Dissociation energy of dynamic bonds in thermoresponsive phase‐change salogels is explored using rheology and dynamic light scattering (DLS). The salogels are formed by polyvinyl alcohol (PVA) reversibly crosslinked by hydrogen‐bonding amine‐terminated molecules in an inorganic phase‐change material—lithium nitrate trihydrate (LNH) salt—as a solvent. The crosslinker geometry (linear vs branched) has a strong effect on both the gelation temperature (
Hierarchy of relaxation times in supramolecular polymer model networks
Supramolecular polymer gels are an evolving class of soft materials with a vast number of properties that can be tuned to desired applications. Despite continuous advances concerning polymer synthesis, sustainability or adaptability, a consistent understanding of the interplay between structure, dynamics, and diffusion processes within transient networks is lacking. In this study, the hierarchy of several relaxation processes is investigated, starting from a microscopic perspective of a single sticker dissociation event up to the center-of-mass diffusion of a star-shaped polymer building block on different length scales, as well as the resulting macroscopic mechanical response to applied external stress. In addition to that, a second focus is placed on the gel micro-structure that is analyzed by light scattering. Conversion of the dynamic light scattering (DLS) inverse length scale into real space allows for a combination of relaxation times with those obtained by forced Rayleigh scattering (FRS). For these investigations, a model-type metallo-supramolecular network consisting of narrowly dispersed tetra-arm poly(ethylene glycol)-terpyridine macromolecules that are interconnected via complexation with zinc ions is chosen. Assembling the obtained activation energies reveals that all complex dissociation-governed relaxation processes exhibit similar activation energies.
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- Award ID(s):
- 1709315
- NSF-PAR ID:
- 10454161
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 24
- Issue:
- 8
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 4859 to 4870
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract T gel) and the crosslinker to polymer ratio at which the gelation occurs. Due to their higher functionality, dendritic crosslinkers are more efficient gelators as compared to their linear counterparts, inducing PVA gelation at a lower concentration of a crosslinker and resulting in salogels with higherT gel. Both stress relaxation and DLS data can be fitted by the exponential functions with temperature‐independent exponents of ≈0.5 and 2, respectively. For the first time, it is reported that the crosslinker dissociation activation energy determined from the rheological stress relaxation time and DLS slow mode decay time are in very good agreement, comprising ≈130–140 kJ mol−1for salogels with both linear and dendritic crosslinkers. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1CP04213K
