Crosslinker mobility weakens transient polymer networks

Abstract

Transient networks comprised of polymers connected by short-lived bonds are a common design theme for both biological and synthetic materials. Transient bonds can provide mechanical rigidity, while still allowing for visco-elastic flows on timescales longer than the bond lifetime. In many biological polymer networks such as the actin cytoskeleton, the short-lived bonds are formed by accessory proteins that diffuse away after unbinding. By contrast, bonds in synthetic networks, such as the pendant groups of telechelic polymers, can only rebind in the same location. Using a recently developed theoretical model of the fracturing of visco-elastic materials, we here investigate the effect of linker mobility on the bond dynamics of a network under stress. We find that although mean field properties such as the average bond linker lifetime are barely affected by bond mobility, networks cross linked by mobile bonds fracture more readily due to 'leaking' of linkers from crack areas to less stressed regions within the network. We propose a theoretical model to describe the redistribution of mobile linkers, which we validate by simulations. Our work offers insight into a potential trade-off that cells face, between fracture strength versus the modularity and tight dynamic control offered by mobile linkers. arXiv:1805.12431v1 [cond-mat.soft]

Surface Tension Controls the Hydraulic Fracture of Adhesive Interfaces Bridged by Molecular Bonds

“…To explain the higher probability of failure at high D, we reasoned that crack growth by biased diffusion of marginal bonds can extend the crack beyond a critical length at which bond breaking dominates rebinding. Thus, our model suggests that mobility of bonds embrittles the adhesive interface, in interesting analogy with the weakening of transient polymer networks by crosslinker mobility [33]. According to this mechanism of embrittlement by bond motion, the progressive immobilization of cadherins as they couple to the cortex observed during maturation of cell-cell junctions should promote stability of the adhesion patch [34].…”

Frustrated binding of biopolymer crosslinkers

“…We attribute this dierence to the large bending rigidity of the actin laments, which frustrates doubly bound crosslinkers. Our new kinetic data allow for more precise computational modeling of actin networks [21,26], and give insight into the dynamics of the cell cortex [1,27]. Lastly, we expect that our work will help to design synthetic materials with programmed timescales of relaxation [14,28].…”

Energy‐Dissipating Polymeric Silicone Surfactants

“…[ 4 ] Transient polymer networks (TPNs) represent an alternative to traditional STFs because they do not require the addition of particles or a secondary phase. They are comprised of supramolecular polymer chains that reversibly connect via short‐lived crosslinks that allow the polymer to flow while maintaining a certain mechanical integrity; [ 5 ] TPNs can act elastically under fast deformation but start to flow after the removal of the force. Dynamic crosslinks include noncovalent interactions such as metal‐ligand coordination, [ 6 ] hydrophobic interactions, [ 7 ] π–π stacking, [6a, 8] or hydrogen bonding.…”