Metastability and Sol Phases: Two Keys for the Future of Molecular Gels?

Abstract

The future of molecular gels may rely on a deeper theoretical understanding of the gel-to-solid phase-separation process that usually limits the lifetime of molecular gels. Stable sol phases, when available, can be the appropriate vectors to transfer the 1D self-assembled and functional morphologies to solid substrates that may be used for technological devices.

Augmenting Photoinduced Charge Transport in a Single‐Component Gel System: Controlled In Situ Gel–Crystal Transformation at Room Temperature

“…Approximation 1 in Scheme states that if the entangled 1D wires in a 3D network exhibit a minimal contact surface overlap (CSO) between them, then the interaction in between the wires is negligible, in comparison to interaction of the components forming the 1D wire . This is of crucial importance for most stable organogels, in which a proper balance between the solvophilic and solvophobic forces renders the gel to attain a reversibly accessible local minimum, which avoids the further transformation of the system to attain a global minimum, i.e., the crystal state . The stability of wire‐like fibrils at lower concentrations of TPAPAE (c = 0.25 wt %) refers to a kinetically trapped metastable state or local minimum (Approximation 1, Scheme ) due to minimal CSO, as seen from Figure a.…”

“…[14] This is of crucial importance for most stable organogels, in whichaproper balance between the solvophilica nd solvophobic forces renders the gel to attain ar eversibly accessible local minimum, which avoids the further transformation of the system to attain ag lobal minimum, i.e.,t he crystal state. [33][34][35][36] The stabilityo fw ire-like fibrils at lower concentrations of TPAPAE (c = 0.25 wt %) referst oak inetically trapped metastable state or local minimum (Approximation 1, Scheme 2) due to minimal CSO, as seen from Figure 5a.T he metastable state refers to an equilibrium state of the molecular aggregation and the solubilizingg elator-solvent interactions. The kinetic barriers for the negligibly interacting self-assembled molecular nanowires at this stage are extremelyh igh to overcomet he transition state to attain the globalm inimum.…”

A molecular insight into the nature of crystallographic mismatches in self-assembled fibrillar networks under non-isothermal crystallization conditions

“…Fundamental research on molecular gels, capable of self-assembling into fibrillar networks, has primarily focused on structural and mechanical characterization of these soft materials. 1 This, in part, is due to the numerous, assorted applications of these complex systems including: drug delivery, 2,3 tissue engineering, 4 lipid structuring [5][6][7] and scaffolding systems. 8 To illustrate the structural significance of these materials in practical applications, such as drug delivery, the rate of release is a function of the bioseparation process.…”

Supramolecular Fibers in Gels Can Be at Thermodynamic Equilibrium: A Simple Packing Model Reveals Preferential Fibril Formation versus Crystallization

“…For the thermodynamic nature of the gel state, two different scenarios have been proposed. In the first scenario, the gel state (GS) is a kinetically trapped metastable state, which avoids the transformation of the system to the crystals state (CS). ,− The main argument supporting this is that a 3D extended structure (CS) allows a higher number of stabilizing interactions than a 1D structure (GS). Depending on the depth of the metastable state and the activation barriers around it, the system could transition to the CS, and this gel–crystal transition has been observed for several systems. ,,− …”

“…The concept of thermodynamically favored formation of 1D nanostructures has been successfully applied in molecular dynamic simulations and in studies of gels to develop tools to investigate the gelation tendencies as a function of the free energy. , Furthermore, self-healing gels depend on the possibility of gels to represent the thermodynamic equilibrium (although it could be argued that a local minimum could also represent a gel state that can be reversible accessed). It has been argued that “thermodynamically stable gels” represent deep local minima surrounded by high activation barriers which may make it impossible to access the global minimum, the CS. ,,− …”