In the following links you can find lipid coordinate and topology files for lipids:  http://wcm.ucalgary.ca/tieleman/downloads 

http://mmkluster.fos.su.se/slipids/Downloads.html

https://sites.google.com/site/anirbanzz/gpcr-gromacs-tutorial

Using pdb2gmx command can be created mostly protein topology. Lipid (not all of them) and polymers topology is not included in the gromacs database. For your polymer case, just use one of the online automatic topology builders such as https://atb.uq.edu.au/index.py 

If you have further questions just let me know. 

Thanks Jamoliddin Razzokov, for providing valuable information.