The influence of substituents of cellulose ethers on their interaction with chitosan surfaces

This study investigated how subtle variations in the number of substituent groups in hydroxypropyl methylcellulose (HPMC) affect its interaction with chitosan surfaces. We used a model system with ultra-thin chitosan films on QCM-D sensors to probe the adsorption of various HPMC grades. The HPMCs had similar molecular weights but differed in their degree of substitution, which was shown to affect their solubility. Hansen solubility parameters and dynamic light scattering (DLS) data revealed that lower solubility and higher aggregation led to stronger adsorption. QCM-D measurements confirmed irreversible adsorption for all HPMC variants, with the least soluble grade exhibiting the highest adsorption. These findings demonstrate that lower solubility enhances HPMC adsorption onto chitosan, providing valuable insights for optimizing polymer interactions in applications such as oral film formulations. • Carbohydrate derivatives are key excipients in pharmaceutical formulations. • Subtle changes in HPMC substitution affect solubility and aggregation. • HPMC solubility strongly influences its adsorption onto chitosan surfaces. • A model system reveals irreversible HPMC adsorption on chitosan films. • Findings guide polymer interaction design in pharmaceutical applications.