Nanophase separation and anomalous dynamic behavior in comb-like polymers

Resumen del trabajo presentado al 7th International Discussion Meeting on Relaxations in Complex Systems: "New results, Directions and Opportunities", celebrado en Barcelona (España) del 21 al 26 de julio de 2013.We present a comparative study of the structure and dynamics of two series of 'comb-like' polymers: poly(alkylene oxides) (PAOs) and poly(n-alkyl methacrylates) (PnMAs). In both cases, polymers with increasing length of the side groups are investigated, being the difference between the two families the rigidity of the main chain. Different experimental techniques are employed, including a variety of neutron scattering methods. These, together with isotopic labelling, have allowed the selective study of main-chain and side-group properties. Self and collective motions are probed. Complementary fully atomistic and coarse-grained molecular dynamics simulations have also been carried out. The structural features developed in both series are identical, characterized by nanosegregation of alkyl side groups and main chains. Contrarily, the dynamic properties of side groups within the nanodomains are strikingly different depending on the main-chain nature. They show typical confinement effects in PnMAs, which are attributed to the development of a strong dynamic heterogeneity. The purely entropic origin of the self-assembled nanostructures and the decisive influence of the dynamic asymmetry are confirmed by the coarse-grained model.Peer Reviewe