Dear Ümran Aşçı, many possible reasons:

- poor evaporation of the solvent

- low viscosity due to: low MW, low concentration

- inadequate applied voltage

And many other process parameters. My Regards

Dear Abdelkader BOUAZIZ, thank you for your answer.

Dear Ümran Aşçı, no thanks, if you give more details may be I Can help you more. My Regards

Hi;

The formation of electrospun fibers is mainly determined by the processing parameters, including the applied voltage, the flow rate of the liquid, solution viscosity and the distance between the tip of the spinneret and the collector. It is then important to optimize all the processing parameters in order to control an electro-spinning process. For more information, please see the link below:

doi: 10.1021/acs.chemrev.8b00593

With my best regards

Doufnoune RACHIDA Rachida Thank you very much.

Maybe the solvent still not evaporating due to the small Tip-collector distance this will make the fibers stick together like film

Ahmed Amer Flayeh I've tried different distance values actually (including greater distance values) and all of them resulted in film.

What is your solvent?

Timucin Balkan I've been using 1,4 Dioxane/DMF solvent system. I know both of the solvents have high boiling points and low evaporation rate. I tried to dry my samples after the electrospinning process but got the same SEM results.

Dear Ümran Aşçı, the following RG thread may bring additional information. What is the polymer you are dealing with ? Each polymer has specific conditions whether a fibers or film is to be produced. My Regards

https://www.researchgate.net/post/Why_do_I_get_formation_of_films_in_electrospin

Abdelkader BOUAZIZ I am currently working on electrospinning of PLA with 5 % D-lactide stereoisomer content, weight average molecular weight (Mw) of 278000 and polydispersity (Mw/Mn) of 1.78 . Regards.

Please check attentively the following documents. It is advisable to understand under which conditions films are produced via electrospinning, this way one get an idea about the permissible window to produced either fibers or films. Again what is the order of MW. My Regards

https://doi.org/10.1016/j.fpsl.2019.100357

https://doi.org/10.1155/2013/409572

https://www.researchgate.net/publication/341088526_Electrospinning_of_PLA_with_DMF_Effect_of_polymer_concentration_on_the_bead_diameter_of_the_electrospun_fibre

https://www.researchgate.net/publication/332309628_I_Film_Using_Electrospinning_to_Create_Bioactive_Films

Ümran Aşçı, why did you prefer to use this solvent mixture? as you mentioned both have high boiling points. In my opinion, you can work with a MeOH/DMF (ratio will be important because I am not sure about the solubility of PLA in MeOH) mixture which helps to decrease the surface tension of your solution and hence enhances the formation of nanofibers. In our previous study, we worked on PLA/PCL nanofibers and CHCL3/MeOH solvent system was used. Article Incorporation of growth factor loaded microspheres into poly...

Timucin Balkan I've used CHL/DMF solvent system for my previous studies, however i've faced with drying jet problems due to the low boiling point and rapid evaporation of chloroform even in low polymer concentations like 5wt%. Therefore, i needed to change the solvent system.