Planar nucleation and oriented growth of (002) crystal plane is visualized by in situ electrochemical atomic force microscopy on an Ag-modified surface. The high solubility of Ag in Zn metal enables formation of solid solution buffer layer with g...
Artikel
Carbodiimide‐Driven Toughening of Interpenetrated Polymer Networks
Von Wiley-VCH zur Verfügung gestellt
Responsive networks are synthesized with distinct polymer arrangements of the polymers. The structure of the network impacts the materials properties in both the resting state, and in the presence of carbodiimide fuels which transiently form anhydride crosslinks. Interpenetrated materials in the fueled state have superior fracture and compressive properties.
Abstract
Recent work has demonstrated that temporary crosslinks in polymer networks generated by chemical “fuels” afford materials with large, transient changes in their mechanical properties. This can be accomplished in carboxylic-acid-functionalized polymer hydrogels using carbodiimides, which generate anhydride crosslinks with lifetimes on the order of minutes to hours. Here, the impact of the polymer network architecture on the mechanical properties of transiently crosslinked materials was explored. Single networks (SNs) were compared to interpenetrated networks (IPNs). Notably, semi-IPN precursors that give IPNs on treatment with carbodiimide give much higher fracture energies (i.e., resistance to fracture) and superior resistance to compressive strain compared to other network architectures. A precursor semi-IPN material featuring acrylic acid in only the free polymer chains yields, on treatment with carbodiimide, an IPN with a fracture energy of 2400 J/m2, a fourfold increase compared to an analogous semi-IPN precursor that yields a SN. This resistance to fracture enables the formation of macroscopic complex cut patterns, even at high strain, underscoring the pivotal role of polymer architecture in mechanical performance.
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