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1. Isodesmic Supramolecular Assembly of Phenylethynylene Bis‐Urea Macrocycles

   https://doi.org/10.1002/chem.71183  

   Gbadamosi, Fahidat A; Zubaer, Kazi Md; Samant, Vaibhavi A; Eubanks, Jillian; Garashchuk, Sophya; Shimizu, Linda S (May 2026, Chemistry – A European Journal)

   ABSTRACT In this study, we report a soluble phenylethynylene bis‐urea macrocycle with a supramolecular assembly mechanism distinct from previously studied bis‐urea macrocycles. The macrocycle was synthesized via a dynamic covalent synthesis approach with two exteriorn‐dodecyloxy groups to enhance solubility in organic and mixed aqueous media. Temperature‐dependent UV‐Visible and fluorescence spectroscopy in 45% H₂O/THF are well described by an isodesmic mechanism, characterized by a clear isosbestic point, strong enthalpic stabilization (ΔH ∼ ‐133 kJ mol⁻¹), and a degree of polymerization of ∼4 at 284 K. Fourier‐transform infrared (FTIR) spectroscopy confirms hydrogen‐bond‐driven association. Matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) detects primarily dimers, likely due to dissociation during ionization. Dynamic light scattering (DLS) and atomic force microscopy (AFM) showed the formation of nanoscale aggregates and fibrillar supramolecular structures. Additives capable of engaging the urea NH units, including a phosphate‐functionalized quarterphenyl guest, reduced both the enthalpy and degree of polymerization, demonstrating tunable control of chain length. Overall, these findings identify this phenylethynylene bis‐urea macrocycle as a rare example of an isodesmic, hydrogen‐bonded supramolecular polymer in polar media and highlight design principles for controlling assembly length and developing solution‐phase host‐guest frameworks. 

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2. Polymer architecture dictates multiple relaxation processes in soft networks with two orthogonal dynamic bonds

   https://doi.org/10.1038/s41467-023-43073-w  

   Ge, Sirui; Tsao, Yu-Hsuan; Evans, Christopher M (December 2023, Nature Communications)

   Abstract Materials with tunable modulus, viscosity, and complex viscoelastic spectra are crucial in applications such as self-healing, additive manufacturing, and energy damping. It is still challenging to predictively design polymer networks with hierarchical relaxation processes, as many competing factors affect dynamics. Here, networks with both pendant and telechelic architecture are synthesized with mixed orthogonal dynamic bonds to understand how the network connectivity and bond exchange mechanisms govern the overall relaxation spectrum. A hydrogen-bonding group and a vitrimeric dynamic crosslinker are combined into the same network, and multimodal relaxation is observed in both pendant and telechelic networks. This is in stark contrast to similar networks where two dynamic bonds share the same exchange mechanism. With the incorporation of orthogonal dynamic bonds, the mixed network also demonstrates excellent damping and improved mechanical properties. In addition, two relaxation processes arise when only hydrogen-bond exchange is present, and both modes are retained in the mixed dynamic networks. This work provides molecular insights for the predictive design of hierarchical dynamics in soft materials. 

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3. Vitrimer Nanocomposites from Polymerization‐Induced Self‐Assembly

   https://doi.org/10.1002/adma.202512303  

   Le, Thi H; Stewart, Kevin A; Eades, Cabell B; Bowman, Jared I; Wei, Nathan B; Sumerlin, Brent S (January 2026, Advanced Materials)

   Abstract Vitrimers, a class of covalent adaptable networks (CANs), promise sustainability through recyclability and reprocessability, yet suffer from creep under prolonged stress due to dynamic bond exchange. Here, a materials design strategy is reported that integrates polymerization‐induced self‐assembly (PISA) to embed core‐crosslinked nanoparticles within vitrimer networks, yielding hierarchical dual‐crosslinked systems with a reduction of creep susceptibility by up to 90% at 150 °C yet good reprocessability at elevated temperatures (E_a= 246 kJ mol⁻¹). These spherical nanostructures restrict chain mobility and act as rheological modifiers that can be synthetically tuned through core block length. This approach offers precise architectural control, leveraging nanoparticle phase morphology to direct bulk vitrimer properties. This study establishes a new paradigm for creep‐resistant CANs and showcases how PISA can advance vitrimer performance by structurally encoding mechanical robustness and reprocessability. 

