Activation Energy for Dissociation of Hydrogen‐Bonding Crosslinkers in Phase‐Change Salogels: Dynamic Light Scattering versus Rheological Studies. Issue 22 (21st October 2019)

• Record Type: Journal Article
• Authors: Karimineghlani, Parvin; Sukhishvili, Svetlana A.
• Is Part Of: Macromolecular chemistry and physics. Volume 220:Issue 22(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-10-21
• Subjects: activation energy -- dynamic light scattering -- phase‐change salogels -- rheology -- temperature‐responsive gels; Polymers -- Periodicals; Polymerization -- Periodicals; Synthetic products -- Periodicals; Macromolecules -- Periodicals; 547.7
• DOI: 10.1002/macp.201900329
• Languages: English
• ISSNs: 1022-1352

Abstract

Abstract: 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. Abstract : For phase‐change salogels, a higher affinity for branched crosslinkers in comparison to linear ones for hydrogen bonding with polymer chains is reported. Moreover, good agreement for the network dissociation apparent activation energy determined by dynamic light scattering (DLS) and rheology is demonstrated.