Relaxation and Dynamics in Transient Polymer Model Networks

Abstract

Supramolecular polymer networks have promising potential to serve as self-healing soft materials. To benefit from this ability, quantitative understanding of the underlying mechanisms of macromolecular dynamics and transient association must be achieved. A key to obtaining such understanding is to understand the dynamics and relaxation of supramolecular polymer networks, which is often complexed by inhomogeneous polymer-network structures. To overcome this limitation, we use a set of regular star-shaped poly(ethylene glycol) polymers end-capped with terpyridine groups that can transiently coordinate to different metal ions, thereby forming transient supramolecular polymer networks with determined homogeneous architectures and determined binding strength. We study these networks in view of their mechanics, dynamics, and relaxation from both macroscopic and microscopic perspectives through the use of rheology, dynamic light scattering, and fluorescence recovery after photobleaching. These studies reveal that whereas in a long-term average the networks exhibit percolated connectivity, temporal detachment of one of the arms of the star-polymer building blocks allows for their relocation within the networks, entailing relaxation and flow on long time scales.

Controlling the melt rheology of linear entangled metallo-supramolecular polymers

“…This last number depends on the initial number of monomers N 0 , being equal to N 0 (1-p a ). Knowing that x is equal to ratio between M(x), the molar mass of the chain of degree of polymerization x and M 0 , the mass of one monomer, the weight fraction of chains of mass M, w(M), is defined as: (2) Assuming that the MMD of the linear assemblies are well represented by a Flory distribution, the number of unknown parameters to define their MMD is reduced to only one parameter, the weight average molar mass of the sample, M w (with M n =M w /2=M 0 /(1-p a )). The dispersity of such distributions is, by definition, fixed to 2.…”

The impact of damage accumulation on the kinetics of network strength recovery for a physical polymer gel subjected to shear deformation

“…16 Several methods for characterizing the fracture-healing behavior of viscoelastic gels have been proposed in literature using shear rheological experiments. 13,[17][18][19][20] These methods typically use oscillation-based measurements to evaluate postdeformation strength recovery and are similar to the tests used to measure network gelation kinetics. 21,22 For "shear thinning" injectable materials, the material's storage modulus (G 0 ) is the critical parameter used to quantify selfhealing behavior because it describes the elastic character of Additional Supporting Information may be found in the online version of this article.…”

“…25 This "shear-rest-shear" measurement protocol is different from the oscillatory techniques used by others, 13,[17][18][19][20] in which the gel was always exposed to some small amount of deformation during the period of recovery. The applied shear rate (1 s 21 ) is also much lower than those used to shear thin materials discussed previously for the oscillation time sweeps.…”

Modulation of Assembly and Dynamics in Colloidal Hydrogels via Ionic Bridge from Cellulose Nanofibrils and Poly(ethylene glycol)

“…11 Understanding the role of dynamics and structure mechanisms in an associative polymeric gel is critical for designing soft materials. 12,13 Whereas the preparation of most supramolecular hydrogels generally relies on cyclic heating/cooling process, in situ polymerization, or cross-linking reaction, the idea of achievement of dynamic hydrogels by mixing the components in aqueous solution at room temperature is highly desirable. 14,15 Natural materials provide prototypes for outstanding mechanical properties using recyclable materials, and cellulose is a typical example that involves subtle combination of assemblies with hierarchical structure.…”