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4. Lignin-derivable, thermally healable thiol-acrylate vitrimers with improved mechanical performance and reprocessability via transesterification

   https://doi.org/10.1039/D5SU00182J  

   Wong, Yu-Tai; Mahajan, Jignesh S; Synnott, Stephanie; Korley, LaShanda_T J (August 2025, RSC Sustainability)

   The development of vitrimers with dynamic covalent bonds enables reprocessability in crosslinked networks, offering a sustainable alternative to conventional thermosets. In this work, a thiol-acrylate vitrimer was synthesized from lignin-derivable (bis)phenols (guaiacol and bisguaiacol F) and compared to a control derived from petroleum-based precursors (phenol and bisphenol F) to investigate the effect of structural differences on network properties and thermal reprocessing. The presence of methoxy groups in the lignin-derivable vitrimer promoted intermolecular interactions by serving as additional hydrogen bonding acceptors during curing, leading to a denser network, as evidenced by a higher rubbery storage modulus (∼2.4 MPa vs. ∼1.4 MPa) and glass transition temperature (∼34 °C vs. ∼28 °C). The lignin-derivable vitrimer exhibited a slightly higher elongation-at-break (∼170% vs. ∼130%) and improved mechanical robustness, including a nearly two-fold increase in Young's modulus (∼6.9 MPa vs. ∼3.4 MPa) and toughness (∼750 kJ m−3vs. ∼390 kJ m−3). The similar stress relaxation behavior and activation energy of viscous flow indicated comparable bond exchange dynamics between the two vitrimers, while the lignin-derivable system demonstrated higher thermal healing efficiency with improved recovery of tensile properties after reprocessing. These findings highlight the potential of lignin-based aromatics in designing mechanically robust and sustainable vitrimers, aligning with efforts to develop renewable and reprocessable polymeric materials. 

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5. Impact of dynamic covalent chemistry and precise linker length on crystallization kinetics and morphology in ethylene vitrimers

   https://doi.org/10.1039/D1SM01288F  

   Soman, Bhaskar; Go, Yoo Kyung; Shen, Chengtian; Leal, Cecilia; Evans, Christopher M. (January 2022, Soft Matter)

   Vitrimers, dynamic polymer networks with topology conserving exchange reactions, have emerged as a promising platform for sustainable and reprocessable materials. While prior work has documented how dynamic bonds impact stress relaxation and viscosity, their role on crystallization has not been systematically explored. Precise ethylene vitrimers with 8, 10, or 12 methylene units between boronic ester junctions were investigated to understand the impact of bond exchange on crystallization kinetics and morphology. Compared to linear polyethylene which has been heavily investigated for decades, a long induction period for crystallization is seen in the vitrimers ultimately taking weeks in the densest networks. An increase in melting temperatures ( T m ) of 25–30 K is observed with isothermal crystallization over 30 days. Both C 10 and C 12 networks initially form hexagonal crystals, while the C 10 network transforms to orthorhombic over the 30 day window as observed with wide angle X-ray scattering (WAXS) and optical microscopy (OM). After 150 days of isothermal crystallization, the three linker lengths led to double diamond (C 8 ), orthorhombic (C 10 ), and hexagonal (C 12 ) crystals indicating the importance of precision on final morphology. Control experiments on a precise, permanent network implicate dynamic bonds as the cause of long-time rearrangements of the crystals, which is critical to understand for applications of semi-crystalline vitrimers. The dynamic bonds also allow the networks to dissolve in water and alcohol-based solvents to monomers, followed by repolymerization while preserving the mechanical properties and melting temperatures. 

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