da Silva LC, Bowers CR, Graf R, Wagener KB. Molecular Motion of the Junction Points in Model Networks Prepared by Acyclic Triene Metathesis.
Macromol Rapid Commun 2016;
37:527-31. [PMID:
26787457 DOI:
10.1002/marc.201500642]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 12/06/2015] [Indexed: 11/07/2022]
Abstract
The junction dynamics in a selectively deuterated model polymer network containing junctions on every 21st chain carbon is studied by solid state (2) H echo NMR. Polymer networks are prepared via acyclic triene metathesis of deuteron-labeled symmetric trienes with deuteron probes precisely placed at the alpha carbon relative to the junction point. The effect of decreasing the cross-link density on the junction dynamics is studied by introduction of polybutadiene chains in-between junctions. The networks are characterized by swelling, gel content, and solid state (1) H MAS NMR. Line shape analysis of the (2) H quadrupolar echo spectra reveals that the degree of motion anisotropy and the distribution of motion correlation times depend on the cross-link density and structural heterogeneity of the polymer networks. A detailed model of the junction dynamics at different temperatures is proposed and explained in terms of the intermolecular cooperativity in densely-packed systems.
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