Macromolecular Metamorphosis in a Polymer Network via the Reversible Collapse of Single-Chain Nanoparticles

The macromolecular architecture of strands and cross-links in a polymer network plays an indispensable role in determining its properties, such as elasticity, network dynamics, and degree of defect tolerance. However, the fixed topology of traditional networks limits their performance to a single configuration. Herein, a novel topology-switching polymer network that incorporates single-chain nanoparticles (SCNPs) as cross-links (PSNN) is proposed. Experimental and theoretical studies via microrheology and small-angle X-ray scattering analyses were used to study the relationship between the microstructure of polymer networks (i.e., mesh size, terminal relaxation time, and fluctuation behavior among cross-links) and their properties. PSNNs exhibit superior properties, including improved stiffness, strength, thermal stability, and dielectric strength, to conventional polymer networks. Additionally, the heat-induced reversible metamorphosis of SCNPs allows reversible alteration of the network properties of PSNNs. This technique has the potential to create multifunctional polymer networks with tailored properties that can be widely used in intelligent responsive engineering, soft robotics, photo actuators, energy storage, and dielectric elastomers.