Multi-Cyclic Swelling for Self-Regulated Growth of Covalently Crosslinked Polymers

Organisms are capable of self-growth through the integration of the nutrients provided by the external environment. This process slows down when they grow. In this study, we mimicked this self-regulated growth via a simple swelling-polymerization strategy in which the stretching polymer chains in the original networks provide entropic elasticity to restrict growth in high growth cycles. Using typical covalently crosslinked polymers, such as acrylamide-based hydrogels and HBA-based elastomers, as examples, we demonstrate that the crosslinked polymers can absorb polymerizable compounds through a swelling-polymerization process to expand their sizes, but the growth extent becomes smaller with increasing growth cycle until reaching a plateau. In addition to their size, these materials become stiffer and exhibit less swelling ability in solvents. Our work not only provides a new growing mode to tune the properties of crosslinked polymers but also discloses the underlying mechanism of crosslinked polymers in multi-cyclic swelling conditions.