Molecular Characterization of Polymer Networks

Abstract

Polymer networks are complex systems consisting of molecular components. Whereas the properties of the individual components are typically well understood by most chemists, translating that chemical insight into polymer networks themselves is limited by the statistical and poorly defined nature of network structures. As a result, it is challenging, if not currently impossible, to extrapolate from the molecular behavior of components to the full range of performance and properties of the entire polymer network. Polymer networks therefore present an unrealized, important, and interdisciplinary opportunity to exert molecular-level, chemical control on material macroscopic properties. A barrier to sophisticated molecular approaches to polymer networks is that the techniques for characterizing the molecular structure of networks are often unfamiliar to many scientists. Here, we present a critical overview of the current characterization techniques available to understand the relation between the molecular properties and the resulting performance and behavior of polymer networks, in the absence of added fillers. We highlight the methods available to characterize the chemistry and molecular-level properties of individual polymer strands and junctions, the gelation process by which strands form networks, the structure of the resulting network, and the dynamics and mechanics of the final material. The purpose is not to serve as a detailed manual for conducting these measurements but rather to unify the underlying principles, point out remaining challenges, and provide a concise overview by which chemists can plan characterization strategies that suit their research objectives. Because polymer networks cannot often be sufficiently characterized with a single method, strategic combinations of multiple techniques are typically required for their molecular characterization.

Intermediate structural hierarchy in biological networks modulates the fractal dimension and force distribution of percolating clusters

“…We begin with an investigation of the cross-link coordination per monomer and the network fractal dimension. These structural properties have been analysed in the context of many biological networks[50, 51], and identified as useful in the characterisation of polymeric networks[52]. We previously calculated these values in monomeric pseudo-colloidal networks[32] where both were shown to affect the pore size distribution and mechanical response of those networks.…”

Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study

“…The macroscopic properties of rubbers required for industrial applications are strongly related to the complex structure of the three-dimensional network of crosslinks formed during vulcanization [17][18][19][20][21][22]. This structure is defined by the number and spatial distribution of crosslinks and by their functionality and chemical nature, as well as by the presence of defects (pendant chains, loops, and chain modifications) and entanglements.…”

Suppressing Creep and Promoting Fast Reprocessing of Vitrimers with Reversibly Trapped Amines

“…For this purpose, several strategies have been applied with the main focus on phase separation, [21–23] cross‐linking density, [4, 24–28] and the combination of permanent and transient bonds in order to hinder low temperature material deformation [29–33] . However, from a more general material design point of view, [34] a (theoretically) defect‐free vitrimer should show only elastic behaviour upon deformation [35] . Especially when considering that for most known vitrimer chemistries, it was experimentally demonstrated that viscous flow relies on the presence of reactive chain ends or side chains.…”