Investigation of structural relaxation and surface modification of ultrathin films of poly(ethylene terephthalate)

We studied dynamic properties of ultrathin films of poly(ethylene terephthalate) spincoated on different substrates, by means of dielectric spectroscopy and surface patterning experiments. We did not observe any variations of structural dielectric relaxation dynamics for films spincoated on aluminium substrate having thicknesses down to 40 nm. On the same substrate, 13nm thick films are instead characterized by a reduction of the chains mobility. Surprisingly the chains dynamics as probed by a surface nanopatterning experiment evidenced a strong dependence on the substrate interaction even for 50 nm thick films, where dielectric relaxation dynamics is unaffected. It can be deduced that different length scales characterise dielectric relaxation dynamics and the processes related to the surface patterning, even if both are related to the chain mobility. Further experiments are wished to better understand this intriguing scenario.