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Complex dynamics of hydrogen bonded self-assembling polymers
- Source :
- IEEE Transactions on Dielectrics and Electrical Insulation, 8(3), 365-372. Institute of Electrical and Electronics Engineers, IEEE Transactions on Dielectrics and Electrical Insulation, 8 (3)
- Publication Year :
- 2001
- Publisher :
- Institute of Electrical and Electronics Engineers, 2001.
-
Abstract
- 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/sup -2/ to 10/sup 6/ Hz. The DRS analysis was backed up by dynamic mechanical and rheological experiments. In the high temperature region two loss processes (/spl alpha/ and /spl alpha/*) show up, the relaxation times of which obey the Vogel-Fulcher-Tammann (VFT) law. The dielectric /spl alpha/ process is related to the dynamic glass-rubber transition and is slightly faster than the corresponding mechanical /spl alpha/ process. A slower (high-temperature) /spl alpha/* relaxation is identified as chemical, corresponding to the mean lifetime of the hydrogen bonded linkages in the supramolecular chains. Its relaxation time /spl tau//sub /spl alpha/*/ was found to be 1 to 2 decades larger than the terminal flow relaxation time, indicating that the relaxation of an entire chain is dominated by the joint dynamics of many hydrogen bonds. The /spl beta/ relaxation, observed in both DRS and dynamic mechanical analysis (DMA) at temperatures below T/sub 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 /spl alpha/ and /spl alpha/* relaxations will be discussed in terms of temporary physical networks and cooperativity.
Details
- Language :
- English
- ISSN :
- 10709878
- Volume :
- 8
- Issue :
- 3
- Database :
- OpenAIRE
- Journal :
- IEEE Transactions on Dielectrics and Electrical Insulation
- Accession number :
- edsair.doi.dedup.....29be876b77748525a172399eb7a58d79