IEEE transactions on dielectrics and electrical insulation vol:8 issue:3 pages:365-372
Supramolecular polymers, which are non-covalently bonded and formed by self association of di or trifunctional monomers exhibit, by virtue of quadruple hydrogen bonds, many of the properties of normal high molecular weight polymers, e.g a dynamic rubber plateau. We focus on the molecular and cooperative dynamics of self-assembled linear polymers and networks, studied by broadband dielectric relaxation spectroscopy (DRs) in the frequency range from 10(-2) to 10(6) Hz. The Das analysis was backed up by dynamic mechanical and theological experiments. In the high temperature region two loss processes (alpha and alpha*) show up, the relaxation times of which obey the Vogel-Fulcher-Tammann (VFT) law. The dielectric cu process is related to the dynamic glass-rubber transition and is slightly faster than the corresponding mechanical or process. A slower (high-temperature) alpha* relaxation is identified as chemical corresponding to the mean lifetime of the hydrogen bonded linkages in the supramolecular chains. Its relaxation time tau (alpha*) was found to be 1 to 2 decades larger than the terminal now relaxation time, indicating that the relaxation of an entire chain is dominated by the joint dynamics of many hydrogen bonds. The beta relaxation, observed in both Das and dynamic mechanical analysis (DMA) at temperatures below T-g, arises from the local junction dynamics of hydrogen bonded units in the glassy state. Details of the temperature dependence and the shape of the loss peaks of the alpha and alpha* relaxations will be discussed in terms of temporary physical networks and cooperativity.