Chemically recyclable and room-temperature self-healable siloxane-imine benzoxazine vitrimers for soft magnetic actuation

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J. Mater. Chem. A, 2026, Advance ArticleDOI: 10.1039/D6TA02558G, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Prashansa Gupta, Bhavika Bhatia, Jan-Marten Sprenger, Adrian Wolf, Katharina Koschek, B…

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Chemically recyclable and room-temperature self-healable siloxane-imine benzoxazine vitrimers for soft magnetic actuation

* Corresponding authors

a Materials Chemistry Laboratory, Department of Chemistry, School of Natural Sciences, Shiv Nadar University, Delhi NCR, Uttar Pradesh 201314, India
E-mail: [email protected]

b Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Wiener Straße 12, 28359 Bremen, Germany
E-mail: [email protected]

c Department of Production Engineering, University of Bremen, Badgasteiner Str. 1, 28359 Bremen, Germany

d MAPEX Center for Materials and Processes, 28359 Bremen, Germany

Abstract

Designing multifunctional vitrimers that combine ambient self-healing, magnetic responsiveness, reprocessability and high thermal stability is gaining importance for sustainable soft materials. Herein, we report a siloxane-imine-bridged benzoxazine-crosslinked vitrimer prepared from a bio-based vanillin-furfurylamine benzoxazine (Vfa) and amine-functional polysiloxane, yielding a low-viscosity imine-functional prepolymer with intact benzoxazine rings. Thermal ring-opening polymerization (ROP) affords a soft vitrimer network with high thermal robustness (Tmax ∼ 550–560 °C). Stress-relaxation measurements reveal rapid exchange with an Ea of 23 kJ mol−1 and an extrapolated topology-freezing temperature (Tv) well below Tg, consistent with fast network rearrangement. Incorporation of MNPs (20 wt%) reduces the Ea to 11.4 kJ mol−1 and introduces field-addressable magneto-responsive behaviour, including reversible storage-modulus switching and shear-thinning magnetorheology. The networks show hydrophobic surfaces (water contact angle 116–130°), high creep recovery (∼93%), hydrolytic stability (≥8 days), and solvent-selective dissolution enabling recasting and reshaping. Macroscopic scratch healing occurs at room temperature within 8 h for the magnetic vitrimer while it required 24 h for the neat vitrimer, with tensile testing confirming repeatable self-healing over three cycles with average healing efficiency of 92% and 88%, respectively. Finally, reinforcement with recycled carbon-fibre felt enhances mechanical strength while preserving vitrimer-based reprocessability, enabling a sustainable circular route for soft magnetic actuators and chemically recyclable composites.