Nanoparticle Effects on Polymer Crystallization and Dynamics.

摘要

Polymer mixtures, copolymers, and structurally designed polymers have been joined by the incorporation of nanoparticles as a method of tuning material properties. The research presented here examines the properties of polymer nanocomposites in terms of nanoparticle effects on polymer crystallization and dynamics. The objective of this work is to further the understanding of the ways in which nanoparticles affect polymer properties in order to enhance development of polymer nanocomposites with desired properties through the controlled addition of appropriate nanoparticles.;In examining the effect of single-walled carbon nanotubes (SWNTs) and organically-modified layered silicates (OMLS) on the crystallization process and final morphology of the semi-crystalline polymer poly(vinylidene fluoride), a synergistic result is observed wherein the piezoelectrically active beta-phase is promoted while the native alpha-phase is hindered. Furthermore, the resultant electrical properties indicate further benefit from optimized in and out of plane dielectric vs. conductive behavior.;The second part of the work attempts to distinguish between nano-confinement and interfacial interactions as the dominating factor in the observed phenomenon wherein polymer glass transition temperatures (Tg) are shifted up or down in glass-forming amorphous liquid and polymer systems. A new approach is used involving different nanoparticle geometries to represent different modes of interaction with the polymer. Behavior is distinguished between what occurs at different length scales and temperatures. Near and above Tg, neutron scattering experiments reveal that the dynamics are dominated by the confinement of the polymer chains rather than by their interactions with nearby interfaces.