Conventional
cross-linked polymers cannot be reprocessed because
of the presence of permanent covalent cross-links, preventing reuse
and recycling. Covalent adaptable networks (CANs) employ dynamic covalent
bonds that undergo dynamic reactions under external stimulus, allowing
recyclability of these network materials. Hindered urea chemistry
is one of the recently discovered dissociative dynamic chemistries.
While hindered urea bonds have traditionally been exploited in the
synthesis of step-growth type CANs, the use of hindered urea bonds
in the synthesis of chain-growth-type dynamic networks has only been
narrowly explored. Here, we present a simple, catalyst-free, fast
method to synthesize a hindered-urea-based dynamic cross-linker that
can undergo a free radical polymerization with vinyl-type monomers
or polymers to form reprocessable CANs. Using this cross-linker, we
developed dynamic polymethacrylate networks that can be (re)processed
at 80 °C. These dynamic covalent networks exhibit full recovery
of cross-link density after multiple recycling steps; they are only
the second chain-growth network synthesized directly and exclusively
from carbon–carbon double bond monomers to demonstrate such
recovery. Unlike other dissociative dynamic polymer networks, polymethacrylate
networks that contain dissociative dynamic hindered urea bonds do
not flow and maintain their network structure even at high temperature
(300 °C). Despite its relatively fast reprocessability, the network
showed delayed and extremely slow stress relaxation at the processing
temperature. This work offers a simple approach to obtain reprocessable
addition-type networks based on hindered urea bonds while revealing
the limitations of stress relaxation experiments in relationship to
the processability of some dynamic polymer networks.