Effect of Junction Aggregation on the Dynamics of Supramolecular Polymers and Networks

Abstract

Transient structures based on associative polymers can deliver complex functions; as such, they hold promise for advanced applications as in drug delivery, tissue engineering, and electronics. The network structure and timescale of its rearrangement are key factors that define their range of utility. However, the inevitable phase separation of polar pairwise associations from nonpolar polymer chains frequently causes junction aggregation, whose stability and functionality significantly affect the network structure and dynamics, and as such, redefine its utility. Engineering the extent of association is a necessity for controlling properties of supramolecular materials, yet the current knowledge of the effect of design parameters on specificities of aggregates and their consequent effects on material properties is limited. To address this gap, the importance of aggregation is highlighted, the available theories and models of the dynamics of associative polymers in the presence of aggregates are reviewed, and the existing experimental records to draw a general guideline for interpreting the effect of aggregates on polymer dynamics are classified. Moreover, pitfalls and considerations like the applicability of time-temperature superposition, and the interplay of kinetics and thermodynamics of aggregation that may undermine the authenticity of the reported data are reviewed.

Self-organization of metallo-supramolecular polymer networks by free formation of pyridine–phenanthroline heteroleptic complexes

“…Other explanations like the extensive formation of mono complexes 56 and their aggregation 57 can be ruled out considering the trend in modulus and the narrow terminal relaxation observed at largest concentration of metal ions, which should have been broadened in the presence of aggregates. 58,59 Moreover, a dual relaxation process becomes evident at higher Lig : M ratios or lower metal ion concentrations, which suggests the coexistence of at least two coordination geometries for EPhen–Pd 2+ complexes. The faster relaxation mode, whose characteristic time and intensity monotonically decrease with Lig : M ratio (gets weaker and shifts to higher frequencies), appears at the measurable frequency window, while the slower mode is always below the accessible frequency range.…”

Coordination Geometry and Mineralization in Self-Healing Mussel-Inspired Hydrogels

“…The relaxation is likely through the effective breakup of the network strands, which are more uniform in tris complex governing conditions. The emergence of the low-frequency relaxation mode has been frequently reported in many supramolecular polymer networks, specifically in side-chain systems at bulk conditions. , This is commonly associated with the phase-separation of the supramolecular associations due to the polarity difference with the polymer backbone, ,, or following the nucleation and growth of ordered structures initiated by secondary interactions between binary associations . In iron-based mussel-inspired systems, however, the mineralization of metal ions and the in situ formation of ion aggregates at network junctions have been reported. ,, The catechol groups are claimed to form transient bonds with the surface of Fe 3 O 4 nanoparticles, even at neutral pH values, since even the formation monocomplexes is enough to form network junctions with nanoparticles .…”

“…The emergence of the low-frequency relaxation mode has been frequently reported in many supramolecular polymer networks, specifically in side-chain systems at bulk conditions. 70,71 This is commonly associated with the phase-separation of the supramolecular associations due to the polarity difference with the polymer backbone, 13,54,71 or following the nucleation and growth of ordered structures initiated by secondary interactions between binary associations. 72 In iron-based mussel-inspired systems, however, the mineralization of metal ions and the in situ formation of ion aggregates at network junctions have been reported.…”

Constraining effects on polymer chain relaxation in crosslinked supramolecular dual networks

“…To determine the activation energy of the TN, it is necessary to consider the motion of the connected segments and to correct the attempt time for bond dissociation by the segment relaxation time. The following equation is used to estimate the activation energy (Zhang et al, 2017;Ge et al, 2020;Ahmadi et al, 2023):…”