In this work, electrospinning technique has been used to produce a new ultra-fine hybrid fiber from a solution consists of polystyrene (PS) and epoxy polymers in dimethylformamide (DMF) solvent. Five ratios of different weight percentages of epoxy in PS/DMF solutions of 4 different concentrations; 15, 20, 25 and 30wt.% were made to obtain the minimum diameter of the produced hybrid fiber. The minimum obtained hybrid fiber diameter was found to be 897 +/- 239nm at a PS/epoxy ratio of 5:1 and 13.33 Berry's number. Adding epoxy to PS has reduced the electrospun fiber diameter from 2.64 +/- 0.49m for PS only to 1.52 +/- 0.72m for PS/epoxy hybrid ultra-fine fibers because of the reduction in Berry's number from 12.4 to 11.53, which gives an indication for the effect of adding epoxy on the PS molecular chain entanglement in DMF. Nuclear magnetic resonance spectroscopy results unambiguously reveal the coexistence of both epoxy and PS polymers in the hybrid fiber. We hypothesize that a hydrophopic (-) interaction between the benzene rings of PS and epoxy polymers could contribute to the stability of the resulting hybrid fiber under electrospinning conditions. The fact that the lack of functional groups on both of PS and epoxy polymers that can results in covalent bonding or crosslinking between the 2 polymers supports the hypothesis of hydrophopic (-) interaction in the stability of the hybrid fiber. Such (-) interaction is well known to contribute to DNA single strand helical structure via intrastrand staking of the consecutive purine and pyrimidine nucleobases.