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Structure-Electrical Transport Property Relationship of Anisotropic iPP/CNT Films Parvathalu Kalakonda1, Michael Daly2, Kaikai Xu2, Yaniel Cabrera3, Robert Judith3, Germano *

S. Iannacchione1, Georgi Y. Georgiev1,2 and Peggy Cebe3 1

Department of Physics, Worcester Polytechnic Institute, Worcester, MA 01609, USA Department of Natural Sciences - Physics, Assumption College, Worcester, MA 01609, USA 3 Department of Physics, Tufts University, Medford, MA 02155, USA *corresponding author: [email protected]; [email protected] 2

ABSTRACT The internal micro/nano-structure of anisotropically oriented polymer/CNTs composites determines their macroscopic properties. However, the connections between the two are not fully understood. The varying of CNT concentration, preparation method, and a thermodynamic parameter (e.g. temperature) can all play interconnected role. In this work, the macroscopic electrical conductivity was measured perpendicular to the film thickness of an insulating polymer (isotactic PolyPropylene, iPP) and a nano-composite of iPP with 5 weight percent of CNT. The thin films studied were sheared (anisotropically nano-structured) and non-sheared (with random internal structure). In general the effect of melt shearing induces anisotropy on the electrical transport properties of the iPP/CNT films in directions parallel and perpendicular to the direction of orientation. Our results show that for the pure iPP, resistivity slightly increases with shear at higher temperatures. When CNTs are introduced, there is a large difference between the resistivity of the sheared and non-sheared nanocomposite. The sheared PNCs when the CNTs are aligned parallel to each other, have higher resistivity, which is possibly due to the higher concentration at which the percolation threshold occurs in this arrangement. The resistivity decreases overall, as the temperature increases from 0 to 50 oC. These results show that CNTs can be used to control and fine tune the desired macroscopic physical properties of nanocomposites, by concentration and orientation, such as electrical conductivity, for applications where such properties are necessary. INTRODUCTION The questions explored in this study are aimed at the interplay between nanoscale and macroscale phenomena in thin polymer/MWCNTs nano-composite (PNC) films. Macroscale manipulation, like melt-shearing of PNCs, can induce nanoscopic order of the MWCNTs and polymer chains [1]. Here, it is investigated how the induced nanoscopic orientational order of MWCNTs and polymer chains affects one macroscopic property, namely the electrical conductivity of the films and its anisotropy [2, 3]. There are many factors that can affect the percolation of MWCNTs, like concentration, dispersion and size. The orientational order of MWCNTs is another factor which can influence the critical concentration when MWCNTs start forming networks. The concentration is varied and the induced electrical anisotropy in oriented nano-composite films under identical melt-shearing conditions is measure