Rheologica Acta, Vol.46, No.5, 755-764, 2007
Amorphous and crystalline states of ultrasoft colloids: a molecular dynamics study
In this work, we study the temperature-induced development of "dynamically arrested" states in dense suspensions of "soft colloids" (multi-arm star polymers and/or block-copolymers micelles) by means of molecular dynamics ( MD) simulations. Temperature increase in marginal solvents results in "soft sphere" swelling, dynamical arrest, and eventually crystallization. However, two distinct "dynamically arrested" states were found, one almost amorphous ("glassy") and one with a considerable degree of crystallinity, yet lower than that of the fully equilibrated crystal. It is remarkable that even that latter state permitted self-diffusion in the timescale of the simulations, an effect that underlies the importance of the "ultra- soft" nature of inter-particle potential. The "number of connections" criterion for crystallinity proved to be very successful in identifying the ultimate thermodynamic trend from the very early stages of the alpha- relaxation.