Nanophase separation and exotic dynamic behavior in comb-like polymers

We show the potential of neutron scattering combined with isotopic labeling to unravel structural and dynamical properties of “comb-like” polymers. Results on homopolymers with alkyl side groups of varying length, namely on the families of poly(n-alkyl methacrylates) (PnMAs) and poly(alkylene oxides) (PAOs) are summarized. Diffraction experiments and fully atomistic molecular dynamics simulations evidence the formation of self-assembled nanodomains of the side groups surrounded by the main chains, independently of the nature of the latter. Neutron spin echo, time of flight and backscattering techniques were employed to investigate the collective dynamics relating inter- and intra-nanodomain correlations as well as the incoherent scattering function of hydrogens. The results are combined with other experimental techniques-dielectric spectroscopy and differential scanning calorimetry- to put into a context the dynamical processes identified. Plasticization and confinement effects arise in PnMAs, but not in the PAOs counterparts. The results point to the dynamic asymmetry developed in systems with intrinsic dynamic heterogeneities between the constituent parts as the key ingredient leading to the main features observed in PnMAs. This scenario is supported by coarse-grained simulations on generic comb-like polymers.Financial support from the projects MAT2012-31088 and IT-654-13 (GV) is acknowledged.Peer reviewe