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Activation Energy for Dissociation of Hydrogen‐Bonding Crosslinkers in Phase‐Change Salogels: Dynamic Light Scattering versus Rheological Studies
Author(s) -
Karimineghlani Parvin,
Sukhishvili Svetlana A.
Publication year - 2019
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201900329
Subject(s) - dynamic light scattering , activation energy , dissociation (chemistry) , polymer chemistry , rheology , hydrogen bond , chemistry , solvent , polymer , molecule , chemical engineering , materials science , organic chemistry , nanoparticle , nanotechnology , composite material , engineering
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 ≈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 −1 for salogels with both linear and dendritic crosslinkers.