Absence of the rotator phase and evolution of dynamical motions in cluster monolayers

TLDR: In this article, the quasielastic neutron scattering technique was used to study the dynamics of monolayer protected metal cluster superlattice and isolated cluster systems, and it was found that the chains participating in the inter-cluster interaction were dynamically different from those without.

Abstract: Alkyl chain dynamics in monolayer protected metal cluster systems has been studied by the quasielastic neutron scattering technique, using two different instruments having very different energy windows. Long chain thiolate protected clusters such as Au–ODT (Au–SC18H37) are rotationally frozen at room temperature (RT) in a wide time scale of 10−9 to 10−12 s. The rotator phase is absent at RT even in much smaller chain length systems, Au–OT (Au–SC8H17) and Au–HT (Au–SC6H13). Dynamics was found to evolve upon increase in temperature. Alkyl chains in a metal cluster superlattice such as Ag–ODT (Ag–SC18H37) are also dynamically frozen at RT in the whole time scale range. Evolution of dynamics with temperature is found to be different in the superlattice and isolated cluster systems. In the former, the chains participating in the inter-cluster interaction were found to be dynamically different from those without. On heating just above the chain melting temperature (Tcm), chains not involved in the inter-cluster...