Mechanical characterizations of cast Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)/Polyvinyl Alcohol thin films

The polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate), hereafter referred to as PEDOT:PSS, has electrical properties superior to those of most conducting polymers, but it is too brittle to be employed in many applications. Blending PEDOT:PSS with other polymers is a promising route to reach a good trade-off between electrical and mechanical properties. This paper describes the mechanical characterization of PEDOT:PSS/PVA (Polyvinyl Alcohol) blends. The PEDOT:PSS/PVA films used in this study are produced by casting, and uniaxial tensile tests are performed to characterize the Young`s modulus, fracture strain, tensile strength, and plastic deformation behavior of the blends as a function of the weight fraction of the components. For pure PVA, the Young`s modulus, fracture strain and tensile strength are found to be, respectively, 41.3 MPa, 111% and 41.3 MPa. The strength exhibits a nearly perfect bimodal behavior, suddenly increasing by a factor 2 at a PEDOT:PSS content of 30%. Importantly, the ductility remains extremely high (∼94%, only 20% lower than pure PVA) up to PEDOT:PSS fractions of ∼50%. The Young`s modulus monotonically increases with PEDOT:PSS content, reaching 1.63 GPa at 50%. SEM imaging and XRD analysis allows correlation of these evolutions to substantial morphological changes in the PEDOT:PSS/PVA microstructure. When combined with a previously published electrical characterization study, the current work suggests that a PEDOT:PSS/PVA polymer blend with 30–40 wt% of PEDOT:PSS provides the best trade-off of conductivity and ductility. For non free-standing films, higher PEDOT:PSS fractions (70%) might be preferable.