Temperature-Responsive Thin Films from Cellulose Stearoyl Triester

In comparison to synthetic thermoresponsive polymers, thermoresponsive materials based on naturally occurring polysaccharides and in particular cellulose are scarce. In this study, thermoresponsive hairy-rod polymer, cellulose stearoyl triester (CSE) with a high degree of esterification of 2.95, was synthesized and used for the formation of temperature-responsive films. Transparent and hydrophobic thin films were fabricated by dip-coating hydrophilic and hydrophobic surfaces with CSE. The films had thicknesses between 8 and 360 nm, depending on the concentrations of CSE solutions. Static contact angles of water drops on the films were up to 120 degrees. The thin films from CSE solutions in toluene with concentrations of at least 5 mg/mL were not permeable for water molecules, as shown via cyclic voltammetric analysis. Based on film properties and morphologies, different self-assembly mechanisms of CSE films on hydrophilic and hydrophobic surfaces were proposed. In addition, these films showed temperature-responsiveness, which was demonstrated by the temperature-controlled release of rhodamine B molecules from films.