Tuning crystallization of thin coatings on paper: Impact of cellulose stearoyl ester on wax co-crystallization

Paper-based packaging represents a viable alternative for reducing plastic usage. To tailor material performance, wax coatings with distinct crystallization behaviors are employed. One coating system of particular interest is a blend of low-molecular-weight ethylene glycol distearate (EGDS) and fully substituted cellulose stearoyl ester (CSE). Upon cooling from the melt under ambient conditions, this blend forms superficial crystalline structures on the micrometer scale, enabling its function as a regenerable, superhydrophobic paper coating. This study investigates the co-crystallization behavior of EGDS and CSE, focusing on the spontaneous out-of-plane growth of crystallites without significant energy input. Initially, the crystallization of pure EGDS was characterized. Subsequently, the interaction of EGDS wax with biobased CSE polymer was examined in detail using calorimetric analysis, scattering techniques, and NMR spectroscopy, respectively. The influence of the side chain length of the cellulose ester, and its impact on chemical compatibility with EGDS, was also considered. The system exhibits phase mediation through the insertion of polymeric aliphatic side chains into the EGDS structure and the formation of CSE side-chain crystallites, which serve as nucleation sites for subsequent EGDS crystallization. This allows the controlled tuning of crystalline morphology and thus broaden its applicability in sustainable material development for advanced applications.