Nanomechanical properties of poly(para-phenylene vinylene) determined using quasi-static and dynamic nanoindentation

Mechanical properties of poly(p-phenylene vinylene) (PPV) were determined by quasi-static and dynamic nanoindentation. PPV films were prepared by thermolytic conversion of poly[p-phenylene (tetrahydrothiophenium)ethylene chloride] precursor films, at different temperatures. The mechanical properties of the films showed a dependence on the extent of conversion and chemical composition of the films. The storage modulus, E-r', and plasticity decreased with an increase in conversion, whereas the loss modulus, E-r '', showed the opposite trend. Both the precursor and the fully-converted PPV films were found to have significantly lower E-r '' than E-r', consistent with the glassy nature of the polymers at room temperature. The fully-converted PPV polymer was found to have room-temperature storage and loss moduli of 4.4 and 0.2 GPa, respectively. A comparison of the contact mechanical properties of the isotropic PPV films synthesized in this work with previously reported values for stretch-oriented anisotropic films determined by conventional tensile testing methods is also discussed. (C) 2014 Elsevier Ltd. All rights reserved.