Among the five distinct polymorphs of polyvinylidene fluoride (PVDF), β-PVDF is of the highest technological importance due to its exceptional electro-active properties. But β-PVDF polymorph is difficult to synthesize due to its structural instability. Addition of ionic liquids in PVDF blend is found to enhance β phase crystallization. Here dispersion corrected density functional theory (DFT-D) study is carried out to demonstrate the effect of adding 1-n-alkyl-3-methylimidazolium-tetrafluoroborate ([CnMIM][BF4][n=2,4,6,8,10]) ionic liquids on the structure and properties of β-PVDF. Calculated IR and Raman spectra for all the systems show excellent match with experimental results. Calculation of interaction energies, dipole moment and polarizability, population analyses (Mulliken and Hirshfeld), molecular electrostatic potential and natural bond orbital analyses are performed to characterize the interaction, charge transfer and piezoelectric properties of the systems. Frontier orbitals (HOMO-LUMO) composition and energies are obtained to demonstrate the variation in chemical hardness, softness, potential, electronegativity and electron affinity of the systems.