Topic:  Microstructural Design in Polymer Nanocomposites:  Effects of Matrix Crystallinity and Interfacial Chemistry

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.

 Speaker:  Dr. Meisha L. Shofner is an Assistant Professor in the School of Materials Science and Engineering at Georgia Institute of Technology, joining the faculty following post-doctoral training at Rensselaer Polytechnic Institute.  She received her B.S. in Mechanical Engineering from The University of Texas at Austin and her Ph.D. in Materials Science from Rice University.  Prior to beginning graduate school, she was employed as a design engineer at FMC in the Subsea Engineering Division, working at two plant locations (Houston, Texas and the Republic of Singapore), and she is a registered Professional Engineer in Georgia.  Dr. Shofner currently serves as the secretary of the TMS Composite Materials Committee and as a member of ASME’s Nanoengineering for Energy and Sustainability Steering Committee.  At Georgia Tech, Dr. Shofner’s research group is concerned with structure-property relationships in polymer nanocomposite materials and with producing structural hierarchy in these materials for structural and functional applications.  This research has been recognized by the Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associate Universities and the Solvay Advanced Polymers Young Faculty Award.