Quantitative Viscoelastic Mapping of Polyolefin Blends with Contact Resonance Atomic Force Microscopy

The storage modulus (E') and loss modulus (E '') of polyolefin blends have been mapped on the nanoscale with contact resonance atomic force microscopy (CR-FM), a dynamic contact mode of atomic force microscopy (AFM). Modulus values measured on various components within a blend of polyethylene, polypropylene, and polystyrene compared favorably with expected moduli of individual pure components at the contact resonance frequency that were calculated from bulk dynamic,mechanical analysis (DMA) measurement results. Absolute storage modulus values were in good agreement with DMA results, while the loss modulus values obtained from CR-FM were consistently lower than those acquired from DMA Application of CR-FM to an elastomer-containing blend resulted in moduli map artifacts due to the elastomer's high adhesion and low storage modulus, illustrating its limitation in quantifying viscoelastic properties of soft elastomers. In spite of this current limitation, the results presented in this paper demonstrate the potential of contact resonance methods for quantifying nanoscale viscoelastic properties of certain thermoplastic polymers.