We report a numerical study, covering a wide range of packing fraction $\varphi$ and temperature $T$, for a system of particles interacting via a square well potential supplemented by an additional constraint on the maximum number $n_{\max }$ of bonded interactions. We show that, when $n_{\max }<6$, the liquid-gas coexistence region shrinks, giving access to regions of low $\varphi$ where dynamics can be followed down to low $T$ without an intervening phase separation. We characterize these arrested states at low densities (gel states) in terms of structure and dynamical slowing down, pointing out features which are very different from the standard glassy states observed at high $\varphi$ values.

This review summarizes the opportunities offered by internal and external confinement of single-chain nanoparticles (SCNPs) in catalysts, drug delivery, sensing, and other emerging potential applications.

We use theory and simulations to investigate the existence of amorphous glassy states in ultrasoft colloids. We combine the hypernetted chain approximation with mode-coupling theory to study the dynamic phase diagram of soft repulsive spheres interacting with a Hertzian potential, focusing on low temperatures and large densities. At constant temperature, we find that an amorphous glassy state is entered upon compression, as in colloidal hard spheres, but the glass unexpectedly melts when density increases further. We attribute this reentrant fluid-glass transition to particle softness and correlate this behavior to previously reported anomalies in soft systems, thus emphasizing its generality. The predicted fluid-glass-fluid sequence is confirmed numerically.