Hi Zheng,

Check the following link. You can download it as PDB file format.

http://www.chemtube3d.com/polymer/_KaptonF.html

hi check the link below:

http://www.ebi.ac.uk/chebi/advancedSearchFT.do

https://ncit.nci.nih.gov/ncitbrowser

You first do geomtry optmization in gas phase. You can use Gaussian/Games

for this. 

Thank you guys for reply. I appreciate it a lot.

Yoshinobu, I have downloaded the pdb file, which is the polymer file. Do you know how to download just monomer file? There is option for "Show single repeating unit ". But when I try to download, it is still the whole polymer.

Thanks!

Soroush, the first link you provide has polyimide but only general information is provided. Did I miss anything? How to obtain atomic coordinates there?

Could you please clarify on this with more details?

Thank you very much.

Hi Zheng,

To get a monomer file, you should delete unnecessary atoms in its PDB file by a text editor.

To know atom numbers, try Jmol:

http://jmol.sourceforge.net/

if there is a pdb file you can use this:

https://www.rcsb.org/pdb/search/refine.do?qrid=A0A48884

Soroush, thank you very much for help. But I am not so lucky. Kapton polyimide is not in that database.

Yoshinobu, 

Thanks, I'll try it.

Best, 

Zheng