PBC would be a great post for the near future! Thanks for the idea 🙂
Now, to answer your question. PBC generates a periodic model from a small set of atomic coordinates based on symmetry considerations you impose. Therefore you can run calculations on a polymer based on the calculations of the corresponding monomer (1D replication). The same holds true for a surface (2D replication) or a crystalline solid (3D). The problem is getting the band structure of the solid which could be obtained as a result of a (very demanding) DFT calculation in which the MOs would get so packed they would constitute a band.
I would suggest to get another software such as CRYSTAL but PBC in G09 could be a great first step in calculating the electronic structure of a solid.