http://www.sciencedirect.com/science/article/pii/S0144861714011163

i hope this paper help u.

Do you mean together in the same solution or separately?

what's  the solvent system ? You know the solvent plays an important role in electrospinning.

the solvents are acetic acid and formic acid and they are both dissolved together but chitosan is just 0.5% of this solution. 

I would guess that your voltage could be too low.  Can you adjust the tip-to-collector distance to increase the effective field strength?

if content of chitosan is high, it would be better to increase voltage up to 20kv. if pcl is high keep voltage around 12-15 kv. but i think it easily works as u have chosen good solvents. try to adjust electrospinning parameters. 

good luck

May be U can try to use the  Hexafluoroisopropanol(HFIP) and  acetic acid as your solvent system.