(621c) Thin Film Crystallization of Cyclic Polymers and Their Linear Analogues 

While the crystallization of linear and branched polymers has received much attention in the literature due to the importance of polymers like linear poly(ethylene glycol) to the biological sciences and branched polyethylenes to the commodity polymers market, the effect of ring architecture on polymer crystallization is less well understood, in part due to the challenges associated with synthesizing well-defined cyclic polymers. However, recent advances have enabled the synthesis of cyclic polymers with exact linear analogues using an azide-alkyne “click” reaction for ring closure and prompted additional research into the properties of cyclic polymers. With respect to semi-crystalline polymers, literature on bulk materials indicates that cyclic polymers have faster crystallization kinetics and greater thermal stability than linear polymers. In this work, we focus on the differences between linear and cyclic polymers under thin film confinement, which leads to deviations from bulk behavior. Specifically, we compare the thin film stability, thermal transitions (melting temperature and equilibrium crystallization temperature), crystallization kinetics, and morphologies of cyclic and linear thin films. As a model system, we have chosen poly(ε-caprolactone) (PCL), a semi-crystalline, aliphatic polyester that has applications in biomedical engineering including anti-adhesion biomaterial films, drug delivery media, and others.