Preparation of vertically oriented aromatic polyester thin films by thermal chemical vapor deposition

Aromatic polyesters exhibit high thermal conductivity and large nonlinear optical effects by controlling the orientation of their main chains. Especially in recent years, with the development of flexible optical and electronic devices utilizing polymer thin films, out-of-plane orientation control in thin films on the order of several hundred nm is required. However, due to the rigidity of aromatic polyesters, it is difficult to control vertical orientation in thin film growth from melt or solution. In this study, we attempted to control the vertical orientation of aromatic polyester thin films from the vapor phase using a thermal chemical vapor deposition. From a single head-to-tail type monomer, aromatic polyester thin films with the most primitive structure, whose melting point exceeds 500°C, were successfully grown. Furthermore, it was found that the vertical orientation of the main chains was enhanced by substrate surface treatment.