Cooperative rearranging region and dynamical heterogeneity of nanocomposites in poly(l-lactide) and functionalized carbon nanotubes systems

The study of the cooperative rearranging region and the rheological behavior was undertaken to evaluate the dynamics of nanocomposites constituted by chain extended poly(L-lactide) (PLLA) and multiwalled carbon nanotubes (MWCNTs). Temperature modulated differential scanning calorimetry (TMDSC) and melt rheology were specifically employed to study the dynamics of polymer chains in amorphous solid state and liquid state, respectively. Results indicated that addition of functionalized MWCNTs increased chain rigidity leading to an increase of the size of cooperativity, although glass transition temperature could remain constant. Rheological measurements demonstrate significant variation of the modulus and viscosity of nanocomposites. Similar to Cole-Cole plot and semi-circle equation in dielectric measurements, an equation is presented to recognize the amount of heterogeneity in nanocomposite systems according to rheological data. Overall results indicate that the dynamical heterogeneity of PLLA was clearly changed by both factors: polymer chain extension and MWCNT functionalization.