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Segmental and crosslink point motion in networks
Author(s) -
Dickinson L. C.,
Chien J.C.W.,
MacKnight W. J.
Publication year - 1990
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19900340112
Subject(s) - relaxation (psychology) , viscoelasticity , materials science , dynamic mechanical analysis , isotropy , nuclear magnetic resonance , crystallography , molecular physics , polymer , chemistry , composite material , physics , optics , psychology , social psychology
13 C‐ and 31 P‐NMR spin lattice relaxation in the rotating frame have been measured on a series of networks prepared from monodisperse and deliberately bimodal poly(propylene glycols) (PPG) crosslinked with tris(4‐isocyanatophenyl) thiophosphate. The T 1 p C minima correspond to loss maxima in the DMTA (Dynamic Mechanical Testing) measured at 10Hz. The T 1 p P minima fall at higher temperatures than those of T 1 p C for the same network indicating that these crosslinks lag the segments in frequency of motion at a given temperature. The carbon relaxation is biphasic below T g of the segments indicating two relaxation domains which we assign to bulklike PPG segments and PPG segments proximal to he crosslink. Lineshape analysis by a diffusional model indicates crosslink reorientation is not isotropic until well above T g . Relaxation and lineshapes for the bimodal networks indicate that junctions are not uniformly plasticized by the segments.