Synthesis of poly(acetoacetoxyethyl methacrylate-b-dimethylsiloxane-b-acetoacetoxyethyl methacrylate) triblock copolymers via SARA ATRP for reaction-mediated microphase separation of sustainable vitrimers

Abstract Vitrimers offer a sustainable route to covalently crosslinked polymer networks with processability enabled by thermally activated bond-exchange reactions. However, the integration of programmable nanostructures into vitrimer networks remains challenging because of the competition between phase behavior and the curing process. Here, we report an environmentally conscious synthesis of ABA-type triblock copolymers (tBCPs), poly(acetoacetoxyethyl methacrylate- b -dimethylsiloxane- b -acetoacetoxyethyl methacrylate) (P(AAEMA- b -DMS- b -AAEMA)), using a supplemental activator and reducing agent (SARA) atom transfer radical polymerization (ATRP) technique. In this approach, a Br–poly(dimethylsiloxane)–Br (Br–PDMS–Br) macroinitiator and a low-concentration (ppm-level) CuBr 2 catalyst were used. The resulting high-χ tBCPs exhibited facile composition-dependent bulk morphologies spanning spheres, cylinders, and lamellae on a scale of approximately 30 nm, as confirmed by small-angle X-ray scattering (SAXS). Subsequently, vinylogous urethane vitrimer networks were prepared by crosslinking the β-ketoester (β-KE) units with hexamethylenediamine (HMDA) at 80 °C, followed by postcuring via hot-pressing at 160 °C. Compared with the tBCP precursor, vitrimerization markedly enhances the thermal resistance, thereby increasing the 5% weight-loss temperature ( T d,5% ) by 51 °C. The results of SAXS analysis before and after vitrimer formation revealed that curing/processing largely suppresses higher-order reflections and yields broadened primary maxima, indicating the formation of less long-range order and primarily nonordered microphase-separated structures. Mediating the NH 2 /β-KE ratio (1 vs. 2) induces modest but systematic changes in the peak position and width, suggesting that the crosslink density affects segregation/coherence, while the reaction-mediated microphase separation (REMPS) pathway during curing governs primarily the loss of tBCP-derived lattice order. This study presents a scalable ATRP-to-vitrimer strategy for preparing PDMS-containing nanostructured networks and provides mechanistic insight into morphology evolution during vitrimerization.