Efficient Formation of a Carbohydrate-Based Polyelectrolyte Complex Gel with Macroscopic Homogeneity

Biobased polyelectrolyte complexes (BioPECs) have attracted considerable attention due to their unique properties and potential applications in various fields. However, the processability of BioPECs often remains a challenge because of the insolubility of the solution components and of the complex itself. In this study, we develop an alkalinization method for BioPEC complexation, which enables uniform gel complexation from a single-phase precursor solution. The complexation time has been significantly reduced in comparison to a previously developed acidification method. The mechanical properties of BioPECs prepared by both methods were characterized using the quartz crystal microbalance (QCM) and in situ shear rheometry with a porous base plate that was used to study the reversible nature of the complexation process. The difference in local polymer concentration at the substrate surface was determined before and after the complexation. These concentration measurements demonstrate a unique capability of the QCM for determining equilibrium phase behavior in a two-phase polymer solution. Our findings demonstrate the feasibility and advantages of the alkalinization method for fast and scalable BioPEC complexation, which can facilitate the development and application of BioPECs in various fields.