Factors influencing the growth and topography of nanoscale films fabricated by ROMP-mediated continuous assembly of polymers

Abstract

The continuous assembly of polymers (CAP) mediated via ring-opening metathesis polymerization (ROMP) is demonstrated as a simple and versatile method to fabricate tailored nanostructured thin films. The film thickness and topography were highly dependent upon the variation of different factors that influence the ROMP reaction and mechanism of the assembly process. Herein, we present a detailed investigation of the influence of various parameters on the rate of film formation, the film thickness and the film topography. Whereas the macrocross-linker concentration and molecular weight determined the final film thickness and surface coverage, the initiator concentration and ROMP catalyst activity were found to have a negligible effect on the film properties. Importantly, the minimum amount of polymerizable moieties required in the macrocross-linker to obtain fine control over film thickness and high surface coverage was found to be 7 mol%. The addition of excess ligand (≤100 mM) for the catalyst increased the catalyst lifetime leading to thicker films, although further increases (>100 mM) were found to retard the metathesis reaction. These findings provide valuable insights into the CAPROMP process and will contribute toward developing the next generation of CAP ultrathin films for advanced applications.