A Study on the Chain-Particle Interaction and Aspect Ratio of Nanoparticles on Structure Development of a Linear Polymer

The stability of metastable flow-induced precursor (FIPs) in the polymer melts in presence ofnanoparticles, viz. single-walled carbon nanotube (SWCNT) and zirconia nanoparticles, is studied at, 142 _C,close to the equilibrium melting point of unconstrained extended chain crystals of linear polyethylene (PE).The results conclusively demonstrate the influence of chain-particle interactions, between PE and thenanoparticles, on the stretch of the long chains. With the applied flow, SWCNTs together with PE chains areobserved to align along the flow direction, giving rise a strong streak like pattern along the equator. At theinitial stages, intensity of the observed streak in the presence of SWCNTs is stronger than that for the neatpolyethylene. The streak intensity stabilizes with time, where the time required for the stabilization dependson the amount of the dispersed nanotubes in the polymer matrix. On the contrary, in the presence of zirconiananoparticles, where the chain-particle interactions between PE and the nanoparticles are weak the initiallyobserved streak tends to disappear with time, where the time required is strongly dependent on theconcentration of the nanoparticles in the polymer matrix. Thus, compared to the neat polymer, the presenceof zirconia nanoparticles destabilizes the shish formation. The chain orientation along the flow direction isdetermined using Herman’s orientation function and the length of the oriented chains (shish) by Ruland’sstreak analysis. On cooling, with the crystallization of the polymer, scattering develops along the meridian,indicating the development of folded chain crystals, where the oriented chains present along the flow directionprovide the epitaxy matching thus suppressing the nucleation barrier. The meridional intensity (arising withthe formation of crystals, called kebabs) at room temperature, shows strong dependence on the stable streakintensity (chain orientation along the flow direction, called shish) along the equator prior to cooling.