Unraveling the Effects of Molecular Confinement on the Dynamics of Polymeric Systems: I. Block Copolymer Architecture II. Silica Nanopores

In this dissertation, broadband dielectric spectroscopy (BDS) is employed as an experimental tool to probe dipolar relaxations in polymeric systems under two types of molecular confinement. First a series of miktoarm star copolymers are used to explore how branching block copolymer architectures constrain polymer relaxations within self-assembled domains in relation to linear systems. Secondly, the effects of hard spatial confinement on the dynamics of polymer chains and of ions in polymerized ionic liquids (PILs) are studied after infiltration into silica nanochannels. Complementary techniques such as transmission electron microscopy, small angle x-ray scattering, and Raman spectroscopy are used to determine various structural length-scales and molecular conformations of the molecules in these systems. The model system of poly(cis-1,4-isoprene) (PI) is employed to probe polymer chain dynamics by BDS. The local and cooperative dynamics of the PI homopolymer are used to compare and identify dynamical changes under confinement. Additionally, surface chemistry modifications are used to study electrostatic interactions between ions and the substrate in hard spatial confinement studies. It is determined that an asymmetrical molecular architecture of the miktoarm star copolymer is more influential on the PI chain dynamics and reduces thermodynamic constraints on individual blocks compared to symmetric architectures. These decreased confinements are correlated to alterations in chain density allowing PI chain stretching energies to decrease as described by the Gaussian chain model of block copolymers. Similar changes in density are also revealed within the nanopores for PI and PILs corresponding to slower chain relaxations and enhanced ionic conductivity, respectively, compared to the bulk homopolymers. These dynamical changes for confined polymeric systems are discussed in correlation to macroscopic properties that are important for materials science applications.