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

Abstract

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 (similar to 94%, only 20% lower than pure PVA) up to PEDOT:PSS fractions of similar to 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.