Photorheology and Gelation during Polymerization of Coordinated Ionic Liquids

Abstract

Ionic liquids (ILs) containing reactive groups provide a tunable medium for bulk polymerization and network formation with potential applications as 3D-printable materials. In this study, dynamic rheology and real-time Fourier transform infrared spectroscopy are used to monitor the in situ photopolymerization and gelation of coordinated ILs containing varying molar ratios of 1-vinylimidazole (Vim) to lithium bistriflimide (LiTf2N). Three distinct regimes are observed: (1) at low [LiTf2N], samples increase in complex shear modulus (G*) and conversion faster with increasing [LiTf2N] and behave as solutions; (2) at intermediate [LiTf2N], G* growth and conversion achieve local maxima, and samples undergo sol-to-gel transitions during polymerization; (3) at high [LiTf2N], G* growth and conversion slow with [LiTf2N], and samples exhibit viscoelastic material behavior. Gelation is attributed to Li+ coordination with imidazole pendant groups to form physical cross-links between polymer chains, while the three regimes reflect the interplay of competing effects of increased polymer content and coordination-induced cross-linking. Rheological dark curing is also observed at high [LiTf2N] due to continued physical cross-linking by Li+ after cessation of UV light.

Glassy Metal–Organic‐Framework‐Based Quasi‐Solid‐State Electrolyte for High‐Performance Lithium‐Metal Batteries

“…This means that the ion conduction in LGZ has another pattern apart from the surface form. The previous studies validated that N species in imidazole groups can interact with Li + via weak electrostatic force, [ 26a,30 ] regulate Li + flux, [ 31 ] and promote Li + conduction. [ 26a,31 ] In addition, glassy materials can afford the isotropic pathway with reduced impedance for ions’ transfer.…”

Hot Lithography Vat Photopolymerisation 3D Printing: Vat Temperature vs. Mixture Design

“…Higher conversions during the printing process benefits dimensional stability of the parts in two ways: (1) Higher T g and modulus was achieved, therefore the parts were stiffer and more resistant to dimensional change after printing; (2) achieving higher conversions during the printing process reduces the “dark polymerisation” after printing and causes less polymerisation while ageing, therefore improving the dimensional stability of the parts. Dark polymerisation is defined as the continued polymerisation after the light source is removed [ 29 ]. Once again, Mixture A showed more dependency on the heat, and the impact of the process temperature on the stability of the parts was more pronounced compared to Mixture B.…”

High-Axial-Aspect Tannic Acid Microparticles Facilitate Gelation and Injectability of Collagen-Based Hydrogels

“…To understand the sol–gel transition in more detail, we conducted time sweep experiments with samples having different weight ratios of dissolved TA and TA particles. Samples originally at 4 °C were placed in a rheometer at 37 °C, and their G ′ and G ″ were monitored as a function of time Figure f shows the evolution of G ′ and G ″ for collagen alone (Col-only), collagen with TA particles (Col-0.05-pTA), and collagen with dissolved TA (Col-0.05-sTA) over time.…”

“…Samples originally at 4 °C were placed in a rheometer at 37 °C, and their G′ and G″ were monitored as a function of time. 55 Figure 3f shows the evolution of G′ and G″ for collagen alone (Col-only), collagen with TA particles (Col-0.05-pTA), and collagen with dissolved TA (Col-0.05-sTA) over time. We see a slight dip in both moduli initially due to the rapid increase in temperature, from 4 to 37 °C (temperature ramp shown in red in Figure 3f).…”