Thin Film Melt Stability of Cyclic Poly(ε-caprolactone)

Until recently, studies on semi-crystalline polymers focused on the physical characterization and applications of purely linear or branched polymers. However, synthetic advances have now enabled the production of high purity cyclic polymers using copper catalyzed alkyne-azide click (CuAAC) coupling, thus enabling phenomenological study. In this work, we describe the finding that cyclic poly(caprolactone) resists thin film dewetting better than its linear analogue. A systematic study was conducted to understand this phenomenon on the basis of linear end group chemistry via synthesis of linear PCLs containing triazole groups and terminated with hydroxy, propargyl, azide, and acetyl groups. However, only the cyclic PCL film retained stability in the melt. Ongoing work is focused on further describing the fundamental origin of this stability. GIWAXS and GISAXS experiments will allow us to quantify subtle differences in the crystal lattice as well as the lamellar spacing and orientation relative to the substrate, which may play a role in stability. Developing a better understanding of how chain topology affects thin film stability and using what we learn to enhance the stability of polymers in thin films has the potential for enormous impact on the future of thin film applications.