Casting method was employed to prepare films of poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) (PVVH) copolymer doped with different concentrations of tetrabutylammonium tetrafluoroborate ([TBA][BF4]) electrolyte. The interaction between copolymer and electrolyte was clearly evident in the reduction of FTIR peaks intensity at 1666 and 1729 cm-1 with increasing electrolyte concentration. This reduction was related to the deacetylation of PVVH by the electrolyte. Effect of deacetylation was also visible in the reduction of DTG/DTA peak temperature (Tp) of the second stage of the composites. The reduction of DSC glass transition temperature (Tg) from 344 K to 310 with increasing electrolyte content was another evidence of the deacetylation effect that reduces the inter- and intramolecular interaction maintaining flexibility of PVVH copolymer backbone to bend and slide more readily. Based on the aforementioned results, one can assume that [TBA][BF4] electrolyte acts as an external plasticizer for PVVH that is internally plasticized by random copolymerization of vinyl chloride (VC) with vinyl acetate (VAc) and 2-hydroxypropyl acrylate (2HPA) to reduce the Tg of VC from 355 to 344 K. Another reduction was observed in the optical energy gap (Eg) with increasing the electrolyte content. Linear and nonlinear optical parameters were estimated and discussed in terms of the single oscillator model. Besides, the optical conductivity (σop) and dielectric constant of all samples were investigated.