Dynamic hindered urea chemistry has been extensively used in the synthesis of reprocessable polyurea and poly(urethane-urea) networks where the content of hindered urea bonds is very high (&gt;50 mol%). In this work, we demonstrate that the dynamic nature of hindered urea bonds can be further exploited in the synthesis of reprocessable addition-type polymer networks made from vinyl-type monomers or polymers. We designed a simple, fast, and catalyst-free method to synthesize a hindered-urea-based dynamic cross-linker that can undergo a free radical polymerization. By incorporating only 5 mol% of this cross-linker, we were able to produce polymethacrylate networks that can be (re)processed multiple times with full recovery of cross-link density after recycling. Despite of their dissociative nature, the synthesized networks do not flow and maintain their cross-linked nature at very high temperature (300 °C). Notably, while the HUB-based polymethacrylate network can be processed at relatively mild temperatures (40-80 °C), the network shows delayed and extremely slow stress relaxation at the processing temperature, revealing the importance of pressure or compressive stress on the processability of this HUB dynamic polymer network.

Reprocessable addition-type polymer networks based on dynamic hindered urea bonds with full recovery of cross-link density after recycling

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