*Article* **The Effect of PVP on Thermal, Mechanical, and Dielectric Properties in PVDF-HFP/PVP Thin Film**

**Urška Gradišar Centa 1,\*, Mohor Mihelˇciˇc 1, Vid Bobnar 2, Maja Remškar <sup>2</sup> and Lidija Slemenik Perše <sup>1</sup>**

<sup>1</sup> Faculty of Mechanical Engineering, University of Ljubljana, Aškerˇceva 6, 1000 Ljubljana, Slovenia

<sup>2</sup> Institut Jozef Stefan, Jamova 39, 1000 Ljubljana, Slovenia

**\*** Correspondence: urska.gradisarcenta@fs.uni-lj.si

**Abstract:** In this research, the influences of the addition of PVP to PVDF-HFP polymers and the preparation of thin films using a solvent casting method were studied. The PVDF-HFP and polymer blend PVDF-HFP/PVP thin films with a nanostructured surface were investigated using scanning electron microscopy, differential scanning calorimetry, nanoindentation, and dielectric spectroscopy. The results showed that the PVP formed a dispersed phase (the poorer conductive islands) in the PVDF-HFP polymer matrix, which reduced its mechanical properties. The crystallinity of PVDF-HFP polymer decreased with the addition of PVP by 7.4%, but the PVP induced the formation of the polar β-phase of PVDF-HFP. Therefore, an improved dielectric response is expected, but it was not significantly improved even though the polar β-phase was detected. The contrasting effect was attributed to less conductive PVP islands on the surface of the PVDF-HFP/PVP polymer blend, which decreased its conductivity.

**Keywords:** polymer blend; PVDF-HFP; PVP; mechanical properties; crystallization
