Hi all, It is well known that poly(3-hexyl thiophene) and other conductive polymers with alkyl substituents align when deposited on a surface (e.g. by spin coating or drop casting). The common orientations for P3HT on silicon/silicon dioxide are "edge-on" in which the alkyl side-chains point normal to the surface, and "face-on" in which the thiophene rings lie parallel to the surface. I have read quite a few papers that discuss this observation, for example these two highly cited Nature articles:  http://www.nature.com/nature/journal/v401/n6754/full/401685a0.html  http://www.nature.com/nmat/journal/v5/n3/full/nmat1590.html My question is: what is the exact energetic reason for this alignment. The "edge-on" alignment is most common and my rationale for this is that the SiO2 surface is quite polar. The aromatic thiophene rings are more hydrophobic than the alkyl tails, thus it is favourable for the polymers to stand up such that the thiophene rings do not interact with the substrate. The second article I posted does discuss the mechanism a little but I am looking for a good reference that explains this phenomenon. Many thanks.