Title

The Effect and Role of Functional Groups in the Compatibilization of Immiscible Polymer Blends: Investigation of Blend Morphology, Properties and Thermodynamics

Date of Award

2005

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Robert B. Moore

Advisor Department

Polymers and High Performance Materials

Abstract

The underlying theme through all of the facets of this project is the effect of functional groups on the morphology and properties of polymer systems, specifically when applied to the compatibilization of immiscible polymer blends. The functional groups range from grafted acid and maleic anhydride units to sulfo-isophthalate groups polymerized into the polymer backbone. In order to capitalize on the possibility for specific intermolecular interactions between blend components, compatibilization of blends of polar polymers, such as polyester and polyamide, was investigated. Initially, the project focused on improving the thermal and mechanical properties of poly(L-lactide) (PLLA) with the goal of extending the temperature range of use for the polymer while maintaining its degradability. The research employed reactive extrusion techniques to graft functional groups, either maleic anhydride or acid-functional peroxides, onto the backbone of PLLA in order to use the functionalized polymers as compatibilizers in degradable blends of PLLA with cellulose acetate or polyamide 6 as well as degradable clay nanocomposites. The course of the project then shifted to an investigation into the use of polyester ionomers as compatibilizers in amorphous polyester/polyamide blends. The research built upon the results of previous polyester/polyamide compatibilization studies, but was carried out using amorphous blend components in order to more clearly elucidate the morphology of the blends along with the interactions and thermodynamics that govern it. In investigating the morphology of the ionomer-compatibilized blends, not only was a reduction in domain sizes observed but also a shift in the morphology from a droplet/matrix to co-continuous structure occurred at higher loadings of the ionomer. From literature research, this was presumed to be caused by a reduction in the interfacial tension between the blend components with the incorporation of the ionomer compatibilizer, though such a trend with ionomers had never been reported. Thus, direct determination of the interfacial tension in both the presence and absence of ionic functional groups was carried out using imbedded fiber retraction experiments. Further investigation of the polyester/polyamide blend system involved extending the use of synchrotron small angle x-ray scattering into the characterization of the morphology and domain sizes as a function of the incorporation of ionic functionality. The research was based on literature reports discussing the use of synchrotron SAXS and SANS to investigate the morphology of heterogeneous polymer systems, in particular block copolymers and IPN's. In this investigation, synchrotron SAXS was found to be useful in the investigation of blend morphology with results showing trends similar to those observed in previous experiments. (Abstract shortened by UMI.)