Tunable Self-Assembly of Cellulose Nanowhiskers and Polyvinyl Alcohol Chains Induced by Surface Tension Torque

This article focuses on the formation of the surface tension torque (STT) phenomenon close to the dry-line boundary layer during evaporation of the liquid phase of a solution casted shape-anisotropic nanoparticle suspension (here, cellulose nanowhisker (CNW)) or dissolved polymer (here, polyvinyl alcohol (PVA)) and its effects on self-assembly of the cellulose nanocrystals and polymer chains. The results confirm that the STT tends to align both the CNWs and the PVA chains tangential to the dry-line boundary layer. By careful control of the advancement of the dry-line, achieving special linear and curved patterns of both the CNWs and the PVA chains proportional to the mold position and geometry is possible. The STT phenomenon is explained and simplified in terms of a physical model. Understanding of the STT phenomenon and its effects on the alignment and self-assembly of the CNWs and PVA chains is necessary especially when achieving alignment using a modulated external magnetic or electric field is desired. The STT is safe, inexpensive, easy, and efficient, and can be a good alternative to the magnetic and electric field orientation methods.