you can try dopamine as well

I assume by PAN you mean polyacrylonitrile. APTES is not a great choice, it will be a crosslinked network, but it won't be covalently attached to the surface. Perhaps you could use a plasma source to activate it, then use a silane. The dopamine route is the same idea, it wont be a covalent interaction unless you activate it. Both of these are alkyl amines too.

For getting to your aniline derivative:

Amino benzophenone plus UV light would be an excellent choice, though it would only functionalize where the UV light penetrates.

For some fancier, but very robust and complete functionalization of your substrate sulfonyl azides plus thermal curing above 120C can functionalize anything with a C-H bond. For easy access to an aniline sulfonyl azide, you could deacetylate this: http://www.sigmaaldrich.com/catalog/product/aldrich/404764

dear Jeremy Yatvin and Ali Pournaghshband , thanks for your answers. Actually I will grow a membrane on this support so perhaps functionalization of the whole surface will be important in order to grow a continuous membrane. Can you please provide a reference to the functionalization route through aniline sulfonyl azide. Thanks

If you look at my profile you can see polymer work I've done with sulfonyl azides.  My work was based off this polymer paper by ruhe http://pubs.acs.org/doi/abs/10.1021/ma801387e

This could also be a helpful for you. It's using heat and azides to functionalize a membrane http://onlinelibrary.wiley.com/doi/10.1002/marc.201400226/abstract

The patent literature has older examples of using small disulfonyl azides as cross links as well. 

I spoke with Oswald prucker and he said that it only takes a few minutes at 180C to do functionalization. 

thank you very much dear Jeremy Yatvin