Activation Energy for Dissociation of Hydrogen‐Bonding Crosslinkers in Phase‐Change Salogels: Dynamic Light Scattering versus Rheological Studies

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 (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 higher T-gel. Both stress relaxation and DLS data can be fitted by the exponential functions with temperature-independent exponents of approximate to 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 approximate to 130-140 kJ mol(-1) for salogels with both linear and dendritic crosslinkers.