{HEAD ~ a polymer outer layer} coupled to {TAIL ~ the first metallic material} opposite the substrate, and 
coupled to
{ HEAD ~ a polymer outer layer } coupled to { TAIL ~ the first metallic material } opposite the substrate , and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH