(Georgia Institute of Technology, 2012-09-25)
Shofner, Meisha L.
Structure-property research in polymer nanocomposites has often focused on producing systems that are
homogeneously dispersed in order to capitalize on the large amount of specific surface area available from
nanoparticles. However, inhomogeneous dispersion is often obtained and in some cases has been deliberately
sought to enhance functional properties through the formation of particle networks. In this research, we are
exploring matrix-mediated methods for directing nanoparticle dispersion. Specifically, we are examining
dispersion behavior of calcium phosphate nanoparticles of different shapes in semi-crystalline polymer
matrices. Our results have shown that nanoparticle arrangement is influenced significantly by the matrix
morphology. In matrices with moderate levels of crystallinity, high levels of nanoparticle dispersion are
attainable and reinforcement behavior is temperature dependent, similar to amorphous matrices. However at
higher crystallinity levels, nanoparticles have a strong tendency to aggregate into larger structures whose
shape is related to the native nanoparticle shape. This tendency can be mitigated by changing the surface
chemistry through copolymer compatibilization. Experimental results concerning the effect of particle
aggregation and shape on polymer crystalline structure, thermal transitions and mechanical properties are
presented to more fully understand nanocomposite structure-property relationships from the perspective of
the polymer matrix.