information:
Journal Volume: 11; Journal Issue: 20; Journal ID: ISSN 1744-683X
Royal Society of Chemistry
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Columbia Univ., New York, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); National Inst. of Health (NIH) (United States); Cystic Fibrosis Foundation (United States)
Contributing Orgs:
Univ. of North Carolina, Chapel Hill, NC (United States); National Inst. of Technology Karnataka, Surathkal (India)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1340251