TY - JOUR
T1 - Thermodynamics and Structure of Poly[n]catenane Melts
AU - Rauscher, Phillip M.
AU - Schweizer, Kenneth S.
AU - Rowan, Stuart J.
AU - De Pablo, Juan J.
N1 - Funding Information:
The authors gratefully acknowledge Dr. Artem Rumyantsev, Prof. Michael A. Webb, Dr. Nicholas E. Jackson, and Cody T. Bezik for many helpful discussions. Special thanks to Dr. Rumyantsev for providing many insightful comments on an early version of this paper, and to Viviana Palacio-Betancur for the assistance with several figures. P.M.R. thanks the National Science Foundation (NSF) for the award of a Graduate Research Fellowship, Grant No. 1746045. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The theoretical and computational work presented here is supported by the Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Science and Engineering. Initial investigations of poly[ n]catenane systems were also supported by the NSF under Grant Nos. CHE-1402849 and CHE-1903603. K.S.S. thanks the Pritzker School of Molecular Engineering for financial support during his sabbatical stay at the University of Chicago. The development of materials for impact mitigation, of which poly[ n]catenanes represent a category, is supported by NIST through the Center for Hierarchical Materials Design (CHiMaD).
Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/5/12
Y1 - 2020/5/12
N2 - Motivated by recent achievements in the synthesis of interlocking polymers, the structural features of poly[n]catenanes, polymers composed entirely of interlocking rings (or macrocycles), are studied by extensive molecular dynamics simulations in the melt state. The degree of polymerization (number of links) is varied from n = 1-25 and the number of beads per macrocycle is varied from m = 15-50; the results are compared to linear chains of degrees of polymerization N = 15-175. The mechanical bonds in the system cause significant topological contributions to the pressure and potential energy density not seen in other polymer systems. The polymers themselves possess many unusual structural features at short and intermediate length scales, which can be attributed to density inhomogeneities along the polymer contour. Furthermore, the conformations of the individual macrocycles within poly[n]catenanes are quite different from those of ordinary ring polymers and depend on the topology of the macrocycle, that is, whether it is threaded by one ring (chain end) or two (chain center). At larger length scales, the poly[n]catenanes are conformationally similar to ideal linear chains, but unlike traditional (covalent) polymers, they are highly globular at low degrees of polymerization and are extremely flexible relative to their size, which inhibits interchain entanglement. Implications for poly[n]catenane material properties and synthesis are discussed.
AB - Motivated by recent achievements in the synthesis of interlocking polymers, the structural features of poly[n]catenanes, polymers composed entirely of interlocking rings (or macrocycles), are studied by extensive molecular dynamics simulations in the melt state. The degree of polymerization (number of links) is varied from n = 1-25 and the number of beads per macrocycle is varied from m = 15-50; the results are compared to linear chains of degrees of polymerization N = 15-175. The mechanical bonds in the system cause significant topological contributions to the pressure and potential energy density not seen in other polymer systems. The polymers themselves possess many unusual structural features at short and intermediate length scales, which can be attributed to density inhomogeneities along the polymer contour. Furthermore, the conformations of the individual macrocycles within poly[n]catenanes are quite different from those of ordinary ring polymers and depend on the topology of the macrocycle, that is, whether it is threaded by one ring (chain end) or two (chain center). At larger length scales, the poly[n]catenanes are conformationally similar to ideal linear chains, but unlike traditional (covalent) polymers, they are highly globular at low degrees of polymerization and are extremely flexible relative to their size, which inhibits interchain entanglement. Implications for poly[n]catenane material properties and synthesis are discussed.
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U2 - 10.1021/acs.macromol.9b02706
DO - 10.1021/acs.macromol.9b02706
M3 - Article
AN - SCOPUS:85082802794
VL - 53
SP - 3390
EP - 3408
JO - Macromolecules
JF - Macromolecules
SN - 0024-9297
IS - 9
ER -