Abstract
Cellulose derivatives are promising raw material as emulsifier, thickening or suspending agent, excipient, drug release agent, adhesive or water-based coating for food, building or pharmaceutical industries. Additives such as plasticizers or surfactants are frequently incorporated into such biopolymers to improve their properties. The aim of this work is to formulate, by introducing dedicated additives, biopolymer films based on cellulose derivatives and to explore their surface properties. The study investigates the influence of hydrophilic and hydrophobic additives on the surface properties of hypromellose films. The surface structure and morphology of hypromellose films shows the presence of nano-clusters, the which disappear as surfactant content increases. So does the surface average roughness and the surface free energy of the formulated films, suggesting the formation of a weak boundary layer at the film surface. As a consequence, a sharp decrease of nano-adhesion and nanofriction forces is observed. Hydrophilic additive induces the swelling of hypromellose clusters and an increase of the film surface free energy as well as nano-friction and nano-adhesion forces. The present study clearly underlines the strong dependence of the surface properties of the formulated films on additive nature and concentration as well as the interplay with additive-biopolymer matrix compatibility. Formulation appears then as an original and simple way to tune and target surface morphology and surface properties of biobased polymer films.
